Dalal Asker - Academia.edu (original) (raw)
Papers by Dalal Asker
Journal of Colloid and Interface Science, 2018
Optimizing the macroscopic properties, shelf-life and stability of emulsion products requires a b... more Optimizing the macroscopic properties, shelf-life and stability of emulsion products requires a better understanding of the microstructural characteristics such as the type (nano, micro and macro) and the relative distribution of components (i.e., oil and surfactant) within the emulsion droplets. We used Diffusion-Ordered NMR Spectroscopy (DOSY NMR) to evaluate these characteristics in model oil-in-water emulsion containing Tween 80 and medium chain triglycerides (MCT). At low MCT concentrations, the solutions were transparent but from 1 to 5 wt% MCT, they became translucent then opaque. 1 wt% MCT was the upper boundary for the appearance of nanoemulsion phase. From the decays of the chemical shift signals of MCT and Tween 80, the DOSY results clearly demonstrate that the self-diffusion coefficients (D) are dependent on oil concentration. Small microemulsion droplets of almost uniform size (d = 12-22 nm) coexist with two sets of large nanoemulsion (d < 200 nm) and emulsion (d > 200 nm) droplets. The large droplets increase significantly in size with increasing MCT. The most striking result is the clear evidence for the presence of microemulsion droplets of nearly uniform size in the aqueous phase from below to above the nanoemulsion transition concentration at 1 wt% MCT.
ACS Applied Materials & Interfaces
Biofilm formation on stainless steel (SS) surfaces of food-processing plants, leading to food-bor... more Biofilm formation on stainless steel (SS) surfaces of food-processing plants, leading to food-borne illness outbreaks, is enabled by the attachment and confinement of pathogens within microscale cavities of surface roughness (grooves, scratches). We report foodsafe oil-based slippery coatings (FOSCs) for food-processing surfaces that suppress bacterial adherence and biofilm formation by trapping residual oil lubricant within these surface cavities to block microbial growth. SS surfaces were chemically functionalized with alkylphosphonic acid to preferentially wet a layer of food-grade oil. FOSCs reduced the effective surface roughness, the adhesion of organic food residue, and bacteria. FOSCs significantly reduced Pseudomonas aeruginosa biofilm formation on standard roughness SS-316 by 5 log CFU cm-2, and by 3 log CFU cm-2 for mirror-finished SS. FOSCs also enhanced surface cleanability, which we measured by bacterial counts after conventional detergent cleaning. Importantly, both SS grades maintained their antibiofilm activity after the erosion of the oil layer by surface wear with glass beads, which suggests that there is a residual volume of oil that remains to block surface cavity defects. These results indicate the potential of such low-cost, scalable approaches to enhance the cleanability of SS food-processing surfaces and improve food safety by reducing biofilm growth.
Methods in molecular biology (Clifton, N.J.), 2012
Zeaxanthin is a powerful antioxidant that is widely found in vegetables and fruits. Epidemiologic... more Zeaxanthin is a powerful antioxidant that is widely found in vegetables and fruits. Epidemiological evidences suggest that increasing the consumption of zeaxanthin in the diet is associated with a lower risk of age-related macular degeneration, helps prevent glaucoma and cataracts, and supports normal eye health. Zeaxanthin is a promising nutraceutical with many applications in the feed, food, and pharmaceutical industries. Currently, the commercial production of zeaxanthin is still dependant on synthetic routes with limitation for the biological one. Nevertheless, the biotechnological production of zeaxanthin is emerging due to its safety, potential large-scale production, and consumers' demand and preference for natural additives. Using a rapid screening method based on 16S rRNA gene and effective high-performance liquid chromatography (HPLC)-Diodearray-MS methods for carotenoids' analysis, we isolated effective zeaxanthin-producing bacteria (strain TDMA-5(T) and -16(T)) t...
Ultrasound is composed of sound waves with frequency beyond the limit of human hearing. By tuning... more Ultrasound is composed of sound waves with frequency beyond the limit of human hearing. By tuning frequency , ultrasound can be utilized in many industrial applications including food. Ultrasound techniques are relatively cheap, simple and energy saving, and thus became an emerging technology for probing and modifying food products. Low power (high frequency) ultrasound is used for monitoring the composition and physicochemical properties of food components and products during processing and storage, which is crucial for controlling the food properties and improving its quality. High power (low frequency) ultrasound, on the other hand, induces mechanical, physical and chemical/biochemical changes through cavitation, which supports many food processing operations such as extraction, freezing, drying, emulsification and inactivation of pathogenic bacteria on food contact surfaces. This review summarizes the major applications of low and high power ultrasound in food science and technology. The basic principles of low and high power ultrasound will be highlighted, and their methods and applications including important research results will be presented. These applications include meat products, vegetables and fruits, cereal products, aerated foods, honey, food gels, food proteins, food enzymes, microbial inactivation, freezing, drying and extraction. Published by Elsevier Ltd.
Langmuir, 2009
Lauric arginate (LAE), a cationic surfactant, is a highly potent food-grade antimicrobial that is... more Lauric arginate (LAE), a cationic surfactant, is a highly potent food-grade antimicrobial that is active against a wide range of food pathogens and spoilage organisms. In compositionally complex environments, the antimicrobial activity of cationic LAE is likely to be impacted by its interactions with anionic components. The purpose of this study was to characterize the interactions between cationic LAE and an anionic biopolymer (high methoxyl pectin, HMP) using isothermal titration calorimetry (ITC), microelectrophoresis (ME), and turbidity measurements. ITC and ME measurements indicated that LAE bound to pectin, while turbidity measurements indicated that the complexes formed could be either soluble or insoluble depending on solution composition. In the absence of pectin, the critical micelle concentration (CMC) of LAE determined by ITC at 25 degrees C was 0.21% (w/v). The amount of LAE bound per unit amount of pectin decreased with increasing pectin concentration (from 1.5 to 0.5 g/g for 0.05 to 0.5 wt % pectin) and with increasing temperature (from 1.7 to 1.3 g/g for 15 to 40 degrees C). The binding contribution to the LAE-pectin interaction was exothermic and was attributed to electrostatic attraction between the cationic surfactant and anionic biopolymer. This study demonstrates that lauric arginate can form either soluble or insoluble complexes with anionic biopolymers depending on the composition of the system.
