Angel Angelov | University of Food Technologies - Plovdiv (original) (raw)
Papers by Angel Angelov
World Journal of Microbiology & Biotechnology, 2004
The effects of furfural on the growth of the lactose-utilizing yeast Candida blankii 35 were inve... more The effects of furfural on the growth of the lactose-utilizing yeast Candida blankii 35 were investigated using the method of continuous cultivation under conditions of carbon limitation and at dilution rates of 0.1 and 0.25 h)1. The data obtained at dilution rate 0.1 h)1 and 0.04% furfural showed a decrease in the yield of biomass by 6% and in the RNA content, but the synthesis of cell protein increased with 11.6% compared to the control. Treatment with 0.08% furfural induced significant changes in growth and biosynthesizing ability. A strong inhibitory effect of furfural was observed: the biomass yield decreased by half at 48 h and the culture the reached the control level of protein content. The effect of 0.02% furfural at 0.25 h)1 dilution rate caused a significant reduction of biomass yield (34.4%) and the substrate utilization rate reached values higher by 52.4% at 48 h, but the protein-synthesizing ability of the cells slightly increased. The results showed that a treatment with 0.04 or 0.08% furfural caused significant disturbances of cell functions, the yields of biomass and protein drastically decreased and the culture was washed out. Data showed that the inhibitory effect of furfural on the growth and protein-synthesizing ability of Candida blankii 35 depends on the inhibitor concentration as well as the dilution rate.
MSystems, Oct 31, 2017
We identified the proteins synthesized by Lactobacillus delbrueckii subsp. bulgaricus strain LBB.... more We identified the proteins synthesized by Lactobacillus delbrueckii subsp. bulgaricus strain LBB.B5 in laboratory culture medium (MRS) at 37°C and milk at 37 and 4°C. Cell-associated proteins were measured by gel-free, shotgun proteomics using high-performance liquid chromatography coupled with tandem mass spectrophotometry. A total of 635 proteins were recovered from all cultures, among which 72 proteins were milk associated (unique or significantly more abundant in milk). LBB.B5 responded to milk by increasing the production of proteins required for purine biosynthesis, carbohydrate metabolism (LacZ and ManM), energy metabolism (TpiA, PgK, Eno, SdhA, and GapN), amino acid synthesis (MetE, CysK, LBU0412, and AspC) and transport (GlnM and GlnP), and stress response (Trx, MsrA, MecA, and SmpB). The requirement for purines was confirmed by the significantly improved cell yields of L. delbrueckii subsp. bulgaricus when incubated in milk supplemented with adenine and guanine. The L. delbrueckii subsp. bulgaricus-expressed proteome in milk changed upon incubation at 4°C for 5 days and included increased levels of 17 proteins, several of which confer functions in stress tolerance (AddB, UvrC, RecA, and DnaJ). However, even with the activation of stress responses in either milk or MRS, L. delbrueckii subsp. bulgaricus did not survive passage through the murine digestive tract. These findings inform efforts to understand how L. delbrueckii subsp. bulgaricus is adapted to the dairy environment and its implications for its health-benefiting properties in the human digestive tract. IMPORTANCE Lactobacillus delbrueckii subsp. bulgaricus has a long history of use in yogurt production. Although commonly cocultured with Streptococcus salivarius subsp. thermophilus in milk, fundamental knowledge of the adaptive responses of L. delbrueckii subsp. bulgaricus to the dairy environment and the consequences of those responses on the use of L. delbrueckii subsp. bulgaricus as a probiotic remain to be elucidated. In this study, we identified proteins of L. delbrueckii subsp. bulgaricus LBB.B5 that are synthesized in higher quantities in milk at growth-conducive and non-growth-conductive (refrigeration) temperatures compared to laboratory culture medium and further examined whether those L. delbrueckii subsp. bulgaricus cultures were affected differently in their capacity to survive transit through the murine digestive tract. This work provides novel insight into how a major, food-adapted microbe responds to its primary habitat. Such knowledge can be applied to improve starter culture and yogurt production and to elucidate matrix effects on probiotic performance.
bioRxiv (Cold Spring Harbor Laboratory), Mar 29, 2021
The intraspecific phenotypic and genetic diversity of Lactiplantibacillus plantarum 20 (formerly ... more The intraspecific phenotypic and genetic diversity of Lactiplantibacillus plantarum 20 (formerly Lactobacillus plantarum) was examined for five strains isolated from fermented olives and eight strains from cactus fruit, fermented tomatoes, teff injera, wheat boza, and wheat sourdough starter sources. Carbohydrate utilization and stress tolerance characteristics showed that the olive isolates grew more robustly in galactose and raffinose, showed higher tolerance to 12% v/v EtOH, and exhibited a greater capacity to inhibit an olive spoilage strain of Saccharomyces cerevisiae than L. plantarum from the other plant sources. Certain traits were variable between fermented olive isolates such as the capacity for biofilm formation and survival 27 at pH 2 or 50 °C. By comparison, all L. plantarum from fruit sources grew better at a pH of 3.5 than the strains from fermented grains. Multi-locus sequence typing and genome sequencing 29 indicated that strains from the same source type tended to be genetically related. Comparative genomics was unable to resolve strain differences, with the exception of the most phenotypically impaired and robust isolates. The findings show that L. plantarum is adapted for growth on specific plants or plant food types, but that intraspecific variation may be important for 33 ecological fitness of L. plantarum within individual habitats. .
