Egon Hansen - Academia.edu (original) (raw)
Papers by Egon Hansen
International Journal of Food Science and Technology, Dec 11, 2021
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Antioxidants
This work studies the emulsifying and antioxidant properties of potato protein hydrolysates (PPHs... more This work studies the emulsifying and antioxidant properties of potato protein hydrolysates (PPHs) fractions obtained through enzymatic hydrolysis of potato protein using trypsin followed by ultrafiltration. Unfractionated (PPH1) and fractionated (PPH2 as >10 kDa, PPH3 as 10–5 kDa, PPH4 as 5–0.8 kDa, and PPH5 as <0.8 kDa) protein hydrolysates were evaluated. Pendant drop tensiometry and dilatational rheology were applied for determining the ability of PPHs to reduce interfacial tension and affect the viscoelasticity of the interfacial films at the oil–water interface. Peptides >10 kDa showed the highest ability to decrease oil–water interfacial tension. All PPH fractions predominantly provided elastic, weak, and easily stretchable interfaces. PPH2 provided a more rigid interfacial layer than the other hydrolysates. Radical scavenging and metal chelating activities of PPHs were also tested and the highest activities were provided by the unfractionated hydrolysate and the fra...
Lactic acid bacteria (LAB) have an extracellular proteolytic system that includes a multi-domain,... more Lactic acid bacteria (LAB) have an extracellular proteolytic system that includes a multi-domain, cell envelope protease (CEP) with a subtilisin homologous protease domain. These CEPs have different proteolytic activities despite having similar protein sequences. Structural characterization has previously been limited to CEP homologs of dairy and human derived LAB strains, excluding CEPs of plant derived LAB strains. CEP structures are a challenge to determine experimentally due to their large size and attachment to the cell envelope. This study aims to clarify the prevalence and structural diversity of CEPs by using the structure prediction software AlphaFold 2. Domain boundaries are clarified based on a comparative analysis of 21 three-dimensional structures, revealing novel domain architectures of CEP homologs that are not necessarily restricted to specific LAB species or ecological niches. The C-terminal flanking region of the protease domain is divided into fibronectin type-III...
Peptides and protein hydrolysates are promising alternatives to substitute chemical additives as ... more Peptides and protein hydrolysates are promising alternatives to substitute chemical additives as functional food ingredients. In this study, we present a novel approach for producing a potato protein hydrolysate with improved emulsifying and foaming properties by data-driven, targeted hydrolysis. Based on previous studies, we selected 15 emulsifier peptides derived from abundant potato proteins, which were clustered based on sequence identity. Through in silico analysis, we determined that from a range of industrial proteases (Neutrase (Neut), Alcalase (Alc), Flavorzyme (Flav) and Trypsin (Tryp)), Tryp was found more likely to release peptides resembling the target peptides. After applying all proteases individually, hydrolysates were assayed for in vitro emulsifying and foaming properties. No direct correlation between degree of hydrolysis and interfacial properties was found. Tryp produced a hydrolysate (DH=5.4%) with the highest (P<0.05) emulsifying and foaming abilities, good...
East African Journal of Sciences, Jun 1, 2017
Camel milk is produced in areas where there is lack of milk cooling facilities coupled with high ... more Camel milk is produced in areas where there is lack of milk cooling facilities coupled with high ambient temperature that exacerbates milk spoilage before it reaches the ultimate market and consumers. To overcome this problem lactoperoxidase system (LPS) is one the methods to preserve freshness of milk until it is marketed or reaches where there is milk cooling facilities. This study was conducted with the objectives of assessing the effect LPS activation on preservation of raw camel and cow milk and to comparing acidification rate of LPS activated camel and cow milk. The effect of LPS activation on inhibition of selected pathogens (i.e. Escherichia coli and Staphylococcus aureus) was also studied. The treatments consisted of a 2 x 4 factorial experiment (LPS activated and non LPS activated with 0, 6, 12, and 24 hrs storage time at 30°C treatments) in a Completely Randomized Design (CRD) with a factorial arrangement and three replications per treatment. Twenty-four camel and cow milk samples obtained from Errer valley ago-pastoralists and Haramaya University Dairy farm, respectively were examined for titratable acidity, total bacterial count (TBC) and coliform count (CC). The result revealed that titratable acidity, CC and TBC in LPS activated milk samples were significantly lower (P< 0.05) than their respective values in non LPS activated milk samples for both cow and camel milk, stored for 6, 12 and 24 hrs. The percent of acidity were not significantly (P>0-05) different than that of the initial acidity level in LPS activated cow and camel milk up to 12hrs of storage. LPS activated milk showed bactericidal effect against TBC and CC both in cow and camel milk. In the current experiment, activation of LPS in camel milk reduced the growth rate of E. coli as compared to non LPS activated milk samples. The bactericidal effect of the LPS suggests that activation of the LPS would be of paramount importance in controlling the growth of microorganisms and improving the microbial quality of both cow and camel milk in the study area. Cow milk with activated LPS showed a slight delay in acidification rate compared to the non LPS activated cow and camel milk using a thermophilic starter culture. From the study, we can suggest that LPS activation of both cow and camel milk helps to extend the shelf life of fresh milk up to 6 and 12 hours, respectively and enables milk producers to sell fresh milk within this time frame and reduce milk wastage. LPS activation can be used in improving the microbiological quality and the shelf-life of raw camel and cow milk where milk cooling facilities are not available. LPS activated milk could also be used for manufacturing of fermented milk products.