Langmuir, 2009
Lauric arginate (LAE), a cationic surfactant, is a highly potent food-grade antimicrobial that is... more Lauric arginate (LAE), a cationic surfactant, is a highly potent food-grade antimicrobial that is active against a wide range of food pathogens and spoilage organisms. In compositionally complex environments, the antimicrobial activity of cationic LAE is likely to be impacted by its interactions with anionic components. The purpose of this study was to characterize the interactions between cationic LAE and an anionic biopolymer (high methoxyl pectin, HMP) using isothermal titration calorimetry (ITC), microelectrophoresis (ME), and turbidity measurements. ITC and ME measurements indicated that LAE bound to pectin, while turbidity measurements indicated that the complexes formed could be either soluble or insoluble depending on solution composition. In the absence of pectin, the critical micelle concentration (CMC) of LAE determined by ITC at 25 degrees C was 0.21% (w/v). The amount of LAE bound per unit amount of pectin decreased with increasing pectin concentration (from 1.5 to 0.5 g/g for 0.05 to 0.5 wt % pectin) and with increasing temperature (from 1.7 to 1.3 g/g for 15 to 40 degrees C). The binding contribution to the LAE-pectin interaction was exothermic and was attributed to electrostatic attraction between the cationic surfactant and anionic biopolymer. This study demonstrates that lauric arginate can form either soluble or insoluble complexes with anionic biopolymers depending on the composition of the system.
Journal of Bioscience and Bioengineering, 1999
... In Krieg, 28. ed.), Bergey's manual of systematic bacteriology. Wil Wilkins, Baltimo... more ... In Krieg, 28. ed.), Bergey's manual of systematic bacteriology. Wil Wilkins, Baltimore (1984). 15. ... Biotechnol. Tech., 4, 107112 (1990). 22. Onishi, H., McCance, ME, and Gibbons, NE: A synthetic medium for extremely halophilic bacteria. Canad. J. Microbiol., 11, 365373 (1965). ...
Canadian Journal of Microbiology, 2002
Based on the amplification of a 16S rDNA, a PCR assay for the identification of species of Halofe... more Based on the amplification of a 16S rDNA, a PCR assay for the identification of species of Haloferax to genus level was performed. Two variable regions of the 16S rDNA in Haloferax spp. were selected as genus-specific primers for the PCR assay and hybridization probe. Five genera of halophilic Archaea and Escherichia coli were examined as outside groups. Using this approach, all strains of Haloferax spp. were positive. In contrast, all species belonging to the most closely related genera, including Natrinema, Halorubrum, Halobacterium, and Haloarcula, were negative. In addition, the mass bloom of halophilic Archaea that develops in the El-Mallahet saltern of Alexandria City was positive using the same approach. This assay, which does not require pure cultures of microorganisms, is a specific and rapid method for identifying Haloferax spp. in hypersaline environments.
International Journal of Systematic and Evolutionary Microbiology, 2002
An extremely halophilic red micro-organism designated strain TM T was isolated from a solar salte... more An extremely halophilic red micro-organism designated strain TM T was isolated from a solar saltern in Alexandria, Egypt. The micro-organism stains Gramnegative, is very pleomorphic, non-motile and strictly aerobic and requires at least 10 g NaCl l N1 for growth. The growth optimum is 250 g NaCl l N1 . Growth is also observed over a wide range of MgSO 4 concentrations (10-40 g l N1 ). Aerobic reduction of nitrate without gas production was detected. Cells grew aerobically in a minimal salts medium containing ammonium chloride and glucose. Strain TM T produced acid from fructose, glucose, rhamnose, maltose and glycerol. The GMC content of the DNA was 595O03 mol %. On the basis of polar lipid analysis, the isolate belonged to the genus Haloferax. Analysis of the 16S rDNA sequence showed the highest similarity (S 99 %) to be to the type strain Haloferax volcanii. Although the spectrum of antibiotic susceptibility was similar to that of validly described species of the genus Haloferax, the strain could be distinguished from them by its different response to josamycin and rifampicin. Strain TM T is unique within the genus Haloferax in producing canthaxanthin. Comparative analysis of phenotypic properties and DNA-DNA hybridization between strain TM T and Haloferax species supported the conclusion that TM T is a novel species within this genus, for which the name Haloferax alexandrinus sp. nov. is proposed. The type strain is TM T (l JCM 10717 T l IFO 16590 T ).
Journal of Bioscience and Bioengineering, 2002
The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Halof... more The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Haloferax alexandrinus strain TM(T), were investigated using thin-layer chromatography (TLC), spectrophotometry, electron ionization-mass spectroscopy (EI-MS), fast atom bombardment mass spectrometry (FAB-MS), nuclear magnetic response spectrometry (13C-NMR) and high performance liquid chromatography (HPLC). This archaeon appeared to contain diphytanyl diether lipids (C20-C20) as core lipids. The major phospholipids were found to be phosphatidylglycero-phosphate-methyl ester (PGP-Me) and phosphatidylglycerol (PG), but no phosphatidylglycero-sulfate was detected. The strain contained two glycolipids, sulfated diglycosyl diether (S-DGD-1) and unsulfated diglycosyl diether (DGD). Analysis of the non polar lipids revealed the presence of beta-carotene, 3-hydroxyechinenone, gamma-carotene, cis-astaxanthin, lycopene, trisanhydro-bacterioruberin,monanhydro-bacterioruberin, bacterioruberin isomer, bacterioruberin and canthaxanthin. Although the polar lipids profile of Hfx. alexandrinus strain TM(T) was similar to those of other species of the genus Haloferax, the non polar lipid (carotenoids) profile was markedly different. Further experiments on the influence of NaCl concentration on the lipids composition of Hfx. alexandrinus strain TM(T) demonstrated the dependence of the proportion of each of bacterioruberin, beta-carotene and canthaxanthin on the NaCl concentration in the growth media.