Microorganisms, Jun 22, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Food Technology and Biotechnology
Research background. Sourdough is a spontaneously formed, complex microbial ecosystem of various ... more Research background. Sourdough is a spontaneously formed, complex microbial ecosystem of various lactic acid bacteria (LAB) and yeast which, by producing specific metabolites, determines the quality of the baked products. In order to design and control the sourdough with preferred nutritional characteristics, it is crucial that the LAB diversity ofthe product of interest be elucidated. Experimental approach. Using the opportunities of next-generation sequencing (NGS) of the V1–V3 hypervariable gene region of 16S rRNA, we studied the microbial ecosystem of a whole grain sourdough made of Triticum monococcum, originating from Southwestern Bulgaria. Since the DNA extraction method is considered crucial for the accuracy of the sequencing results, as it can introduce significant differences in the examined microbiota, we used three different commercial kits for DNA isolation and analyzed their impact on the observed bacterial diversity. Results and conclusions. All three DNA extraction k...
BIO Web of Conferences
Fermented plant-based foods, including sauerkraut, offer high nutritional and functional value. T... more Fermented plant-based foods, including sauerkraut, offer high nutritional and functional value. Their microflora is dominated by lactic acid bacteria which are a source of different substances with health- promoting benefits and diverse applications in the food industry. Production of exopolysaccharides (EPSs) by lactic acid bacteria attracts particular interest in the food industry due to their rheological properties. In the present study, we isolated 20 strains of lactic acid bacteria from traditional Bulgarian sauerkraut. The isolates were identified by 16S rDNA sequencing and were attributed to Lactiplantibacillus plantarum (75%) and Pediococcus pentosaceus (25%). All strains were screened for their ability to synthesize exopolysaccharides, and 6 of them proved positive. Since culture media composition and especially the carbon source is a critical factor influencing the yield of bacterial EPSs, the impact of various carbon sources on the EPSs synthesis by the selected producers...
BIO Web of Conferences
Food adulteration regarding species origin of meats is a common problem in the meat products sect... more Food adulteration regarding species origin of meats is a common problem in the meat products sector. With regard to horse meat, its undeclared use in food products is not only a fraud, but could present a health risk since is often associated with the presence of the veterinary drug phenylbutazone in meat products. Therefore, it is important to use reliable methods for authentication of meat products regarding their species composition, which are applicable to complex food matrices. Polymerase chain reaction (PCR) with species-specific primers remains the most widely used analytical approach to detect species-related food adulteration due to its high sensitivity and specificity. The aim of the present study was to establish the authenticity of 20 different meat products on the Bulgarian market without declared horse meat content by using a species-specific PCR method. The specificity test of the PCR method used showed no amplification of DNA from beef and pork. A detection limit of ...
Journal of Food Nutrition and Population Health, May 18, 2018
Agriculture and Food, 2015
Through the use of the immunoaffinity clean-up procedure for extraction of ochratoxin A by high i... more Through the use of the immunoaffinity clean-up procedure for extraction of ochratoxin A by high immunoaffinity columns by means of the analytical methodology known as HPLC-FD we have analyzed the quantity of ochratoxin A in 22 must and wine samples during alcoholic fermentation process. Analysis of the samples was done in the University of Food Technologies, Plovdiv – Bulgaria.OTA quantities in all analyzed samples have been under the level allowed by EU for ochratoxin A i.e. 2 ng/ml and as such these wines after consuming do not pose a risk in the future to human health.
In this study work we have determined the quantity of ochratoxin A (OTA) in 54 samples of bottled... more In this study work we have determined the quantity of ochratoxin A (OTA) in 54 samples of bottled wine. The methodology which we used is the method known as High Performance Liquid Chromatography with Fluorescence Detection (HPLC). Before the HPLC analysis we have done the ochratoxin A extraction through the immunoaffinity clean-up procedure by high immunoaffinity columns. Samples that are analyzed have been taken in Kosovo and are wine samples produced and bottled in Republic of Kosovo and the wine samples produced, bottled and imported in Kosovo from other Balkan and Europian Union (EU) countries and beyond. The aim of this research has been the analysis of ochratoxin A in bottled wine for the first time in Kosovo and determination of the risk or not by consumption of the analyzed wines by consumers. The results of all analyzed samples have been below the limit allowed by the EU for ochratoxin A i.e. 2 ng/ml and as such in the future do not pose a risk to human health.
