Starter Cultures For Production Research Articles

Evaluation of stress tolerance and design of alternative culture media for the production of fermentation starter cultures in cacao

Ecuador is one of the world's leading producers of cacao beans, and Nacional x Trinitario cacao represents one of the most distinctive varieties due to its flavor and aroma characteristics. This study aimed to evaluate the effect of the starter culture isolated from microbial diversity during the spontaneous fermentation of Nacional x Trinitario cacao. A total of 249 microbial isolates were obtained from spontaneous culture, with Lactiplantibacillus (45 %), Saccharomyces (17 %), and Acetobacter (2 %) being the most relevant genera for fermentation. Tolerance tests were conducted to select microorganisms for the starter culture. Lactiplantibacillus plantarum exhibited the highest tolerance at pH 5 and 6 % ethanol and tolerated concentrations up to 15 % for glucose and fructose. Acetobacter pasteurianus grew at pH 2 and 6 % ethanol, tolerating high sugar concentrations of up to 15 % for glucose and 30 % for fructose, with growth observed in concentrations up to 5 % for lactic and acetic acid. Subsequently, a laboratory-scale fermentation was conducted with the formulated starter culture (SC) comprising S. cerevisiae, L. plantarum, and A. pasteurianus, which exhibited high tolerance to various stress conditions. The fermentation increased alcoholic compounds, including citrusy, fruity aromas, and floral notes such as 2-heptanol and phenylethyl alcohol, respectively 1.6-fold and 5.6-fold compared to the control. Moreover, the abundance of ketones 2-heptanone and 2-nonanone increased significantly, providing sweet green herbs and fruity woody aromas. Cacao fermented with this SC significantly enhanced the favorable aroma-producing metabolites characteristic of Fine-aroma cacao. These findings underscore the potential of tailored fermentation strategies to improve cacao product quality and sensory attributes, emphasizing the importance of ongoing research in optimizing fermentation processes for the cacao industry.

Effect of different isolation sources of Lactococcus lactis subsp. lactis on volatile metabolites in fermented milk

Lactococcus lactis subsp. lactis (L. lactis subsp. lactis) is a commonly used starter cultures in fermented dairy products, contributing distinct flavor and texture characteristics with high application value. However, the strains from different isolates have different contributions to milk fermentation. Therefore, this study aimed to investigate the influence of L. lactis subsp. lactis isolated from various sources on the volatile metabolites present in fermented milk. In this study, L. lactis subsp. lactis from different isolation sources (yogurt, koumiss and goat yogurt) was utilized as a starter culture for fermentation. The volatile metabolites of fermented milk were subsequently analyzed by headspace solid phase microextraction gas chromatography-mass spectrography (HS-SPME-GC-MS). The results indicated significant differences in the structure and abundance of volatile metabolites in fermented milk produced with different isolates (R2Y = 0.96, Q2 = 0.88). Notably, the strains isolated from goat yogurt appeared to enhance the accumulation of ketones (goat yogurt vs yogurt milk: 50 %; goat yogur vs koumiss: 27.3 %)and aldehydes (goat yogurt vs yogurt milk: 21.4 %; goat yogurt vs koumiss: 54.5 %) in fermented milk than strains isolated from koumiss and yogurt milk. It significantly promoted the production of 8 flavor substances (1 substance with OAV ≥ 1 and 6 substances with OAV > 0.1) and enhanced the biosynthesis of valine, leucine, and isoleucine. This study provides valuable insights for the application of Lactococcus lactis subsp. lactis isolated from different sources in fermented dairy production and screening of potential starter cultures.

Probiotic potential and safety analysis of lactic acid bacteria isolated from Ethiopian traditional fermented foods and beverages