Journal of Bioscience and Bioengineering, 2002
The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Halof... more The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Haloferax alexandrinus strain TM(T), were investigated using thin-layer chromatography (TLC), spectrophotometry, electron ionization-mass spectroscopy (EI-MS), fast atom bombardment mass spectrometry (FAB-MS), nuclear magnetic response spectrometry (13C-NMR) and high performance liquid chromatography (HPLC). This archaeon appeared to contain diphytanyl diether lipids (C20-C20) as core lipids. The major phospholipids were found to be phosphatidylglycero-phosphate-methyl ester (PGP-Me) and phosphatidylglycerol (PG), but no phosphatidylglycero-sulfate was detected. The strain contained two glycolipids, sulfated diglycosyl diether (S-DGD-1) and unsulfated diglycosyl diether (DGD). Analysis of the non polar lipids revealed the presence of beta-carotene, 3-hydroxyechinenone, gamma-carotene, cis-astaxanthin, lycopene, trisanhydro-bacterioruberin,monanhydro-bacterioruberin, bacterioruberin isomer, bacterioruberin and canthaxanthin. Although the polar lipids profile of Hfx. alexandrinus strain TM(T) was similar to those of other species of the genus Haloferax, the non polar lipid (carotenoids) profile was markedly different. Further experiments on the influence of NaCl concentration on the lipids composition of Hfx. alexandrinus strain TM(T) demonstrated the dependence of the proportion of each of bacterioruberin, beta-carotene and canthaxanthin on the NaCl concentration in the growth media.
Applied Microbiology and Biotechnology, 2002
The production of carotenoids from Haloferax alexandrinus strain TMT was investigated at various ... more The production of carotenoids from Haloferax alexandrinus strain TMT was investigated at various concentrations of NaCl (10–25%) in culture media under non-aseptic conditions. PCR and dot blot hybridization assays were employed to monitor the growth of Hfx. alexandrinus in the culture under aseptic and non-aseptic conditions. The amplified PCR products of 16S rDNA from Hfx. alexandrinus grown under aseptic conditions were used as specific probes, which bound with amplified PCR products of 16S rDNA dots from both aseptic and non-aseptic conditions (20–25% NaCl). The results indicated that contamination of the culture was precluded at high NaCl concentrations (20–25%). Therefore, it is not necessary to perform asepsis during the biotechnological processes of carotenoid production by Hfx. alexandrinus. A 1-l-scale cultivation of the cells in flask cultures under non-aseptic conditions produced 3.12±0.5 g dry weight, 6.34±2.5 mg total carotenoids and 2,156.67±0.1 µg canthaxanthin. Further experiments in a batch fermenter, under non-aseptic conditions, also demonstrated increases in the biomass concentration and carotenoid production. When grown in a standard growth medium at 25% NaCl, the cells of Hfx. alexandrinus lysed spontaneously in fresh water and hence carotenoids could be extracted directly from the cells without any mechanical disintegration. These results demonstrate the feasibility and simplicity of commercial production of carotenoids using Hfx. alexandrinus.
International Journal of Systematic and Evolutionary Microbiology, 2009
A gamma-and UV-radiation-tolerant, pale-pink strain (TDMA-uv53 T ) was isolated from a freshwater... more A gamma-and UV-radiation-tolerant, pale-pink strain (TDMA-uv53 T ) was isolated from a freshwater sample collected at Misasa (Tottori, Japan), after exposure of the water sample to UV radiation. The cells stained Gram-positive and were non-motile, rod-shaped and non-sporeforming. The DNA G+C content of the strain was 69.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain TDMA-uv53 T belongs to the genus Deinococcus, the highest sequence similarities being found with Deinococcus claudionis PO-04-19-125 T (96 %), D. altitudinis ME-04-01-32 T (96 %), D. radiomollis PO-04-20-132 T (95 %), D. deserti VCD115 T (91.5 %), D. hopiensis KR-140 T (91.0 %) and D. sonorensis KR-87 T (91.0 %). Major fatty acids were iso-15 : 0, 15 : 1v6c, 15 : 0, 16 : 0 and summed feature 3 (iso-15 : 0 2-OH and/or 16 : 1v7c). MK-8 was the predominant respiratory quinone. Phylogenetic distinctiveness and unique phenotypic characteristics differentiated strain TDMA-uv53 T from closely related Deinococcus species. The results of our polyphasic taxonomic analyses suggested that TDMA-uv53 T represents a novel Deinococcus species, for which the name Deinococcus aquiradiocola sp. nov. is proposed. The type strain is TDMA-uv53 T (5JCM 14370 T 5NBRC 102118 T 5CCUG 53612 T ).