Open Journal of Animal Sciences, 2020
This study was conducted to investigate the effect of lactic acid bacteria (LAB) activated lactop... more This study was conducted to investigate the effect of lactic acid bacteria (LAB) activated lactoperoxidase system (LPs) on keeping quality of raw camel milk at room temperature. Camel milk samples were collected from Errer valley, Babile district of eastern Ethiopia. The level of hydrogen peroxide (H 2 O 2) for activation of LPs was optimized using different levels of exogenous H 2 O 2. Strains of LAB (Lactococcus lactis 22333, Weissella confusa 22308, W. confusa 22282, W. confusa 22296, S. Infatarius 22279 and S. lutetiensis 22319) with H 2 O 2 producing properties were evaluated, and W. confusa 22282 was selected as the best strain to produce H 2 O 2. Storage stability of the milk samples was evaluated through the acidification curves, titratable acidity (TA), total bacterial count (TBC) and coliform counts (CC) at storage times of 0, 6, 12, 18, 24 and 48 hours. The LP activity and the inhibitory effect of activated LPs were evaluated by growing E. coli in pasteurized and boiled camel milk samples as contaminating agent. Results indicated that the W. confusa 22282 activated LPs generally showed significantly (P < 0.05) slower rates of acidification, lactic acid production and lower TBC and CC during the storage time compared to the non-activated sample. The H 2 O 2 producing LAB and exogenous H 2 O 2 activated LPs in pasteurized camel milk significantly reduced the growth of E. coli population compared to non-activated pasteurized milk. Overall, the result of acid production and microbial analysis indicated that the activation of LPs by H 2 O 2 producing LAB (i.e. W. confusa 22282) maintained the storage stability of raw camel milk. Therefore, it can be concluded that the activation of LPs by biological method using H 2 O 2 producing LAB can substitute the chemical activation method of LPs in camel milk.
International Dairy Journal, 2020
The present study investigated inhibition of multiple food related pathogens in raw and pasteuris... more The present study investigated inhibition of multiple food related pathogens in raw and pasteurised camel milk during fermentation with four novel Lactococcus lactis strains. All pathogens alone in camel milk reached 8.0 log(CFU mL-1). When the pathogens were cultivated with L. lactis MS22333 or MS22337 they were reduced between 0.9-6.0 log(CFU mL-1). L. lactis MS22314 and MS22336 showed no antimicrobial activity. Bad hygiene and lack of cooling facilities have resulted in spontaneously fermented African camel milk with high incidence of contaminants. Starter cultures promote food safety by controlling the fermentation. Commercial cultures developed for bovine milk acidify poorly in camel milk and cultures optimized for camel milk with inhibitory effects against pathogens are therefore needed. To our knowledge, we have for the first time demonstrated that some L. lactis strains isolated from camel milk can inhibit the growth of food related pathogens in both raw and pasteurised camel milk.