BackgroundProbiotics are live microorganisms that effectively combat foodborne pathogens, promoting intestinal health when consumed in sufficient amounts. This study evaluated the probiotic potential and safety of lactic acid bacteria isolated from selected Ethiopian traditional fermented foods and beverages (Kotcho, Bulla, Ergo, Cabbage-Shamita, Borde, and Bukuri). To assess the isolates’ probiotic activity, tolerance, and survival rate under various stressful conditions, including low pH, intestinal inhibitory substances, salt concentration, bile salt, and simulated gastric/intestinal juice. The isolates were also tested for antagonistic activities against common bacterial and fungal pathogens (Staphylococcus aureus, Salmonella Typhimurium, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Candida albicans) and safety (auto-aggregation, co-aggregation, cell source hydrophobicity, hemolytic activity, DNase, and antibiotic susceptibility). The best probiotic lactic acid bacteria (LAB) were characterized to species level following standard MALDI TOF/mass spectrometry analysis.ResultsA total of 125 potentially probiotic LAB were isolated of which 17 (13.60%) isolates survived low pH (2, 2.5, and 3), bile salt (0.3%), intestinal inhibitory chemicals (phenol, bile, low acidity, pepsin, and pancreas), and simulated gastro-intestinal settings with near 60–94% survival rate. In addition, 11 best LAB isolates were further screened based on additional screening including their antimicrobial efficacy, preservative efficiency, bacteriocin production besides resistance to low acid and bile salts, and survival potential under simulated gastrointestinal conditions. All 11 LAB isolates were resistant to ampicillin, vancomycin, gentamicin, kanamycin, clindamycin, and chloramphenicol, while they were susceptible to streptomycin and tetracycline. The MALDI TOF mass spectrometry analysis result of efficient probiotic LAB grouped them under the genus Pediococcus, Enterococcus, and Lactococcus including Pediococcus pentosaceus, Enterococcus faecium, Lactococcus lactis, and Pediococcus acidilactici.ConclusionEthiopian traditional fermented foods and beverages are good sources of promising probiotic lactic acid bacteria. These isolates could serve as potential starter cultures and bio-preservative for the enhancement of the shelf life of foods. This study established the groundwork for the selection of excellent probiotics for the development and application of LAB for antibacterial action, starter culture production, and preservation activities.

Effect of exopolysaccharide producing starter culture on the characteristics of skim milk coagulum

The present study attempted to evaluate the effect of incorporating an exopolysaccharide (EPS) producing indigenous strain of lactic acid bacteria (LAB) with a non-EPS producing industrial strain of LAB on the physico-textural properties of product. For this, characteristics of the skim milk coagulum prepared using monocultures and mixed cultures were determined and compared. EPS producing Pediococcus pentosaceus DMG01as well as the non-EPS producer Lactococcus lactis were graded as weak acid producer based on Horrall Elliker test. Ability of the isolate DMG01 to ferment citrate endorsed its flavour production potential. Colony characteristics in Congo red agar indicated the indigenous isolate to be an EPS producer and industrial stain a non-EPS producer. The treatment products were prepared using EPS negative LAB (A), EPS producing P.pentosaceus (B) and a combination of these in the ratio 1:1 (C). The titratable acidity of curd B (0.96 percent LA) and curd A (0.86 per cent LA ) was significantly less than C (1.10 per cent LA). In line with the titratable acidity, pH differed significantly between the treatments. Syneresis value of A (1.72 per cent) was significantly higher than both B (1.55 per cent) and C (1.28 per cent). Penetrometer reading was also significantly higher for A (36.25mm), indicating that the curd tension of the A was significantly lower than both B and C. Scanning electron microscopy revealed extensive fusion of casein micelles in milk coagulum prepared with EPS producing starter culture. The results underscore the advantageous effect of EPS producing starters on textural characteristics of the fermented product.

Optimization of the composition of the protein-carbohydrate base of the nutrient medium for the production of monospecific bacterial starter culture of Lactobacillus casei

Mesophilic bacteria of Lactobacillus casei are used in the food industry not only to accelerate the cheese ripening, but also as a probiotic culture in functional foods. This article describes the results of studies to optimize the composition of the nutrient medium for the cultivation of mesophilic lactobacilli of Lbc. casei. The use of cheese whey as the basis of a nutrient medium to ensure the required level of energy metabolism leads to a decrease in production costs. However, cheese whey contains an insufficient amount of protein components and growth factors for the development of Lbc. casei. To solve the problem of providing mesophilic lactobacilli with adequate nutrition, cheese whey was enriched with an enzymatic milk protein hydrolyzates and yeast autolysate as a source of biologically active substances that stimulate the growth of lactobacilli. The optimized composition of the protein-carbohydrate base of the nutrient medium makes it possible to increase the biomass yield during deep liquid-phase cultivation and the initial infection dose of 1 % for 24 hours of cultivation to obtain the number of viable cells of Lbc. casei at the level of (8.5±0.2)⋅108 CFU/cm3, and as a consequence, to increase the efficiency of production of monospecific bacterial starter cultures.