International Journal of Systematic and Evolutionary Microbiology, 2010
Four gamma-and UV-radiation-resistant bacterial strains, designated TDMA-24 T , TDMA-24-2, TDMA-2... more Four gamma-and UV-radiation-resistant bacterial strains, designated TDMA-24 T , TDMA-24-2, TDMA-24-3 and TDMA-24-4, were isolated from a fresh-water sample collected at Misasa, Tottori, Japan. Cells of these strains were Gram-reaction-positive, non-motile, non-spore-forming, rod-shaped and formed red colonies. The genomic DNA G+C contents ranged from 70.5 to 70.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel isolates belong to the genus Deinococcus, the highest sequence similarities being with Deinococcus aquaticus PB314 T (98 %) and Deinococcus caeni Ho-08 T (97 %). The polar lipid profile of strain TDMA-24 T comprised three unidentified phosphoglycolipids, five unidentified glycolipids and seven unidentified polar lipids. MK-8 was the predominant respiratory quinone. Major fatty acids were iso-C 15 : 0 , C 15 : 1 v6c, C 15 : 0 , C 16 : 0 and summed feature 3 (iso-C 15 : 0 2-OH and/or C 16 : 1 v7c). On the basis of their phylogenetic positions and chemotaxonomic and phenotypic characteristics, the novel isolates represent a novel species of the genus Deinococcus, for which the name Deinococcus depolymerans sp. nov. is proposed. The type strain is TDMA
Cheminform, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
International Journal of Systematic and Evolutionary Microbiology, 2007
A yellow-pigmented, Gram-negative, motile, strictly aerobic, pleomorphic bacterium (strain TDMA-1... more A yellow-pigmented, Gram-negative, motile, strictly aerobic, pleomorphic bacterium (strain TDMA-16 T ) was isolated from a freshwater sample collected at Misasa (Tottori, Japan). Strain TDMA-16 T was slightly tolerant to gamma-ray irradiation and produced carotenoids, including zeaxanthin, nostoxanthin and an unknown carotenoid, effectively [1.7 mg (g dry cells) "1 ]. The DNA G+C content of strain TDMA-16 T was 63.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences placed strain TDMA-16 T in a distinct lineage in the family Sphingomonadaceae; sequence data showed that strain TDMA-16 T was most closely related to Sphingomonas mali IFO 15500 T (95.1 %), Sphingomonas aquatilis JSS7 T (95.0 %), Sphingomonas pruni IFO 15498 T (94.9 %), Sphingomonas melonis DSM 14444 T (94.9 %) and Sphingomonas asaccharolytica IFO 15499 T (94.5 %). The major fatty acids of strain TDMA-16 T were C 17 : 1 v6c (34.5 %) and C 18 : 1 v7c (29.3 %). The presence of Q-10 as the main ubiquinone, the Sphingomonadaceaespecific sphingoglycolipid in the polar lipid profile and 2-hydroxy fatty acids, plus the absence of 3-hydroxy fatty acids, supported identification of this strain as a member of the genus Sphingomonas sensu stricto. Phylogenetic distinctiveness and unique phenotypic characteristics differentiated strain TDMA-16 T from closely related Sphingomonas species. The results of polyphasic taxonomic analyses suggest that strain TDMA-16 T represents a novel Sphingomonas species, for which the name Sphingomonas jaspsi sp. nov. is proposed. The type strain is strain TDMA-16 T (=NBRC 102120 T =DSM 18422 T =CCUG 53607 T ).
Systematic and Applied Microbiology, 2007
Journal of Industrial Microbiology & Biotechnology, 2006
Carotenoids are naturally occurring yellow or orange pigments that serve as a protectant against ... more Carotenoids are naturally occurring yellow or orange pigments that serve as a protectant against photo-oxidative damages. Among the wide variety of producers, the prokaryotes generate a broad spectrum of carotenoids with diverse chemical structures that are expected to have a high potential in biotechnological applications. Bacterial carotenogenesis occurs in a constitutive or light-induced manner, which suggests the diversity of the regulatory mechanism. The mechanism for light-induced carotenoid production in non-phototrophic bacteria has been studied in detail in Myxococcus xanthus, a Gram-negative gliding bacterium. The complicated mechanism involves the activation of an extracytoplasmic function (ECF) sigma factor (CarQ), which leads to the sequestration of a MerR family transcriptional regulator (CarA) that represses the expression of the carotenoid biosynthesis genes in the dark. Recently, we identified another regulatory mechanism for light-induced carotenogenesis in Streptomyces coelicolor A3(2), a Gram-positive soil bacterium. In this organism, the transcription of the carotenoid biosynthesis gene cluster is specified by LitS, a photo-inducible ECF sigma factor. The evidence indicates that the photo-dependent transcription of litS is mediated by LitR, a MerR family transcriptional regulator. In addition, it is suggested that the conformational alteration of LitR upon receiving the illumination signal determines its binding to DNA. The carboxy-terminal domain of LitR contains a possible binding site for Vitamin B12, which may serve as a capturing apparatus for the illumination signal.
Journal of Antibiotics, 2009
Applied Microbiology and Biotechnology, 2007
We obtained carotenoid-producing microorganisms at a high frequency from water samples collected ... more We obtained carotenoid-producing microorganisms at a high frequency from water samples collected at Misasa (Tottori, Japan), a region known for its high natural radioactivity content. A comprehensive 16S rRNA gene-based phylogenetic analysis revealed that the 104 potential carotenoid producers isolated from Misasa could be classified into 38 different species belonging to seven bacterial classes (Flavobacteria, Sphingobacteria, α-Proteobacteria, γ-Proteobacteria, Deinococci, Actinobacteria, and Bacilli). Of these 38 species, 14 showed sequence similarities less than 97% to their closest identified relatives, and 9 were related to genera that have not been described earlier in terms of carotenoid production. The red-pigmented isolates belonging to Deinococci showed marked resistance to γ rays and UV irradiation, while those related to Sphingomonas showed weak resistance. The carotenoids produced by the isolates were zeaxanthin (6 strains), dihydroxyastaxanthin (24 strains), astaxanthin (27 strains), canthaxanthin (10 strains), and unidentified molecular species that were produced by the isolates related to Deinococcus, Exiguobacterium, and Flectobacillus. UV irradiation would be useful for the selective isolation of carotenoid-producing microorganisms, and that new microbial producers and other molecular species of carotenoids may potentially be identified from radioactive environments.