Agriculture and Food, 2015
For quantitative analysis of ochratoxin A in must we have used the analytical method known as HPL... more For quantitative analysis of ochratoxin A in must we have used the analytical method known as HPLC-FD and previously used the immunoaffinity clean-up procedure for extraction of ochratoxin A by high immunoaffinity columns. We have determined the quantity of OTA in 30 must samples. Samples that are analyzed have been taken in the vineyards of Kosovo, concretely in southern part of Kosovo, in Rahoveci and Suhareka region. The results of all analyzed samples have been below the limit allowed by EU for ochratoxin A i.e. 2 ng/ml and as such in the future do not pose a risk to human health. The must grape represents the grape juice from which by means of certain technological processes, in particular alcoholic fermentation process created wine booze. A quantitative determination of ochratoxin A in must is very important to have in early stage of the technological process of winemaking an overview regarding the presence or not of substances dangerous to human health as is in this case the ...
Microbial Biotechnology, 2021
Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a lactic acid bacteria specie... more Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a lactic acid bacteria species found on plants that is essential for many plant food fermentations. In this study, we investigated the intraspecific phenotypic and genetic diversity of 13 L. plantarum strains isolated from different plant foods, including fermented olives and tomatoes, cactus fruit, teff injera, wheat boza and wheat sourdough starter. We found that strains from the same or similar plant food types frequently exhibited similar carbohydrate metabolism and stress tolerance responses. The isolates from acidic, brine-containing ferments (olives and tomatoes) were more resistant to MRS adjusted to pH 3.5 or containing 4% w/v NaCl, than those recovered from grain fermentations. Strains from fermented olives grew robustly on raffinose as the sole carbon source and were better able to grow in the presence of ethanol (8% v/v or sequential exposure of 8% (v/v) and then 12% (v/v) ethanol) than most isolates from other plant types and the reference strain NCIMB8826R. Cell free culture supernatants from the olive-associated strains were also more effective at inhibiting growth of an olive spoilage strain of Saccharomyces cerevisiae. Multi-locus sequence typing and comparative genomics indicated that isolates from the same source tended to be genetically related. However, despite these similarities, other traits were highly variable between strains from the same plant source, including the capacity for biofilm formation and survival at pH 2 or 50°C. Genomic comparisons were unable to resolve strain differences, with the exception of the most phenotypically impaired and robust isolates, highlighting the importance of utilizing phenotypic studies to investigate differences between strains of L. plantarum. The findings show that L. plantarum is adapted for growth on specific plants or plant food types, but that intraspecific variation may be important for ecological fitness and strain coexistence within individual habitats.
Microorganisms
Sourdoughs (SDs) are spontaneously formed microbial ecosystems composed of various species of lac... more Sourdoughs (SDs) are spontaneously formed microbial ecosystems composed of various species of lactic acid bacteria (LAB) and acid-tolerant yeasts in food matrices of cereal flours mixed with water. To date, more than 90 LAB species have been isolated, significantly impacting the organoleptic characteristics, shelf life, and health properties of bakery products. To learn more about the unique bacterial communities involved in creating regional Bulgarian sourdoughs, we examined the metacommunities of five sourdoughs produced by spontaneous fermentation and maintained by backslopping in bakeries from three geographic locations. The 16S rRNA gene amplicon sequencing showed that the former genus Lactobacillus was predominant in the studied sourdoughs (51.0–78.9%). Weissella (0.9–42.8%), Herbaspirillum (1.6–3.8%), Serratia (0.1–11.7%), Pediococcus (0.2–7.5%), Bacteroides (0.1–1.3%), and Sphingomonas (0.1–0.5%) were also found in all 5 samples. Genera Leuconostoc, Enterococcus, Bacillus, a...
Foods
Exopolysaccharides (EPSs) produced by lactic acid bacteria present a particular interest for the ... more Exopolysaccharides (EPSs) produced by lactic acid bacteria present a particular interest for the food industry since they can be incorporated in foods via in situ production by selected starter cultures or applied as natural additives to improve the quality of various food products. In the present study, 43 strains were isolated from different plant-based fermented foods and identified by molecular methods. The species found were distinctively specific according to the food source. Only six Lactiplantibacillus plantarum strains, all isolated from sauerkraut, showed the ability to produce exopolysaccharide (EPS). The utilization of glucose, fructose and sucrose was explored with regard to EPS and biomass accumulation by the tested strains. Sucrose was clearly the best carbon source for EPS production by most of the strains, yielding up to 211.53 mg/L by strain Lactiplantibacillus plantarum ZE2, while biomass accumulation reached the highest levels in the glucose-based culture medium....