Use of Apple Pomace as Substrate for Production of Lactiplantibacillus plantarum Malolactic Starter Cultures

The by-products of the food industry are an economic alternative as a source of nutrients to obtain biomass. At the same time, theiruse could solve the environmental problem related to their disposal, which is highly polluting due to their elevated biochemical oxygen demand. In this work, we seek to optimize the production of cellular biomass of two native Patagonian strains of Lactiplantibacillus plantarum (UNQLp 11 and UNQLp155), selected for its oenological and technological properties, using apple pomace (AP), a residue from the juice and cider industry. The supplementation of AP with yeast extract, salts, and Tween 80 (sAP), proved to maintain the growth of the Lpb. plantarum strains, similar to the commercial medium used to grow LAB (De Man, Rogosa, Sharpe, MRS). Cultures grown in sAP medium showed good tolerance to wine conditions (high ethanol content and low pH), demonstrated by its ability to consume L-malic acid. The subsequent inoculation of these cultures in sterile wines (Merlot and Pinot noir) was carried out at laboratory scale, evaluating cell viability and L-malic acid consumption for 21 days at 21 °C. Cultures grown in sAP media showed a similar performance to MRS media. Thus, sAP media proved to be a suitable substrate to grow oenological Lpb. plantarum strains where cultures (with high size inoculums) were able to drive malolactic fermentation, with an L-malic acid consumption higher than 90%.

Factory accounting and assessment of uncooked smoked sausages production efficiency

This article presents a research of factory accounting and its impact on efficiency of production of uncooked smoked sausages (dry salami). Those uncooked smoked sausages were just introduced into a factory production, and their method of production involved starter cultures. In course of the research, the efficiency of the project, the profitability of the project and the payback period were found. The cost of the food products newly introduced into production and the payback period of the project were found. The research showed the efficiency of the project, the profitability of the project was equal to 43%, the payback period was 7 months. The cost of Savory sausage per 1 kg is 449.80 rubles, per 1 ton is 449.800 rubles. The cost of Gourmet sausage per 1 kg is 456.59 rubles, for 1 ton is 456.590 rubles. The total cost of production of uncooked smoked sausages was 5.452.615 rubles. The use of our starter cultures in production of uncooked smoked sausages led to costs savings. The initial cost of Savory sausage was 621.78 rubles, and after reduction of its prime cost it became 449.80 rubles. The initial cost of Gourmet sausage was 610.72 rubles, and after reduction of its prime cost it became 456.59 rubles.

Natural Decomposer (MOL) developed from various banana waste and different storage times

MOL is a local microorganism or natural decomposer that is used as a starter culture in production of organic fertilizers which is known as bokashi. The advantage of using MOL is that it can be made from cheap materials or by utilizing agricultural waste so that it can increase the added value of waste as well as reduce the environmental pollution. The use of MOL as a biodecomposer in production of bokashi can accelerate the fermentation process. This study aimed to produce MOL where the characteristic is similar with commercial Effective Microorganism (EM4). This study used a factorial randomized block design (RBD) with 2 factors. First factor was the types of banana (J) consisted of three levels, namely awak banana (Musa paradisiacal var. Awak; J1), barangan banana (Musa acuminate Colla; J2), and kepok banana (Musa acuminata balbisiana Colla; J3). Second factor was the storage times consisted of three levels, namely 0 weeks after fermentation (L1), 2 weeks after fermentation (L2), and 4 weeks after fermentation (L3). The analysis carried out after fermentation included total cell counts (TCC), pH value, temperature, and organoleptic test in the form of hedonic test for color and description test for aroma. The best sample was determined based on the highest TCC, the lowest pH value and aroma using a ranking test. The best treatment was obtained from J1L2 treatment (awak banana and 2 weeks after fermentation) with 1.8 × 109 CFU/ml of TCC, 3.17 of pH and medium tapai aroma.