Food Hydrocolloids, 2021
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Frontiers in Bioengineering and Biotechnology, 2020
The cell envelope proteinase (CEP) ofLactococcus lactisis a large extracellular protease covalent... more The cell envelope proteinase (CEP) ofLactococcus lactisis a large extracellular protease covalently linked to the peptidoglycan of the cell wall. Strains ofL. lactisare typically auxotrophic for several amino acids and in order to grow to high cell densities in milk they need an extracellular protease. The structure of the entire CEP enzyme is difficult to determine experimentally due to the large size and due to the attachment to the cell surface. We here describe the use of a combination of structure prediction tools to create a structural model for the entire CEP enzyme ofLactococcus lactis. The model has implications for how the bacterium interacts with casein micelles during growth in milk, and it has implications regarding the energetics of the proteolytic system. Our model for the CEP indicates that the catalytic triad is activated through a structural change caused by interaction with the substrate. The CEP ofL. lactismight become a useful model for the mode of action for en...
Scientific Reports, 2020
Dietary antioxidants are an important preservative in food and have been suggested to help in dis... more Dietary antioxidants are an important preservative in food and have been suggested to help in disease prevention. With consumer demands for less synthetic and safer additives in food products, the food industry is searching for antioxidants that can be marketed as natural. Peptides derived from natural proteins show promise, as they are generally regarded as safe and potentially contain other beneficial bioactivities. Antioxidative peptides are usually obtained by testing various peptides derived from hydrolysis of proteins by a selection of proteases. This slow and cumbersome trial-and-error approach to identify antioxidative peptides has increased interest in developing computational approaches for prediction of antioxidant activity and thereby reduce laboratory work. A few antioxidant predictors exist, however, no tool predicting the antioxidative properties of peptides is, to the best of our knowledge, currently available as a web-server. We here present the AnOxPePred tool and ...
Journal of Bacteriology, 1985
A detailed physical and genetic map of a previously cloned 5.5-kilobase segment of Treponema pall... more A detailed physical and genetic map of a previously cloned 5.5-kilobase segment of Treponema pallidum DNA is described. This segment expressed two proteins that are cell membrane associated in Escherichia coli. The structural genes of these treponemal membrane proteins, tmpA and tmpB, are coordinately expressed, and transcription in E. coli can start from at least two different treponemal promoters. The tmpA and tmpB proteins are the products of in vivo proteolytic cleavage from precursor proteins which are 2 and 4 kilodaltons larger, respectively, than the mature proteins. Because the sizes of the corresponding proteins produced in T. pallidum were identical to those of the mature membrane proteins in E. coli, we concluded that a similar proteolytic processing takes place in both E. coli and T. pallidum. Although tmpA and tmpB were controlled by the same transcription signals, tmpB was expressed to a higher extent than tmpA, and only the tmpB product could be overproduced by placin...
Scientific Reports, 2020
In this work, we developed a novel approach combining bioinformatics, testing of functionality an... more In this work, we developed a novel approach combining bioinformatics, testing of functionality and bottom-up proteomics to obtain peptide emulsifiers from potato side-streams. This is a significant advancement in the process to obtain emulsifier peptides and it is applicable to any type of protein. Our results indicated that structure at the interface is the major determining factor of the emulsifying activity of peptide emulsifiers. Fish oil-in-water emulsions with high physical stability were stabilized with peptides to be predicted to have facial amphiphilicity: (i) peptides with predominantly α-helix conformation at the interface and having 18–29 amino acids, and (ii) peptides with predominantly β-strand conformation at the interface and having 13–15 amino acids. In addition, high physically stable emulsions were obtained with peptides that were predicted to have axial hydrophobic/hydrophilic regions. Peptides containing the sequence FCLKVGV showed high in vitro antioxidant acti...
Applied and Environmental Microbiology, 1993
Two transposition vectors, pTV32 and pLTV1, containing transposon Tn 917 derivatives TV32 and LTV... more Two transposition vectors, pTV32 and pLTV1, containing transposon Tn 917 derivatives TV32 and LTV1, respectively, were introduced into Lactococcus lactis subsp. lactis MG1614. It was found that pTV32 and pLTV1 replicate and that TV32 and LTV1 transpose in this strain. A protocol for production of a collection of Tn 917 insertions in L. lactis subsp. lactis was developed. The physical locations of TV32 on the chromosomal Sma I fragments of 62 independent transpositions were established by pulsed-field gel electrophoresis. These transpositions could be divided into at least 38 different groups that exhibited no Tn 917 -dominating hot spots on the L. lactis subsp. lactis chromosome. A total of 10 of the 62 transpositions resulted in strains that express β-galactosidase. This indicates that there was fusion of the promoterless lacZ of the Tn 917 derivatives to a chromosomal promoter. Thus, the Tn 917 -derived transposons should be powerful genetic tools for studying L. lactis subsp. lac...