Journal of Colloid and Interface Science, 2018
Optimizing the macroscopic properties, shelf-life and stability of emulsion products requires a b... more Optimizing the macroscopic properties, shelf-life and stability of emulsion products requires a better understanding of the microstructural characteristics such as the type (nano, micro and macro) and the relative distribution of components (i.e., oil and surfactant) within the emulsion droplets. We used Diffusion-Ordered NMR Spectroscopy (DOSY NMR) to evaluate these characteristics in model oil-in-water emulsion containing Tween 80 and medium chain triglycerides (MCT). At low MCT concentrations, the solutions were transparent but from 1 to 5 wt% MCT, they became translucent then opaque. 1 wt% MCT was the upper boundary for the appearance of nanoemulsion phase. From the decays of the chemical shift signals of MCT and Tween 80, the DOSY results clearly demonstrate that the self-diffusion coefficients (D) are dependent on oil concentration. Small microemulsion droplets of almost uniform size (d = 12-22 nm) coexist with two sets of large nanoemulsion (d < 200 nm) and emulsion (d > 200 nm) droplets. The large droplets increase significantly in size with increasing MCT. The most striking result is the clear evidence for the presence of microemulsion droplets of nearly uniform size in the aqueous phase from below to above the nanoemulsion transition concentration at 1 wt% MCT.
ACS Applied Materials & Interfaces
Biofilm formation on stainless steel (SS) surfaces of food-processing plants, leading to food-bor... more Biofilm formation on stainless steel (SS) surfaces of food-processing plants, leading to food-borne illness outbreaks, is enabled by the attachment and confinement of pathogens within microscale cavities of surface roughness (grooves, scratches). We report foodsafe oil-based slippery coatings (FOSCs) for food-processing surfaces that suppress bacterial adherence and biofilm formation by trapping residual oil lubricant within these surface cavities to block microbial growth. SS surfaces were chemically functionalized with alkylphosphonic acid to preferentially wet a layer of food-grade oil. FOSCs reduced the effective surface roughness, the adhesion of organic food residue, and bacteria. FOSCs significantly reduced Pseudomonas aeruginosa biofilm formation on standard roughness SS-316 by 5 log CFU cm-2, and by 3 log CFU cm-2 for mirror-finished SS. FOSCs also enhanced surface cleanability, which we measured by bacterial counts after conventional detergent cleaning. Importantly, both SS grades maintained their antibiofilm activity after the erosion of the oil layer by surface wear with glass beads, which suggests that there is a residual volume of oil that remains to block surface cavity defects. These results indicate the potential of such low-cost, scalable approaches to enhance the cleanability of SS food-processing surfaces and improve food safety by reducing biofilm growth.
Methods in molecular biology (Clifton, N.J.), 2012
Zeaxanthin is a powerful antioxidant that is widely found in vegetables and fruits. Epidemiologic... more Zeaxanthin is a powerful antioxidant that is widely found in vegetables and fruits. Epidemiological evidences suggest that increasing the consumption of zeaxanthin in the diet is associated with a lower risk of age-related macular degeneration, helps prevent glaucoma and cataracts, and supports normal eye health. Zeaxanthin is a promising nutraceutical with many applications in the feed, food, and pharmaceutical industries. Currently, the commercial production of zeaxanthin is still dependant on synthetic routes with limitation for the biological one. Nevertheless, the biotechnological production of zeaxanthin is emerging due to its safety, potential large-scale production, and consumers' demand and preference for natural additives. Using a rapid screening method based on 16S rRNA gene and effective high-performance liquid chromatography (HPLC)-Diodearray-MS methods for carotenoids' analysis, we isolated effective zeaxanthin-producing bacteria (strain TDMA-5(T) and -16(T)) t...
Ultrasound is composed of sound waves with frequency beyond the limit of human hearing. By tuning... more Ultrasound is composed of sound waves with frequency beyond the limit of human hearing. By tuning frequency , ultrasound can be utilized in many industrial applications including food. Ultrasound techniques are relatively cheap, simple and energy saving, and thus became an emerging technology for probing and modifying food products. Low power (high frequency) ultrasound is used for monitoring the composition and physicochemical properties of food components and products during processing and storage, which is crucial for controlling the food properties and improving its quality. High power (low frequency) ultrasound, on the other hand, induces mechanical, physical and chemical/biochemical changes through cavitation, which supports many food processing operations such as extraction, freezing, drying, emulsification and inactivation of pathogenic bacteria on food contact surfaces. This review summarizes the major applications of low and high power ultrasound in food science and technology. The basic principles of low and high power ultrasound will be highlighted, and their methods and applications including important research results will be presented. These applications include meat products, vegetables and fruits, cereal products, aerated foods, honey, food gels, food proteins, food enzymes, microbial inactivation, freezing, drying and extraction. Published by Elsevier Ltd.
Langmuir, 2009
Lauric arginate (LAE), a cationic surfactant, is a highly potent food-grade antimicrobial that is... more Lauric arginate (LAE), a cationic surfactant, is a highly potent food-grade antimicrobial that is active against a wide range of food pathogens and spoilage organisms. In compositionally complex environments, the antimicrobial activity of cationic LAE is likely to be impacted by its interactions with anionic components. The purpose of this study was to characterize the interactions between cationic LAE and an anionic biopolymer (high methoxyl pectin, HMP) using isothermal titration calorimetry (ITC), microelectrophoresis (ME), and turbidity measurements. ITC and ME measurements indicated that LAE bound to pectin, while turbidity measurements indicated that the complexes formed could be either soluble or insoluble depending on solution composition. In the absence of pectin, the critical micelle concentration (CMC) of LAE determined by ITC at 25 degrees C was 0.21% (w/v). The amount of LAE bound per unit amount of pectin decreased with increasing pectin concentration (from 1.5 to 0.5 g/g for 0.05 to 0.5 wt % pectin) and with increasing temperature (from 1.7 to 1.3 g/g for 15 to 40 degrees C). The binding contribution to the LAE-pectin interaction was exothermic and was attributed to electrostatic attraction between the cationic surfactant and anionic biopolymer. This study demonstrates that lauric arginate can form either soluble or insoluble complexes with anionic biopolymers depending on the composition of the system.