Chemical Engineering & Technology, Jul 1, 2009
A promising new dimension in the field of biotechnology is the use of microorganisms for the prod... more A promising new dimension in the field of biotechnology is the use of microorganisms for the production of inorganic nanoscale particles. The interest in nanotechnology is provoked by the unique properties of nanostructured materials and their potential fields of application ranging from medicine to electronics. This review article presents a systematic overview of the microorganisms capable of producing nanoparticles, and describes cellular mechanisms and outlines cultivation conditions that turn this process into a successful synthetic pathway.
Italian Journal of Food Science
The present study aimed to obtain good quality croissants from wholegrain wheat flour using bakin... more The present study aimed to obtain good quality croissants from wholegrain wheat flour using baking sourdoughs prepared from single starter cultures of Pediococcus acidilactici 02P108 (PA), Pediococcus pentosaceus SM2D17 (PP) and Enteroccocus durans 09B374 (ED) as an attempt to overcome the usual negative effects of the wholegrain flour on the characteristics of this specific bakery product group. Results showed that the addition of sourdough in the wholegrain wheat dough had similar performance as that of conventional baker’s yeast regarding the rheological characteristics of dough. The dynamic viscosity of all sourdough-leavened samples remained higher than that of the control sample at all tested shear rates. A positive effect of sourdoughs used on the development of baking dough was observed in terms of specific volume improvement, higher degree of softening, and reduced baking loss. However, these positive effects were found as strain-specific. The use of Enteroccocus durans 09B...
Journal of the Science of Food and Agriculture, 2005
Fermentation of a prebiotic containing oat substrate with probiotic lactic acid bacteria and yeas... more Fermentation of a prebiotic containing oat substrate with probiotic lactic acid bacteria and yeast strains is an intriguing approach for the development of new synbiotic functional products. This approach was applied in the present work by using pure and mixed microbial cultures to ferment a heat-treated oat mash. Results show that the strains studied were appropriate for oat fermentation and the process could be completed for 6-10 h depending on the strain. The viable cell counts achieved within this time were above the required levels of 10 6 -10 7 cfu ml −1 for probiotic products. Both single lactic acid bacteria strains and mixed cultures of the same strains with yeast were found suitable for oat fermentation. However, the pure LAB cultures attributed better flavour and shelf life of the oat drinks. The content of the prebiotic oat component beta-glucan remained within 0.30-0.36% during fermentation and storage of the drinks obtained with each of the strains used. Thus, these products would contribute diet with the valuable functional properties of beta-glucan. Also, the viability of pure and mixed cultures in the oat products was good: levels of cell counts remained above the required numbers for probiotic products throughout the estimated shelf-life period.
Journal of Industrial Microbiology & Biotechnology, 2002
In an investigation of the changes in the microflora along the pathway: kefir grains (A)-->... more In an investigation of the changes in the microflora along the pathway: kefir grains (A)-->kefir made from kefir grains (B)-->kefir made from kefir as inoculum (C), the following species of lactic acid bacteria (83-90%) of the microbial count in the grains) were identified: Lactococcus lactis subsp. lactis, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus, Lactobacillus casei subsp. pseudoplantarum and Lactobacillus brevis. Yeasts (10-17%) identified were Kluyveromyces marxianus var. lactis, Saccharomyces cerevisiae, Candida inconspicua and Candida maris. In the microbial population of kefir grains and kefir made from them the homofermentative lactic streptococci (52-65% and 79-86%, respectively) predominated. Within the group of lactobacilli, the homofermentative thermophilic species L. delbrueckii subsp. bulgaricus and L. helveticus (70-87% of the isolated bacilli) predominated. Along the pathway A-->B-->C, the streptococcal proportion in the total kefir microflora increased by 26-30% whereas the lactobacilli decreased by 13-23%. K. marxianus var. lactis was permanently present in kefir grains and kefirs, whereas the dominant lactose-negative yeast in the total yeast flora of the kefir grains dramatically decreased in kefir C.
Journal of Food Science and Technology, 2011
Probiotics are the microorganisms that impart therapeutic effect and promote health by preventing... more Probiotics are the microorganisms that impart therapeutic effect and promote health by preventing various diseases. In the present work, the volatile compounds were studied in the native isolate Lactobacillus plantarum (LP) and after adaptation to resist gastro intestinal tract (GIT) conditions, which was coded as LPcfr. A number of therapeutically important compounds were present in LPcfr like butanediol (2.5%) and propionic acid (2.8%), which were not found in LP. Hexadecane (3%), butanoic acid (2%), dodecanal (2%), hexanal (7.5%), hexadecanoic acid (4%) and heptanal (6%) were found in higher concentrations in LPcfr as compared to the parent strain LP. Production of oleic acid (LP-19.2%; LPcfr -33.5%), known for reducing blood cholesterol and linoleic acid (LPcfr 2.3%), and a conjugated fatty acid known as a novel beneficial functional lipid was noticed. Linoleic acid was absent in LP. These important fatty acids were found in larger quantities in the probiotic adapted culture strain LPcfr as compared to the parent strain LP.