Isolation and Characterization of Lactic Acid Bacteria and Yeasts from Typical Bulgarian Sourdoughs

Traditional sourdoughs in Bulgaria were almost extinct during the centralized food production system. However, a rapidly developing trend of sourdough revival in the country is setting the demand for increased production and use of commercial starter cultures. The selection of strains for such cultures is based on geographical specificity and beneficial technological properties. In this connection, the aim of this study was to isolate, identify and characterize lactic acid bacteria (LAB) and yeasts from typical Bulgarian sourdoughs for the selection of strains for commercial sourdough starter cultures. Twelve samples of typical Bulgarian sourdoughs were collected from different geographical locations. All samples were analyzed for pH, total titratable acidity and dry matter content. Enumeration of LAB and yeast was also carried out. Molecular identification by 16S rDNA sequence analysis was performed for 167 LAB isolates, and 106 yeast strains were identified by ITS1-5.8S-ITS2 rRNA gene partial sequence analysis. The LAB strains were characterized according to their amylolytic and proteolytic activity and acidification capacity, and 11 strains were selected for further testing of their antimicrobial properties. The strains with the most pronounced antibacterial and antifungal activity are listed as recommended candidates for the development of starter cultures for sourdoughs or other food products.

Screening Non-Saccharomyces Yeasts as Low Ethanol Producing Starter Cultures

Non-Saccharomyces yeasts are known for their low fermentation rate in comparison to Saccharomyces cerevisiae.  In this study, non-Saccharomyces yeasts were inoculated into Chenin blanc grape must and fermented under aerobic and anaerobic conditions.  Saccharomycodes ludwigii displayed a strain-dependent fermentation rate, which yielded between 5.2% and 9.9% ethanol concentration under both conditions, albeit with residual sugar.  Aerobic conditions favoured the production of reduced ethanol which was between 5.8% and 9.7% for non-Saccharomyces yeasts in comparison to S. cerevisiae (10%).  This trend was observed for Wickerhamomyces anomalus, Stamerella bacillaris (Candida zemplinina), Metshnikowia pulcherrima, Cyberlindnera saturnus, Wickerhamomyces subpelliculosus and Cyberlindnera jadinii.  The laboratory-scale wines prepared with the aforementioned yeasts yielded ripe fruit and floral aroma attributes while other non-Saccharomyces yeasts resulted in wines with spicy, acidic and solvent aroma notes.

Comparative Study of Commercial Starter and Gum-producing Lactic Acid Bacteria Isolated from Palm-sap on Yoghurt

Yoghurt remains a fermented milk of choice globally but its desirability is limited by quality attributes and syneresis. In this study, the effect of using exopolysaccharide (EPS) producing starter cultures and EPS on the quality attribute of yoghurt produced from cow milk was examined. Two starter cultures of EPS-producing LAB were used singly and in combination in three treatments portions (YEPSLa, Lactobacillus acidophilus yoghurt; YEPSLs, Leuconostoc suionicum; YEPSLa + YEPSLs, Lactobacillus acidophilus and Leuconostoc suionicum); Yxg, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus to produced yoghurt while reference yoghurt (RY) was obtained from the market and refrigerated stored at 4oC. Sensory, proximate composition, textural, rheological properties and whey separation were carried out after 1 and 28 days only, while physicochemical and microbiological were analyzed after 1, 7, 14 and 28 days. No significant difference (p ˂0.05) between RY (8.60 ± 0.60), (7.21±0.10) and YEPSLa + YEPSLs (8.54 ± 0.71), (7.25 ± 0.21) in overall acceptability for day 1 and 28. Moisture (82.45 ± 0.12 - 81.31 ± 0.06%), fat (3.46 ± 0.01 - 3.42 ± 0.03%) and carbohydrate (13.05 ± 0.11 to 12.51 ± 0.10%) contents decreased while total solids (17.57 ± 0.12 - 17.97 ± 0.12%), ash (0.56 ± 0.02 - 0.57 ± 0.02%) and protein (3.74 ± 0.01 - 4.30%) contents increased respectively across the yoghurts. The result showed that the highest cohesiveness and syneresis was observed in YEPSLa + YEPSLs (27.52 ± 0.63) and commercial yoghurt (29.10 ± 0.31), the lowest in Yxg (16.71 ± 0.21) and YEPSLa + YEPSLs (21.50 ± 0.51). The highest viscosity was observed in YEPSLa + YEPSLs across the rotation speeds. The pH and titratable acid ranged (4.28 – 4.50; 0.90 – 1.41) while the total bacteria colony count (5.5×108 – 11.0×108cfu/ml) during 28 days storage period. Overall, EPS produced by EPS-producing LAB both In-vitro and In-vivo improve texture, mouthfeel, viscosity and reduce syneresis in yoghurt. Combine cultures of Lactobacillus acidophilus and Leuconostoc suionicum and their EPSs competed favourably with conventional starter, and other stabilizing agents in cow milk yoghurt.