Langmuir, 2009
Lauric arginate (LAE), a cationic surfactant, is a highly potent food-grade antimicrobial that is... more Lauric arginate (LAE), a cationic surfactant, is a highly potent food-grade antimicrobial that is active against a wide range of food pathogens and spoilage organisms. In compositionally complex environments, the antimicrobial activity of cationic LAE is likely to be impacted by its interactions with anionic components. The purpose of this study was to characterize the interactions between cationic LAE and an anionic biopolymer (high methoxyl pectin, HMP) using isothermal titration calorimetry (ITC), microelectrophoresis (ME), and turbidity measurements. ITC and ME measurements indicated that LAE bound to pectin, while turbidity measurements indicated that the complexes formed could be either soluble or insoluble depending on solution composition. In the absence of pectin, the critical micelle concentration (CMC) of LAE determined by ITC at 25 degrees C was 0.21% (w/v). The amount of LAE bound per unit amount of pectin decreased with increasing pectin concentration (from 1.5 to 0.5 g/g for 0.05 to 0.5 wt % pectin) and with increasing temperature (from 1.7 to 1.3 g/g for 15 to 40 degrees C). The binding contribution to the LAE-pectin interaction was exothermic and was attributed to electrostatic attraction between the cationic surfactant and anionic biopolymer. This study demonstrates that lauric arginate can form either soluble or insoluble complexes with anionic biopolymers depending on the composition of the system.
Journal of Bioscience and Bioengineering, 1999
... In Krieg, 28. ed.), Bergey's manual of systematic bacteriology. Wil Wilkins, Baltimo... more ... In Krieg, 28. ed.), Bergey's manual of systematic bacteriology. Wil Wilkins, Baltimore (1984). 15. ... Biotechnol. Tech., 4, 107112 (1990). 22. Onishi, H., McCance, ME, and Gibbons, NE: A synthetic medium for extremely halophilic bacteria. Canad. J. Microbiol., 11, 365373 (1965). ...
Canadian Journal of Microbiology, 2002
Based on the amplification of a 16S rDNA, a PCR assay for the identification of species of Halofe... more Based on the amplification of a 16S rDNA, a PCR assay for the identification of species of Haloferax to genus level was performed. Two variable regions of the 16S rDNA in Haloferax spp. were selected as genus-specific primers for the PCR assay and hybridization probe. Five genera of halophilic Archaea and Escherichia coli were examined as outside groups. Using this approach, all strains of Haloferax spp. were positive. In contrast, all species belonging to the most closely related genera, including Natrinema, Halorubrum, Halobacterium, and Haloarcula, were negative. In addition, the mass bloom of halophilic Archaea that develops in the El-Mallahet saltern of Alexandria City was positive using the same approach. This assay, which does not require pure cultures of microorganisms, is a specific and rapid method for identifying Haloferax spp. in hypersaline environments.
International Journal of Systematic and Evolutionary Microbiology, 2002
An extremely halophilic red micro-organism designated strain TM T was isolated from a solar salte... more An extremely halophilic red micro-organism designated strain TM T was isolated from a solar saltern in Alexandria, Egypt. The micro-organism stains Gramnegative, is very pleomorphic, non-motile and strictly aerobic and requires at least 10 g NaCl l N1 for growth. The growth optimum is 250 g NaCl l N1 . Growth is also observed over a wide range of MgSO 4 concentrations (10-40 g l N1 ). Aerobic reduction of nitrate without gas production was detected. Cells grew aerobically in a minimal salts medium containing ammonium chloride and glucose. Strain TM T produced acid from fructose, glucose, rhamnose, maltose and glycerol. The GMC content of the DNA was 595O03 mol %. On the basis of polar lipid analysis, the isolate belonged to the genus Haloferax. Analysis of the 16S rDNA sequence showed the highest similarity (S 99 %) to be to the type strain Haloferax volcanii. Although the spectrum of antibiotic susceptibility was similar to that of validly described species of the genus Haloferax, the strain could be distinguished from them by its different response to josamycin and rifampicin. Strain TM T is unique within the genus Haloferax in producing canthaxanthin. Comparative analysis of phenotypic properties and DNA-DNA hybridization between strain TM T and Haloferax species supported the conclusion that TM T is a novel species within this genus, for which the name Haloferax alexandrinus sp. nov. is proposed. The type strain is TM T (l JCM 10717 T l IFO 16590 T ).
Journal of Bioscience and Bioengineering, 2002
The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Halof... more The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Haloferax alexandrinus strain TM(T), were investigated using thin-layer chromatography (TLC), spectrophotometry, electron ionization-mass spectroscopy (EI-MS), fast atom bombardment mass spectrometry (FAB-MS), nuclear magnetic response spectrometry (13C-NMR) and high performance liquid chromatography (HPLC). This archaeon appeared to contain diphytanyl diether lipids (C20-C20) as core lipids. The major phospholipids were found to be phosphatidylglycero-phosphate-methyl ester (PGP-Me) and phosphatidylglycerol (PG), but no phosphatidylglycero-sulfate was detected. The strain contained two glycolipids, sulfated diglycosyl diether (S-DGD-1) and unsulfated diglycosyl diether (DGD). Analysis of the non polar lipids revealed the presence of beta-carotene, 3-hydroxyechinenone, gamma-carotene, cis-astaxanthin, lycopene, trisanhydro-bacterioruberin,monanhydro-bacterioruberin, bacterioruberin isomer, bacterioruberin and canthaxanthin. Although the polar lipids profile of Hfx. alexandrinus strain TM(T) was similar to those of other species of the genus Haloferax, the non polar lipid (carotenoids) profile was markedly different. Further experiments on the influence of NaCl concentration on the lipids composition of Hfx. alexandrinus strain TM(T) demonstrated the dependence of the proportion of each of bacterioruberin, beta-carotene and canthaxanthin on the NaCl concentration in the growth media.