World Journal of Microbiology & Biotechnology, 2004
The effects of furfural on the growth of the lactose-utilizing yeast Candida blankii 35 were inve... more The effects of furfural on the growth of the lactose-utilizing yeast Candida blankii 35 were investigated using the method of continuous cultivation under conditions of carbon limitation and at dilution rates of 0.1 and 0.25 h)1. The data obtained at dilution rate 0.1 h)1 and 0.04% furfural showed a decrease in the yield of biomass by 6% and in the RNA content, but the synthesis of cell protein increased with 11.6% compared to the control. Treatment with 0.08% furfural induced significant changes in growth and biosynthesizing ability. A strong inhibitory effect of furfural was observed: the biomass yield decreased by half at 48 h and the culture the reached the control level of protein content. The effect of 0.02% furfural at 0.25 h)1 dilution rate caused a significant reduction of biomass yield (34.4%) and the substrate utilization rate reached values higher by 52.4% at 48 h, but the protein-synthesizing ability of the cells slightly increased. The results showed that a treatment with 0.04 or 0.08% furfural caused significant disturbances of cell functions, the yields of biomass and protein drastically decreased and the culture was washed out. Data showed that the inhibitory effect of furfural on the growth and protein-synthesizing ability of Candida blankii 35 depends on the inhibitor concentration as well as the dilution rate.
MSystems, Oct 31, 2017
We identified the proteins synthesized by Lactobacillus delbrueckii subsp. bulgaricus strain LBB.... more We identified the proteins synthesized by Lactobacillus delbrueckii subsp. bulgaricus strain LBB.B5 in laboratory culture medium (MRS) at 37°C and milk at 37 and 4°C. Cell-associated proteins were measured by gel-free, shotgun proteomics using high-performance liquid chromatography coupled with tandem mass spectrophotometry. A total of 635 proteins were recovered from all cultures, among which 72 proteins were milk associated (unique or significantly more abundant in milk). LBB.B5 responded to milk by increasing the production of proteins required for purine biosynthesis, carbohydrate metabolism (LacZ and ManM), energy metabolism (TpiA, PgK, Eno, SdhA, and GapN), amino acid synthesis (MetE, CysK, LBU0412, and AspC) and transport (GlnM and GlnP), and stress response (Trx, MsrA, MecA, and SmpB). The requirement for purines was confirmed by the significantly improved cell yields of L. delbrueckii subsp. bulgaricus when incubated in milk supplemented with adenine and guanine. The L. delbrueckii subsp. bulgaricus-expressed proteome in milk changed upon incubation at 4°C for 5 days and included increased levels of 17 proteins, several of which confer functions in stress tolerance (AddB, UvrC, RecA, and DnaJ). However, even with the activation of stress responses in either milk or MRS, L. delbrueckii subsp. bulgaricus did not survive passage through the murine digestive tract. These findings inform efforts to understand how L. delbrueckii subsp. bulgaricus is adapted to the dairy environment and its implications for its health-benefiting properties in the human digestive tract. IMPORTANCE Lactobacillus delbrueckii subsp. bulgaricus has a long history of use in yogurt production. Although commonly cocultured with Streptococcus salivarius subsp. thermophilus in milk, fundamental knowledge of the adaptive responses of L. delbrueckii subsp. bulgaricus to the dairy environment and the consequences of those responses on the use of L. delbrueckii subsp. bulgaricus as a probiotic remain to be elucidated. In this study, we identified proteins of L. delbrueckii subsp. bulgaricus LBB.B5 that are synthesized in higher quantities in milk at growth-conducive and non-growth-conductive (refrigeration) temperatures compared to laboratory culture medium and further examined whether those L. delbrueckii subsp. bulgaricus cultures were affected differently in their capacity to survive transit through the murine digestive tract. This work provides novel insight into how a major, food-adapted microbe responds to its primary habitat. Such knowledge can be applied to improve starter culture and yogurt production and to elucidate matrix effects on probiotic performance.
bioRxiv (Cold Spring Harbor Laboratory), Mar 29, 2021
The intraspecific phenotypic and genetic diversity of Lactiplantibacillus plantarum 20 (formerly ... more The intraspecific phenotypic and genetic diversity of Lactiplantibacillus plantarum 20 (formerly Lactobacillus plantarum) was examined for five strains isolated from fermented olives and eight strains from cactus fruit, fermented tomatoes, teff injera, wheat boza, and wheat sourdough starter sources. Carbohydrate utilization and stress tolerance characteristics showed that the olive isolates grew more robustly in galactose and raffinose, showed higher tolerance to 12% v/v EtOH, and exhibited a greater capacity to inhibit an olive spoilage strain of Saccharomyces cerevisiae than L. plantarum from the other plant sources. Certain traits were variable between fermented olive isolates such as the capacity for biofilm formation and survival 27 at pH 2 or 50 °C. By comparison, all L. plantarum from fruit sources grew better at a pH of 3.5 than the strains from fermented grains. Multi-locus sequence typing and genome sequencing 29 indicated that strains from the same source type tended to be genetically related. Comparative genomics was unable to resolve strain differences, with the exception of the most phenotypically impaired and robust isolates. The findings show that L. plantarum is adapted for growth on specific plants or plant food types, but that intraspecific variation may be important for 33 ecological fitness of L. plantarum within individual habitats. .