Impact of Media Heat Treatment on Cell Morphology and Stability of L. acidophilus, L. johnsonii and L. delbrueckii subsp. delbrueckii during Fermentation and Processing

Manufacturers of starter cultures and probiotics aim to provide preparations with the highest possible amount of living cells and assurance of long-term storage stability. Thereby the industrial economy and thus an efficient outcome of the processes is of utmost importance. Earlier research has shown that the sterilization procedure of the microbial culture medium tremendously impacts growth performance of heating product-sensitive Lactobacillus strains. Thus, three different strains, i.e., L. acidophilus NCFM, L. johnsonii La-2801 and L. delbrueckii subsp. delbrueckii La-0704, were investigated for the influence of media heat pretreatment on cell morphology and stability during fermentation and further freeze drying and storage. The data indicate a relationship between the heating time of the culture medium, which is associated with an increase in browning reactions, and the cultural characteristics of the three strains. The resulting characteristic cell sizes of the cultures could be a major reason for the different stability properties during processing and storage that were observed. Besides the obvious relevance of the results for the production of starter cultures and probiotics, the pleomorphic phenomenon described here could also be a subject for other biotechnological processes, where heat-mediated media conversions, and thereby related cellular effects, could be a topic. Future studies have to show if further functional properties are influenced by the cell morphology and which cellular mechanisms lead to the observed pleomorphism.

Yogurts Supplemented with Juices from Grapes and Berries.

Nowadays, there is growing interest for the development of enriched dairy products with phenolic compounds derived from edible sources, mainly due to their safety and potential health benefits. Following that trend, in the present study, fruit juices (blueberry, aronia, and grape) were supplemented into yogurt as functional ingredients. The main physicochemical characteristics (pH, reducing sugars, acidity, color, and syneresis), total phenolic content, antioxidant activity, and viability of yogurt starters were monitored during production and storage. The use of juices had no significant effect on milk acidification rate and on the main physicochemical characteristics of yogurts, while resulted in increased red color. Total phenolic content increased from 30 to 33% (grape and aronia) and up to 49% (blueberry), while similar results were observed in antioxidant activity. Similar values of syneresis were presented in all yogurts, probably due to exopolysaccharide producing starter culture. Streptococcus thermophilus retained high viable counts during storage especially in yogurts with fruit juices (>108 cells g−1) revealing a possible prebiotic effect of juices. The results obtained from this study show that fruit juices (aronia, blueberry, and grape) have potential to be used in yogurt production in order to optimize the benefits of probiotic products with high phenolic compound intake.

An NMR Metabolomics Approach to Investigate Factors Affecting the Yoghurt Fermentation Process and Quality.

A great number of factors can influence milk fermentation for yoghurt production such as fermentation conditions, starter cultures and milk characteristics. It is important for dairy companies to know the best combinations of these parameters for a controlled fermentation and for the desired qualities of yoghurt. This study investigates the use of a 1H-NMR metabolomics approach to monitor the changes in milk during fermentation from time 0 to 24 h, taking samples every hour in the first 8 h and then at the end-point at 24 h. Three different starter cultures (L. delbrueckii ssp. bulgaricus, S. thermophilus and their combination) were used and two different heat treatments (99 or 105 °C) were applied to milk. The results clearly show the breakdown of proteins and lactose as well as the concomitant increase in acetate, lactate and citrate during fermentation. Formate is found at different initial concentrations depending on the heat treatment of the milk and its different time trajectory depends on the starter cultures: Lactobacillus cannot produce formate, but needs it for growth, whilst Streptococcus is able to produce formate from pyruvate, therefore promoting the symbiotic relationship between the two strains. On the other hand, Lactobacillus can hydrolyze milk proteins into amino acids, enriching the quality of the final product. In this way, better insight into the protocooperation of lactic acid bacteria strains and information on the impact of a greater heat treatment in the initial matrix were obtained. The global chemical view on the fermentations provided using NMR is key information for yoghurt producers and companies producing starter cultures.