Applied and Environmental Microbiology, 1995
Transposon Tn917-LTV1 was used to produce a collection of Lactococcus lactis strains with fusion ... more Transposon Tn917-LTV1 was used to produce a collection of Lactococcus lactis strains with fusion of a promoterless lacZ gene to chromosomal loci. Screening 2,500 Tn917-LTV1 integrants revealed 222 that express beta-galactosidase on plates at 30 degrees C. Pulsed-field gel electrophoresis revealed Tn917-LTV1 insertions in at least 13 loci in 15 strains analyzed. Integrants in which beta-galactosidase expression was regulated by temperature or pH and/or arginine concentration were isolated. In most cases, the regulation observed on plates was reproducible in liquid medium. One integrant, PA170, produces beta-galactosidase at pH 5.2 but not at pH 7.0, produces more beta-galactosidase at 15 degrees C than at 30 degrees C, and has increased beta-galactosidase activity in the stationary phase. DNA fragments potentially carrying promoters from selected Lactococcus lactis integrants were cloned in Escherichia coli. A new promoter probe vector, pAK80, containing promoterless beta-galactosida...
Journal of Dairy Science, 2018
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
LWT, 2018
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
International Dairy Journal, 2018
Protein degradation, rheological properties, sensory properties and the aroma profile of soft bri... more Protein degradation, rheological properties, sensory properties and the aroma profile of soft brined cheese made from camel milk using two levels of coagulant (camel chymosin) [55 and 85 International Milk Clotting Units (IMCU) L-1 ] and two levels of brine (2% or 5% NaCl, w/w) were investigated over a ripening period of 60 d. Casein degradation in soft brined camel milk cheese significantly (p < 0.05) increased during ripening and with increase of coagulant level. Young's modulus and stress at fracture significantly (p < 0.05) increased with increasing level of salt in moisture in the cheese during ripening. However, cheese made with 85 IMCU L-1 coagulant resulted in softening of cheese texture and higher salt uptake. Using descriptive sensory analysis, the experimental cheeses were described as salty, sour and firm. The volatile aroma compounds formed in soft ripened camel milk cheese are affected by ripening time, and coagulant and NaCl levels.
International journal of food science, 2017
A review on the challenges and opportunities of processing camel milk into dairy products is prov... more A review on the challenges and opportunities of processing camel milk into dairy products is provided with an objective of exploring the challenges of processing and assessing the opportunities for developing functional products from camel milk. The gross composition of camel milk is similar to bovine milk. Nonetheless, the relative composition, distribution, and the molecular structure of the milk components are reported to be different. Consequently, manufacturing of camel dairy products such as cheese, yoghurt, or butter using the same technology as for dairy products from bovine milk can result in processing difficulties and products of inferior quality. However, scientific evidence points to the possibility of transforming camel milk into products by optimization of the processing parameters. Additionally, camel milk has traditionally been used for its medicinal values and recent scientific studies confirm that it is a rich source of bioactive, antimicrobial, and antioxidant su...
Journal of Bacteriology, 1996
Two genes, hom and thrB, involved in threonine biosynthesis in Lactococcus lactis MG1614, were cl... more Two genes, hom and thrB, involved in threonine biosynthesis in Lactococcus lactis MG1614, were cloned and sequenced. These genes, which encode homoserine dehydrogenase and homoserine kinase, were initially identified by the homology of their gene products with known homoserine dehydrogenases and homoserine kinases from other organisms. The identification was supported by construction of a mutant containing a deletion in hom and thrB that was unable to grow in a defined medium lacking threonine. Transcriptional analysis showed that the two genes were located in a bicistronic operon with the order 5' hom-thrB 3' and that transcription started 66 bp upstream of the translational start codon of the hom gene. A putative -10 promoter region (TATAAT) was located 6 bp upstream of the transcriptional start point, but no putative -35 region was identified. A DNA fragment covering 155 bp upstream of the hom translational start site was functional in pAK80, an L. lactis promoter probe v...