Microorganisms, Jun 22, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Food Technology and Biotechnology
Research background. Sourdough is a spontaneously formed, complex microbial ecosystem of various ... more Research background. Sourdough is a spontaneously formed, complex microbial ecosystem of various lactic acid bacteria (LAB) and yeast which, by producing specific metabolites, determines the quality of the baked products. In order to design and control the sourdough with preferred nutritional characteristics, it is crucial that the LAB diversity ofthe product of interest be elucidated. Experimental approach. Using the opportunities of next-generation sequencing (NGS) of the V1–V3 hypervariable gene region of 16S rRNA, we studied the microbial ecosystem of a whole grain sourdough made of Triticum monococcum, originating from Southwestern Bulgaria. Since the DNA extraction method is considered crucial for the accuracy of the sequencing results, as it can introduce significant differences in the examined microbiota, we used three different commercial kits for DNA isolation and analyzed their impact on the observed bacterial diversity. Results and conclusions. All three DNA extraction k...
BIO Web of Conferences
Fermented plant-based foods, including sauerkraut, offer high nutritional and functional value. T... more Fermented plant-based foods, including sauerkraut, offer high nutritional and functional value. Their microflora is dominated by lactic acid bacteria which are a source of different substances with health- promoting benefits and diverse applications in the food industry. Production of exopolysaccharides (EPSs) by lactic acid bacteria attracts particular interest in the food industry due to their rheological properties. In the present study, we isolated 20 strains of lactic acid bacteria from traditional Bulgarian sauerkraut. The isolates were identified by 16S rDNA sequencing and were attributed to Lactiplantibacillus plantarum (75%) and Pediococcus pentosaceus (25%). All strains were screened for their ability to synthesize exopolysaccharides, and 6 of them proved positive. Since culture media composition and especially the carbon source is a critical factor influencing the yield of bacterial EPSs, the impact of various carbon sources on the EPSs synthesis by the selected producers...
BIO Web of Conferences
Food adulteration regarding species origin of meats is a common problem in the meat products sect... more Food adulteration regarding species origin of meats is a common problem in the meat products sector. With regard to horse meat, its undeclared use in food products is not only a fraud, but could present a health risk since is often associated with the presence of the veterinary drug phenylbutazone in meat products. Therefore, it is important to use reliable methods for authentication of meat products regarding their species composition, which are applicable to complex food matrices. Polymerase chain reaction (PCR) with species-specific primers remains the most widely used analytical approach to detect species-related food adulteration due to its high sensitivity and specificity. The aim of the present study was to establish the authenticity of 20 different meat products on the Bulgarian market without declared horse meat content by using a species-specific PCR method. The specificity test of the PCR method used showed no amplification of DNA from beef and pork. A detection limit of ...
Journal of Food Nutrition and Population Health, May 18, 2018
Agriculture and Food, 2015
Through the use of the immunoaffinity clean-up procedure for extraction of ochratoxin A by high i... more Through the use of the immunoaffinity clean-up procedure for extraction of ochratoxin A by high immunoaffinity columns by means of the analytical methodology known as HPLC-FD we have analyzed the quantity of ochratoxin A in 22 must and wine samples during alcoholic fermentation process. Analysis of the samples was done in the University of Food Technologies, Plovdiv – Bulgaria.OTA quantities in all analyzed samples have been under the level allowed by EU for ochratoxin A i.e. 2 ng/ml and as such these wines after consuming do not pose a risk in the future to human health.
In this study work we have determined the quantity of ochratoxin A (OTA) in 54 samples of bottled... more In this study work we have determined the quantity of ochratoxin A (OTA) in 54 samples of bottled wine. The methodology which we used is the method known as High Performance Liquid Chromatography with Fluorescence Detection (HPLC). Before the HPLC analysis we have done the ochratoxin A extraction through the immunoaffinity clean-up procedure by high immunoaffinity columns. Samples that are analyzed have been taken in Kosovo and are wine samples produced and bottled in Republic of Kosovo and the wine samples produced, bottled and imported in Kosovo from other Balkan and Europian Union (EU) countries and beyond. The aim of this research has been the analysis of ochratoxin A in bottled wine for the first time in Kosovo and determination of the risk or not by consumption of the analyzed wines by consumers. The results of all analyzed samples have been below the limit allowed by the EU for ochratoxin A i.e. 2 ng/ml and as such in the future do not pose a risk to human health.