Journal of Bioscience and Bioengineering, 2002
The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Halof... more The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Haloferax alexandrinus strain TM(T), were investigated using thin-layer chromatography (TLC), spectrophotometry, electron ionization-mass spectroscopy (EI-MS), fast atom bombardment mass spectrometry (FAB-MS), nuclear magnetic response spectrometry (13C-NMR) and high performance liquid chromatography (HPLC). This archaeon appeared to contain diphytanyl diether lipids (C20-C20) as core lipids. The major phospholipids were found to be phosphatidylglycero-phosphate-methyl ester (PGP-Me) and phosphatidylglycerol (PG), but no phosphatidylglycero-sulfate was detected. The strain contained two glycolipids, sulfated diglycosyl diether (S-DGD-1) and unsulfated diglycosyl diether (DGD). Analysis of the non polar lipids revealed the presence of beta-carotene, 3-hydroxyechinenone, gamma-carotene, cis-astaxanthin, lycopene, trisanhydro-bacterioruberin,monanhydro-bacterioruberin, bacterioruberin isomer, bacterioruberin and canthaxanthin. Although the polar lipids profile of Hfx. alexandrinus strain TM(T) was similar to those of other species of the genus Haloferax, the non polar lipid (carotenoids) profile was markedly different. Further experiments on the influence of NaCl concentration on the lipids composition of Hfx. alexandrinus strain TM(T) demonstrated the dependence of the proportion of each of bacterioruberin, beta-carotene and canthaxanthin on the NaCl concentration in the growth media.
Applied Microbiology and Biotechnology, 2002
The production of carotenoids from Haloferax alexandrinus strain TMT was investigated at various ... more The production of carotenoids from Haloferax alexandrinus strain TMT was investigated at various concentrations of NaCl (10–25%) in culture media under non-aseptic conditions. PCR and dot blot hybridization assays were employed to monitor the growth of Hfx. alexandrinus in the culture under aseptic and non-aseptic conditions. The amplified PCR products of 16S rDNA from Hfx. alexandrinus grown under aseptic conditions were used as specific probes, which bound with amplified PCR products of 16S rDNA dots from both aseptic and non-aseptic conditions (20–25% NaCl). The results indicated that contamination of the culture was precluded at high NaCl concentrations (20–25%). Therefore, it is not necessary to perform asepsis during the biotechnological processes of carotenoid production by Hfx. alexandrinus. A 1-l-scale cultivation of the cells in flask cultures under non-aseptic conditions produced 3.12±0.5 g dry weight, 6.34±2.5 mg total carotenoids and 2,156.67±0.1 µg canthaxanthin. Further experiments in a batch fermenter, under non-aseptic conditions, also demonstrated increases in the biomass concentration and carotenoid production. When grown in a standard growth medium at 25% NaCl, the cells of Hfx. alexandrinus lysed spontaneously in fresh water and hence carotenoids could be extracted directly from the cells without any mechanical disintegration. These results demonstrate the feasibility and simplicity of commercial production of carotenoids using Hfx. alexandrinus.
International Journal of Systematic and Evolutionary Microbiology, 2009
A gamma-and UV-radiation-tolerant, pale-pink strain (TDMA-uv53 T ) was isolated from a freshwater... more A gamma-and UV-radiation-tolerant, pale-pink strain (TDMA-uv53 T ) was isolated from a freshwater sample collected at Misasa (Tottori, Japan), after exposure of the water sample to UV radiation. The cells stained Gram-positive and were non-motile, rod-shaped and non-sporeforming. The DNA G+C content of the strain was 69.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain TDMA-uv53 T belongs to the genus Deinococcus, the highest sequence similarities being found with Deinococcus claudionis PO-04-19-125 T (96 %), D. altitudinis ME-04-01-32 T (96 %), D. radiomollis PO-04-20-132 T (95 %), D. deserti VCD115 T (91.5 %), D. hopiensis KR-140 T (91.0 %) and D. sonorensis KR-87 T (91.0 %). Major fatty acids were iso-15 : 0, 15 : 1v6c, 15 : 0, 16 : 0 and summed feature 3 (iso-15 : 0 2-OH and/or 16 : 1v7c). MK-8 was the predominant respiratory quinone. Phylogenetic distinctiveness and unique phenotypic characteristics differentiated strain TDMA-uv53 T from closely related Deinococcus species. The results of our polyphasic taxonomic analyses suggested that TDMA-uv53 T represents a novel Deinococcus species, for which the name Deinococcus aquiradiocola sp. nov. is proposed. The type strain is TDMA-uv53 T (5JCM 14370 T 5NBRC 102118 T 5CCUG 53612 T ).