International Journal of Food Science and Technology, Dec 11, 2021
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Antioxidants
This work studies the emulsifying and antioxidant properties of potato protein hydrolysates (PPHs... more This work studies the emulsifying and antioxidant properties of potato protein hydrolysates (PPHs) fractions obtained through enzymatic hydrolysis of potato protein using trypsin followed by ultrafiltration. Unfractionated (PPH1) and fractionated (PPH2 as >10 kDa, PPH3 as 10–5 kDa, PPH4 as 5–0.8 kDa, and PPH5 as <0.8 kDa) protein hydrolysates were evaluated. Pendant drop tensiometry and dilatational rheology were applied for determining the ability of PPHs to reduce interfacial tension and affect the viscoelasticity of the interfacial films at the oil–water interface. Peptides >10 kDa showed the highest ability to decrease oil–water interfacial tension. All PPH fractions predominantly provided elastic, weak, and easily stretchable interfaces. PPH2 provided a more rigid interfacial layer than the other hydrolysates. Radical scavenging and metal chelating activities of PPHs were also tested and the highest activities were provided by the unfractionated hydrolysate and the fra...
Lactic acid bacteria (LAB) have an extracellular proteolytic system that includes a multi-domain,... more Lactic acid bacteria (LAB) have an extracellular proteolytic system that includes a multi-domain, cell envelope protease (CEP) with a subtilisin homologous protease domain. These CEPs have different proteolytic activities despite having similar protein sequences. Structural characterization has previously been limited to CEP homologs of dairy and human derived LAB strains, excluding CEPs of plant derived LAB strains. CEP structures are a challenge to determine experimentally due to their large size and attachment to the cell envelope. This study aims to clarify the prevalence and structural diversity of CEPs by using the structure prediction software AlphaFold 2. Domain boundaries are clarified based on a comparative analysis of 21 three-dimensional structures, revealing novel domain architectures of CEP homologs that are not necessarily restricted to specific LAB species or ecological niches. The C-terminal flanking region of the protease domain is divided into fibronectin type-III...
Peptides and protein hydrolysates are promising alternatives to substitute chemical additives as ... more Peptides and protein hydrolysates are promising alternatives to substitute chemical additives as functional food ingredients. In this study, we present a novel approach for producing a potato protein hydrolysate with improved emulsifying and foaming properties by data-driven, targeted hydrolysis. Based on previous studies, we selected 15 emulsifier peptides derived from abundant potato proteins, which were clustered based on sequence identity. Through in silico analysis, we determined that from a range of industrial proteases (Neutrase (Neut), Alcalase (Alc), Flavorzyme (Flav) and Trypsin (Tryp)), Tryp was found more likely to release peptides resembling the target peptides. After applying all proteases individually, hydrolysates were assayed for in vitro emulsifying and foaming properties. No direct correlation between degree of hydrolysis and interfacial properties was found. Tryp produced a hydrolysate (DH=5.4%) with the highest (P<0.05) emulsifying and foaming abilities, good...
East African Journal of Sciences, Jun 1, 2017
Camel milk is produced in areas where there is lack of milk cooling facilities coupled with high ... more Camel milk is produced in areas where there is lack of milk cooling facilities coupled with high ambient temperature that exacerbates milk spoilage before it reaches the ultimate market and consumers. To overcome this problem lactoperoxidase system (LPS) is one the methods to preserve freshness of milk until it is marketed or reaches where there is milk cooling facilities. This study was conducted with the objectives of assessing the effect LPS activation on preservation of raw camel and cow milk and to comparing acidification rate of LPS activated camel and cow milk. The effect of LPS activation on inhibition of selected pathogens (i.e. Escherichia coli and Staphylococcus aureus) was also studied. The treatments consisted of a 2 x 4 factorial experiment (LPS activated and non LPS activated with 0, 6, 12, and 24 hrs storage time at 30°C treatments) in a Completely Randomized Design (CRD) with a factorial arrangement and three replications per treatment. Twenty-four camel and cow milk samples obtained from Errer valley ago-pastoralists and Haramaya University Dairy farm, respectively were examined for titratable acidity, total bacterial count (TBC) and coliform count (CC). The result revealed that titratable acidity, CC and TBC in LPS activated milk samples were significantly lower (P< 0.05) than their respective values in non LPS activated milk samples for both cow and camel milk, stored for 6, 12 and 24 hrs. The percent of acidity were not significantly (P>0-05) different than that of the initial acidity level in LPS activated cow and camel milk up to 12hrs of storage. LPS activated milk showed bactericidal effect against TBC and CC both in cow and camel milk. In the current experiment, activation of LPS in camel milk reduced the growth rate of E. coli as compared to non LPS activated milk samples. The bactericidal effect of the LPS suggests that activation of the LPS would be of paramount importance in controlling the growth of microorganisms and improving the microbial quality of both cow and camel milk in the study area. Cow milk with activated LPS showed a slight delay in acidification rate compared to the non LPS activated cow and camel milk using a thermophilic starter culture. From the study, we can suggest that LPS activation of both cow and camel milk helps to extend the shelf life of fresh milk up to 6 and 12 hours, respectively and enables milk producers to sell fresh milk within this time frame and reduce milk wastage. LPS activation can be used in improving the microbiological quality and the shelf-life of raw camel and cow milk where milk cooling facilities are not available. LPS activated milk could also be used for manufacturing of fermented milk products.