Agriculture and Food, 2015
For quantitative analysis of ochratoxin A in must we have used the analytical method known as HPL... more For quantitative analysis of ochratoxin A in must we have used the analytical method known as HPLC-FD and previously used the immunoaffinity clean-up procedure for extraction of ochratoxin A by high immunoaffinity columns. We have determined the quantity of OTA in 30 must samples. Samples that are analyzed have been taken in the vineyards of Kosovo, concretely in southern part of Kosovo, in Rahoveci and Suhareka region. The results of all analyzed samples have been below the limit allowed by EU for ochratoxin A i.e. 2 ng/ml and as such in the future do not pose a risk to human health. The must grape represents the grape juice from which by means of certain technological processes, in particular alcoholic fermentation process created wine booze. A quantitative determination of ochratoxin A in must is very important to have in early stage of the technological process of winemaking an overview regarding the presence or not of substances dangerous to human health as is in this case the ...
Microbial Biotechnology, 2021
Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a lactic acid bacteria specie... more Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a lactic acid bacteria species found on plants that is essential for many plant food fermentations. In this study, we investigated the intraspecific phenotypic and genetic diversity of 13 L. plantarum strains isolated from different plant foods, including fermented olives and tomatoes, cactus fruit, teff injera, wheat boza and wheat sourdough starter. We found that strains from the same or similar plant food types frequently exhibited similar carbohydrate metabolism and stress tolerance responses. The isolates from acidic, brine-containing ferments (olives and tomatoes) were more resistant to MRS adjusted to pH 3.5 or containing 4% w/v NaCl, than those recovered from grain fermentations. Strains from fermented olives grew robustly on raffinose as the sole carbon source and were better able to grow in the presence of ethanol (8% v/v or sequential exposure of 8% (v/v) and then 12% (v/v) ethanol) than most isolates from other plant types and the reference strain NCIMB8826R. Cell free culture supernatants from the olive-associated strains were also more effective at inhibiting growth of an olive spoilage strain of Saccharomyces cerevisiae. Multi-locus sequence typing and comparative genomics indicated that isolates from the same source tended to be genetically related. However, despite these similarities, other traits were highly variable between strains from the same plant source, including the capacity for biofilm formation and survival at pH 2 or 50°C. Genomic comparisons were unable to resolve strain differences, with the exception of the most phenotypically impaired and robust isolates, highlighting the importance of utilizing phenotypic studies to investigate differences between strains of L. plantarum. The findings show that L. plantarum is adapted for growth on specific plants or plant food types, but that intraspecific variation may be important for ecological fitness and strain coexistence within individual habitats.
Microorganisms
Sourdoughs (SDs) are spontaneously formed microbial ecosystems composed of various species of lac... more Sourdoughs (SDs) are spontaneously formed microbial ecosystems composed of various species of lactic acid bacteria (LAB) and acid-tolerant yeasts in food matrices of cereal flours mixed with water. To date, more than 90 LAB species have been isolated, significantly impacting the organoleptic characteristics, shelf life, and health properties of bakery products. To learn more about the unique bacterial communities involved in creating regional Bulgarian sourdoughs, we examined the metacommunities of five sourdoughs produced by spontaneous fermentation and maintained by backslopping in bakeries from three geographic locations. The 16S rRNA gene amplicon sequencing showed that the former genus Lactobacillus was predominant in the studied sourdoughs (51.0–78.9%). Weissella (0.9–42.8%), Herbaspirillum (1.6–3.8%), Serratia (0.1–11.7%), Pediococcus (0.2–7.5%), Bacteroides (0.1–1.3%), and Sphingomonas (0.1–0.5%) were also found in all 5 samples. Genera Leuconostoc, Enterococcus, Bacillus, a...
Foods
Exopolysaccharides (EPSs) produced by lactic acid bacteria present a particular interest for the ... more Exopolysaccharides (EPSs) produced by lactic acid bacteria present a particular interest for the food industry since they can be incorporated in foods via in situ production by selected starter cultures or applied as natural additives to improve the quality of various food products. In the present study, 43 strains were isolated from different plant-based fermented foods and identified by molecular methods. The species found were distinctively specific according to the food source. Only six Lactiplantibacillus plantarum strains, all isolated from sauerkraut, showed the ability to produce exopolysaccharide (EPS). The utilization of glucose, fructose and sucrose was explored with regard to EPS and biomass accumulation by the tested strains. Sucrose was clearly the best carbon source for EPS production by most of the strains, yielding up to 211.53 mg/L by strain Lactiplantibacillus plantarum ZE2, while biomass accumulation reached the highest levels in the glucose-based culture medium....