International Journal of Systematic and Evolutionary Microbiology, 2010
Four gamma-and UV-radiation-resistant bacterial strains, designated TDMA-24 T , TDMA-24-2, TDMA-2... more Four gamma-and UV-radiation-resistant bacterial strains, designated TDMA-24 T , TDMA-24-2, TDMA-24-3 and TDMA-24-4, were isolated from a fresh-water sample collected at Misasa, Tottori, Japan. Cells of these strains were Gram-reaction-positive, non-motile, non-spore-forming, rod-shaped and formed red colonies. The genomic DNA G+C contents ranged from 70.5 to 70.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel isolates belong to the genus Deinococcus, the highest sequence similarities being with Deinococcus aquaticus PB314 T (98 %) and Deinococcus caeni Ho-08 T (97 %). The polar lipid profile of strain TDMA-24 T comprised three unidentified phosphoglycolipids, five unidentified glycolipids and seven unidentified polar lipids. MK-8 was the predominant respiratory quinone. Major fatty acids were iso-C 15 : 0 , C 15 : 1 v6c, C 15 : 0 , C 16 : 0 and summed feature 3 (iso-C 15 : 0 2-OH and/or C 16 : 1 v7c). On the basis of their phylogenetic positions and chemotaxonomic and phenotypic characteristics, the novel isolates represent a novel species of the genus Deinococcus, for which the name Deinococcus depolymerans sp. nov. is proposed. The type strain is TDMA
Cheminform, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
International Journal of Systematic and Evolutionary Microbiology, 2007
A yellow-pigmented, Gram-negative, motile, strictly aerobic, pleomorphic bacterium (strain TDMA-1... more A yellow-pigmented, Gram-negative, motile, strictly aerobic, pleomorphic bacterium (strain TDMA-16 T ) was isolated from a freshwater sample collected at Misasa (Tottori, Japan). Strain TDMA-16 T was slightly tolerant to gamma-ray irradiation and produced carotenoids, including zeaxanthin, nostoxanthin and an unknown carotenoid, effectively [1.7 mg (g dry cells) "1 ]. The DNA G+C content of strain TDMA-16 T was 63.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences placed strain TDMA-16 T in a distinct lineage in the family Sphingomonadaceae; sequence data showed that strain TDMA-16 T was most closely related to Sphingomonas mali IFO 15500 T (95.1 %), Sphingomonas aquatilis JSS7 T (95.0 %), Sphingomonas pruni IFO 15498 T (94.9 %), Sphingomonas melonis DSM 14444 T (94.9 %) and Sphingomonas asaccharolytica IFO 15499 T (94.5 %). The major fatty acids of strain TDMA-16 T were C 17 : 1 v6c (34.5 %) and C 18 : 1 v7c (29.3 %). The presence of Q-10 as the main ubiquinone, the Sphingomonadaceaespecific sphingoglycolipid in the polar lipid profile and 2-hydroxy fatty acids, plus the absence of 3-hydroxy fatty acids, supported identification of this strain as a member of the genus Sphingomonas sensu stricto. Phylogenetic distinctiveness and unique phenotypic characteristics differentiated strain TDMA-16 T from closely related Sphingomonas species. The results of polyphasic taxonomic analyses suggest that strain TDMA-16 T represents a novel Sphingomonas species, for which the name Sphingomonas jaspsi sp. nov. is proposed. The type strain is strain TDMA-16 T (=NBRC 102120 T =DSM 18422 T =CCUG 53607 T ).
Systematic and Applied Microbiology, 2007
Journal of Industrial Microbiology & Biotechnology, 2006
Carotenoids are naturally occurring yellow or orange pigments that serve as a protectant against ... more Carotenoids are naturally occurring yellow or orange pigments that serve as a protectant against photo-oxidative damages. Among the wide variety of producers, the prokaryotes generate a broad spectrum of carotenoids with diverse chemical structures that are expected to have a high potential in biotechnological applications. Bacterial carotenogenesis occurs in a constitutive or light-induced manner, which suggests the diversity of the regulatory mechanism. The mechanism for light-induced carotenoid production in non-phototrophic bacteria has been studied in detail in Myxococcus xanthus, a Gram-negative gliding bacterium. The complicated mechanism involves the activation of an extracytoplasmic function (ECF) sigma factor (CarQ), which leads to the sequestration of a MerR family transcriptional regulator (CarA) that represses the expression of the carotenoid biosynthesis genes in the dark. Recently, we identified another regulatory mechanism for light-induced carotenogenesis in Streptomyces coelicolor A3(2), a Gram-positive soil bacterium. In this organism, the transcription of the carotenoid biosynthesis gene cluster is specified by LitS, a photo-inducible ECF sigma factor. The evidence indicates that the photo-dependent transcription of litS is mediated by LitR, a MerR family transcriptional regulator. In addition, it is suggested that the conformational alteration of LitR upon receiving the illumination signal determines its binding to DNA. The carboxy-terminal domain of LitR contains a possible binding site for Vitamin B12, which may serve as a capturing apparatus for the illumination signal.
Journal of Antibiotics, 2009
Applied Microbiology and Biotechnology, 2007
We obtained carotenoid-producing microorganisms at a high frequency from water samples collected ... more We obtained carotenoid-producing microorganisms at a high frequency from water samples collected at Misasa (Tottori, Japan), a region known for its high natural radioactivity content. A comprehensive 16S rRNA gene-based phylogenetic analysis revealed that the 104 potential carotenoid producers isolated from Misasa could be classified into 38 different species belonging to seven bacterial classes (Flavobacteria, Sphingobacteria, α-Proteobacteria, γ-Proteobacteria, Deinococci, Actinobacteria, and Bacilli). Of these 38 species, 14 showed sequence similarities less than 97% to their closest identified relatives, and 9 were related to genera that have not been described earlier in terms of carotenoid production. The red-pigmented isolates belonging to Deinococci showed marked resistance to γ rays and UV irradiation, while those related to Sphingomonas showed weak resistance. The carotenoids produced by the isolates were zeaxanthin (6 strains), dihydroxyastaxanthin (24 strains), astaxanthin (27 strains), canthaxanthin (10 strains), and unidentified molecular species that were produced by the isolates related to Deinococcus, Exiguobacterium, and Flectobacillus. UV irradiation would be useful for the selective isolation of carotenoid-producing microorganisms, and that new microbial producers and other molecular species of carotenoids may potentially be identified from radioactive environments.