Open Journal of Animal Sciences, 2020
This study was conducted to investigate the effect of lactic acid bacteria (LAB) activated lactop... more This study was conducted to investigate the effect of lactic acid bacteria (LAB) activated lactoperoxidase system (LPs) on keeping quality of raw camel milk at room temperature. Camel milk samples were collected from Errer valley, Babile district of eastern Ethiopia. The level of hydrogen peroxide (H 2 O 2) for activation of LPs was optimized using different levels of exogenous H 2 O 2. Strains of LAB (Lactococcus lactis 22333, Weissella confusa 22308, W. confusa 22282, W. confusa 22296, S. Infatarius 22279 and S. lutetiensis 22319) with H 2 O 2 producing properties were evaluated, and W. confusa 22282 was selected as the best strain to produce H 2 O 2. Storage stability of the milk samples was evaluated through the acidification curves, titratable acidity (TA), total bacterial count (TBC) and coliform counts (CC) at storage times of 0, 6, 12, 18, 24 and 48 hours. The LP activity and the inhibitory effect of activated LPs were evaluated by growing E. coli in pasteurized and boiled camel milk samples as contaminating agent. Results indicated that the W. confusa 22282 activated LPs generally showed significantly (P < 0.05) slower rates of acidification, lactic acid production and lower TBC and CC during the storage time compared to the non-activated sample. The H 2 O 2 producing LAB and exogenous H 2 O 2 activated LPs in pasteurized camel milk significantly reduced the growth of E. coli population compared to non-activated pasteurized milk. Overall, the result of acid production and microbial analysis indicated that the activation of LPs by H 2 O 2 producing LAB (i.e. W. confusa 22282) maintained the storage stability of raw camel milk. Therefore, it can be concluded that the activation of LPs by biological method using H 2 O 2 producing LAB can substitute the chemical activation method of LPs in camel milk.
International Dairy Journal, 2020
The present study investigated inhibition of multiple food related pathogens in raw and pasteuris... more The present study investigated inhibition of multiple food related pathogens in raw and pasteurised camel milk during fermentation with four novel Lactococcus lactis strains. All pathogens alone in camel milk reached 8.0 log(CFU mL-1). When the pathogens were cultivated with L. lactis MS22333 or MS22337 they were reduced between 0.9-6.0 log(CFU mL-1). L. lactis MS22314 and MS22336 showed no antimicrobial activity. Bad hygiene and lack of cooling facilities have resulted in spontaneously fermented African camel milk with high incidence of contaminants. Starter cultures promote food safety by controlling the fermentation. Commercial cultures developed for bovine milk acidify poorly in camel milk and cultures optimized for camel milk with inhibitory effects against pathogens are therefore needed. To our knowledge, we have for the first time demonstrated that some L. lactis strains isolated from camel milk can inhibit the growth of food related pathogens in both raw and pasteurised camel milk.