Chemical Engineering & Technology, Jul 1, 2009
A promising new dimension in the field of biotechnology is the use of microorganisms for the prod... more A promising new dimension in the field of biotechnology is the use of microorganisms for the production of inorganic nanoscale particles. The interest in nanotechnology is provoked by the unique properties of nanostructured materials and their potential fields of application ranging from medicine to electronics. This review article presents a systematic overview of the microorganisms capable of producing nanoparticles, and describes cellular mechanisms and outlines cultivation conditions that turn this process into a successful synthetic pathway.
Italian Journal of Food Science
The present study aimed to obtain good quality croissants from wholegrain wheat flour using bakin... more The present study aimed to obtain good quality croissants from wholegrain wheat flour using baking sourdoughs prepared from single starter cultures of Pediococcus acidilactici 02P108 (PA), Pediococcus pentosaceus SM2D17 (PP) and Enteroccocus durans 09B374 (ED) as an attempt to overcome the usual negative effects of the wholegrain flour on the characteristics of this specific bakery product group. Results showed that the addition of sourdough in the wholegrain wheat dough had similar performance as that of conventional baker’s yeast regarding the rheological characteristics of dough. The dynamic viscosity of all sourdough-leavened samples remained higher than that of the control sample at all tested shear rates. A positive effect of sourdoughs used on the development of baking dough was observed in terms of specific volume improvement, higher degree of softening, and reduced baking loss. However, these positive effects were found as strain-specific. The use of Enteroccocus durans 09B...
Journal of the Science of Food and Agriculture, 2005
Fermentation of a prebiotic containing oat substrate with probiotic lactic acid bacteria and yeas... more Fermentation of a prebiotic containing oat substrate with probiotic lactic acid bacteria and yeast strains is an intriguing approach for the development of new synbiotic functional products. This approach was applied in the present work by using pure and mixed microbial cultures to ferment a heat-treated oat mash. Results show that the strains studied were appropriate for oat fermentation and the process could be completed for 6-10 h depending on the strain. The viable cell counts achieved within this time were above the required levels of 10 6 -10 7 cfu ml −1 for probiotic products. Both single lactic acid bacteria strains and mixed cultures of the same strains with yeast were found suitable for oat fermentation. However, the pure LAB cultures attributed better flavour and shelf life of the oat drinks. The content of the prebiotic oat component beta-glucan remained within 0.30-0.36% during fermentation and storage of the drinks obtained with each of the strains used. Thus, these products would contribute diet with the valuable functional properties of beta-glucan. Also, the viability of pure and mixed cultures in the oat products was good: levels of cell counts remained above the required numbers for probiotic products throughout the estimated shelf-life period.
Journal of Industrial Microbiology & Biotechnology, 2002
In an investigation of the changes in the microflora along the pathway: kefir grains (A)-->... more In an investigation of the changes in the microflora along the pathway: kefir grains (A)-->kefir made from kefir grains (B)-->kefir made from kefir as inoculum (C), the following species of lactic acid bacteria (83-90%) of the microbial count in the grains) were identified: Lactococcus lactis subsp. lactis, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus, Lactobacillus casei subsp. pseudoplantarum and Lactobacillus brevis. Yeasts (10-17%) identified were Kluyveromyces marxianus var. lactis, Saccharomyces cerevisiae, Candida inconspicua and Candida maris. In the microbial population of kefir grains and kefir made from them the homofermentative lactic streptococci (52-65% and 79-86%, respectively) predominated. Within the group of lactobacilli, the homofermentative thermophilic species L. delbrueckii subsp. bulgaricus and L. helveticus (70-87% of the isolated bacilli) predominated. Along the pathway A-->B-->C, the streptococcal proportion in the total kefir microflora increased by 26-30% whereas the lactobacilli decreased by 13-23%. K. marxianus var. lactis was permanently present in kefir grains and kefirs, whereas the dominant lactose-negative yeast in the total yeast flora of the kefir grains dramatically decreased in kefir C.
Journal of Food Science and Technology, 2011
Probiotics are the microorganisms that impart therapeutic effect and promote health by preventing... more Probiotics are the microorganisms that impart therapeutic effect and promote health by preventing various diseases. In the present work, the volatile compounds were studied in the native isolate Lactobacillus plantarum (LP) and after adaptation to resist gastro intestinal tract (GIT) conditions, which was coded as LPcfr. A number of therapeutically important compounds were present in LPcfr like butanediol (2.5%) and propionic acid (2.8%), which were not found in LP. Hexadecane (3%), butanoic acid (2%), dodecanal (2%), hexanal (7.5%), hexadecanoic acid (4%) and heptanal (6%) were found in higher concentrations in LPcfr as compared to the parent strain LP. Production of oleic acid (LP-19.2%; LPcfr -33.5%), known for reducing blood cholesterol and linoleic acid (LPcfr 2.3%), and a conjugated fatty acid known as a novel beneficial functional lipid was noticed. Linoleic acid was absent in LP. These important fatty acids were found in larger quantities in the probiotic adapted culture strain LPcfr as compared to the parent strain LP.