Food Hydrocolloids, 2021
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Frontiers in Bioengineering and Biotechnology, 2020
The cell envelope proteinase (CEP) ofLactococcus lactisis a large extracellular protease covalent... more The cell envelope proteinase (CEP) ofLactococcus lactisis a large extracellular protease covalently linked to the peptidoglycan of the cell wall. Strains ofL. lactisare typically auxotrophic for several amino acids and in order to grow to high cell densities in milk they need an extracellular protease. The structure of the entire CEP enzyme is difficult to determine experimentally due to the large size and due to the attachment to the cell surface. We here describe the use of a combination of structure prediction tools to create a structural model for the entire CEP enzyme ofLactococcus lactis. The model has implications for how the bacterium interacts with casein micelles during growth in milk, and it has implications regarding the energetics of the proteolytic system. Our model for the CEP indicates that the catalytic triad is activated through a structural change caused by interaction with the substrate. The CEP ofL. lactismight become a useful model for the mode of action for en...
Scientific Reports, 2020
Dietary antioxidants are an important preservative in food and have been suggested to help in dis... more Dietary antioxidants are an important preservative in food and have been suggested to help in disease prevention. With consumer demands for less synthetic and safer additives in food products, the food industry is searching for antioxidants that can be marketed as natural. Peptides derived from natural proteins show promise, as they are generally regarded as safe and potentially contain other beneficial bioactivities. Antioxidative peptides are usually obtained by testing various peptides derived from hydrolysis of proteins by a selection of proteases. This slow and cumbersome trial-and-error approach to identify antioxidative peptides has increased interest in developing computational approaches for prediction of antioxidant activity and thereby reduce laboratory work. A few antioxidant predictors exist, however, no tool predicting the antioxidative properties of peptides is, to the best of our knowledge, currently available as a web-server. We here present the AnOxPePred tool and ...
Journal of Bacteriology, 1985
A detailed physical and genetic map of a previously cloned 5.5-kilobase segment of Treponema pall... more A detailed physical and genetic map of a previously cloned 5.5-kilobase segment of Treponema pallidum DNA is described. This segment expressed two proteins that are cell membrane associated in Escherichia coli. The structural genes of these treponemal membrane proteins, tmpA and tmpB, are coordinately expressed, and transcription in E. coli can start from at least two different treponemal promoters. The tmpA and tmpB proteins are the products of in vivo proteolytic cleavage from precursor proteins which are 2 and 4 kilodaltons larger, respectively, than the mature proteins. Because the sizes of the corresponding proteins produced in T. pallidum were identical to those of the mature membrane proteins in E. coli, we concluded that a similar proteolytic processing takes place in both E. coli and T. pallidum. Although tmpA and tmpB were controlled by the same transcription signals, tmpB was expressed to a higher extent than tmpA, and only the tmpB product could be overproduced by placin...
Scientific Reports, 2020
In this work, we developed a novel approach combining bioinformatics, testing of functionality an... more In this work, we developed a novel approach combining bioinformatics, testing of functionality and bottom-up proteomics to obtain peptide emulsifiers from potato side-streams. This is a significant advancement in the process to obtain emulsifier peptides and it is applicable to any type of protein. Our results indicated that structure at the interface is the major determining factor of the emulsifying activity of peptide emulsifiers. Fish oil-in-water emulsions with high physical stability were stabilized with peptides to be predicted to have facial amphiphilicity: (i) peptides with predominantly α-helix conformation at the interface and having 18–29 amino acids, and (ii) peptides with predominantly β-strand conformation at the interface and having 13–15 amino acids. In addition, high physically stable emulsions were obtained with peptides that were predicted to have axial hydrophobic/hydrophilic regions. Peptides containing the sequence FCLKVGV showed high in vitro antioxidant acti...
Applied and Environmental Microbiology, 1993
Two transposition vectors, pTV32 and pLTV1, containing transposon Tn 917 derivatives TV32 and LTV... more Two transposition vectors, pTV32 and pLTV1, containing transposon Tn 917 derivatives TV32 and LTV1, respectively, were introduced into Lactococcus lactis subsp. lactis MG1614. It was found that pTV32 and pLTV1 replicate and that TV32 and LTV1 transpose in this strain. A protocol for production of a collection of Tn 917 insertions in L. lactis subsp. lactis was developed. The physical locations of TV32 on the chromosomal Sma I fragments of 62 independent transpositions were established by pulsed-field gel electrophoresis. These transpositions could be divided into at least 38 different groups that exhibited no Tn 917 -dominating hot spots on the L. lactis subsp. lactis chromosome. A total of 10 of the 62 transpositions resulted in strains that express β-galactosidase. This indicates that there was fusion of the promoterless lacZ of the Tn 917 derivatives to a chromosomal promoter. Thus, the Tn 917 -derived transposons should be powerful genetic tools for studying L. lactis subsp. lac...
Applied and Environmental Microbiology, 1995
Transposon Tn917-LTV1 was used to produce a collection of Lactococcus lactis strains with fusion ... more Transposon Tn917-LTV1 was used to produce a collection of Lactococcus lactis strains with fusion of a promoterless lacZ gene to chromosomal loci. Screening 2,500 Tn917-LTV1 integrants revealed 222 that express beta-galactosidase on plates at 30 degrees C. Pulsed-field gel electrophoresis revealed Tn917-LTV1 insertions in at least 13 loci in 15 strains analyzed. Integrants in which beta-galactosidase expression was regulated by temperature or pH and/or arginine concentration were isolated. In most cases, the regulation observed on plates was reproducible in liquid medium. One integrant, PA170, produces beta-galactosidase at pH 5.2 but not at pH 7.0, produces more beta-galactosidase at 15 degrees C than at 30 degrees C, and has increased beta-galactosidase activity in the stationary phase. DNA fragments potentially carrying promoters from selected Lactococcus lactis integrants were cloned in Escherichia coli. A new promoter probe vector, pAK80, containing promoterless beta-galactosida...
Journal of Dairy Science, 2018
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
LWT, 2018
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
International Dairy Journal, 2018
Protein degradation, rheological properties, sensory properties and the aroma profile of soft bri... more Protein degradation, rheological properties, sensory properties and the aroma profile of soft brined cheese made from camel milk using two levels of coagulant (camel chymosin) [55 and 85 International Milk Clotting Units (IMCU) L-1 ] and two levels of brine (2% or 5% NaCl, w/w) were investigated over a ripening period of 60 d. Casein degradation in soft brined camel milk cheese significantly (p < 0.05) increased during ripening and with increase of coagulant level. Young's modulus and stress at fracture significantly (p < 0.05) increased with increasing level of salt in moisture in the cheese during ripening. However, cheese made with 85 IMCU L-1 coagulant resulted in softening of cheese texture and higher salt uptake. Using descriptive sensory analysis, the experimental cheeses were described as salty, sour and firm. The volatile aroma compounds formed in soft ripened camel milk cheese are affected by ripening time, and coagulant and NaCl levels.
International journal of food science, 2017
A review on the challenges and opportunities of processing camel milk into dairy products is prov... more A review on the challenges and opportunities of processing camel milk into dairy products is provided with an objective of exploring the challenges of processing and assessing the opportunities for developing functional products from camel milk. The gross composition of camel milk is similar to bovine milk. Nonetheless, the relative composition, distribution, and the molecular structure of the milk components are reported to be different. Consequently, manufacturing of camel dairy products such as cheese, yoghurt, or butter using the same technology as for dairy products from bovine milk can result in processing difficulties and products of inferior quality. However, scientific evidence points to the possibility of transforming camel milk into products by optimization of the processing parameters. Additionally, camel milk has traditionally been used for its medicinal values and recent scientific studies confirm that it is a rich source of bioactive, antimicrobial, and antioxidant su...
Journal of Bacteriology, 1996
Two genes, hom and thrB, involved in threonine biosynthesis in Lactococcus lactis MG1614, were cl... more Two genes, hom and thrB, involved in threonine biosynthesis in Lactococcus lactis MG1614, were cloned and sequenced. These genes, which encode homoserine dehydrogenase and homoserine kinase, were initially identified by the homology of their gene products with known homoserine dehydrogenases and homoserine kinases from other organisms. The identification was supported by construction of a mutant containing a deletion in hom and thrB that was unable to grow in a defined medium lacking threonine. Transcriptional analysis showed that the two genes were located in a bicistronic operon with the order 5' hom-thrB 3' and that transcription started 66 bp upstream of the translational start codon of the hom gene. A putative -10 promoter region (TATAAT) was located 6 bp upstream of the transcriptional start point, but no putative -35 region was identified. A DNA fragment covering 155 bp upstream of the hom translational start site was functional in pAK80, an L. lactis promoter probe v...