Comparative evaluation of some herbs and their suitability for skimmed milk yoghurt and cast Kariesh cheese fortification as functional foods

The objective was to add certain herbs rich in active physiological ingredients for skimmed-milk yoghurt and cast ultrafiltration (UF)-Kariesh cheese to find out their suitability as fortifiers en route to innovate functional products. Yoghurt was made using cow's skimmed milk fortified with the milled herbal aqueous extract (10% w/w) at the level of nil (control), 1, 2, or 3% (w/w) of turmeric, sage or marjoram. Cheese was made using UF-skimmed milk concentrated, to the desired final cheese total solids (TS) % and fortified as mentioned before. Skim milk powder was used to avoid any dilution in the final TS %, whether of yoghurt milk or pre-cheese. Organoleptically, it was accepted the herbal extract providing that its level did not exceed 1.0% for yoghurt or 2% for cheese. The protein content exhibited no difference in yoghurt and reduction in cheese due to herbs because which the ash content decreased in yoghurt and increased in cheese, in those the fiber presented because of herbs. Turmeric encouraged the growth of bacterial starter culture and acid production versus marjoram or sage. The Streptococcus thermophilus count was always higher than that of Lactobacillus delbrueckii ssp. bulgaricus. But their counts in cheese were lower versus yoghurt. In conclusion, skimmed-milk yoghurt and cast UF-Kariesh cheese could meet the intended health purposes when fortified with 1% for the former or 2% for the latter using aqueous extract (10%) of sage, marjoram or rather turmeric, those of many impressive health benefits.

Improvement of Free Fat Soft Cheese Quality Using Exopolysaccharide- Producing Lactic Acid Bacteria as starter microflora

Free fat soft cheese was made from standardized buffalo's milk (control full fat 4.2% and 0.1% free fat milk). Milk were divided into eight portions, the first two treatments were made of full fat milk (control) without cheese starter (control), and the second was made of free fat milk without cheese starter (control). The other six treatments were made of free fat soft cheese with different starter cultures: A1 and A2 by using White Daily 82 and White Daily 42(acid producing starter cultures). V1 and V2 treatments were made with mixed starter of acid-producing cultures (A1) and exopolysaccharide-producing lactic acid bacteria (YF-L811and YC-X11). V3 and V4 treatments were made with mixed starter of acid-producing cultures (A2) and exopolysaccharide-producing lactic acid bacteria (YF-L811 and YC-X11). Three replicates of full and free fat soft cheese were traditionally made and stored at 5± 1°C. Samples were analyzed when fresh and after 7, 15, 30, 45, 60, 90 and 120 days of storage, and examined for chemical, microbiological, rheological and organoleptic characteristics. Results designated that, the use of exopolysaccharide-producing LAB in V1 treatment free fat soft cheese resulted in the highest soluble nitrogen / total nitrogen, soluble tyrosine and tryptophan contents, and the rate of accumulation of total volatile fatty acids compared, with all other cheese treatments. The highest lactic acid bacterial counts were detected in fresh V1 free fat soft cheese and V2. Lactic acid bacterial counts gradually decreased within 120 days of the storage. Yeast and mould counts were less than the standards within first 60 days of the storage period. Total viable bacterial counts slightly increased in all cheese samples, as the storage period progressed. Hardness, cohesiveness, chewiness and adhesiveness properties were high in control full-fat, as compared with all other free fat cheese. Free fat soft cheeses in the presence of acid producing bacteria mixed with exopolysaccharide producing-lactic acid bacteria as starter culture could be recommended

Effects of ccpA gene deficiency in Lactobacillus delbrueckii subsp. bulgaricus under aerobic conditions as assessed by proteomic analysis

BackgroundAerobic growth provides benefits in biomass yield and stress tolerance of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). Catabolite control protein A (CcpA) is a master regulator involved in the aerobic and anaerobic growth, metabolic production and stress response in L. bulgaricus, but its potential molecular mechanisms remains unclear. The aim of this study is to elucidate the role of CcpA in L. bulgaricus in aerobic growth at the proteomic perspective.ResultsThe differential proteomic analysis was performed on the L. bulgaricus ATCC11842 and its ccpA inactivated mutant strain using iTRAQ technology. A total of 132 differentially expressed proteins were obtained, among which 58 were up-regulated and 74 were down-regulated. These proteins were mainly involved in the cellular stress response, carbohydrate and energy metabolism, amino acid transport and protein synthesis, genetic information processing. Moreover, inactivation of ccpA negatively affected the expression of key enzymes involved in glycolysis pathway, while it enhanced the expression of proteins related to the pyruvate pathway, supporting the conclusion that CcpA mediated the shift from homolactic fermentation to mixed acid fermentation in L. bulgaricus.ConclusionsOverall, these results showed that the role of CcpA in L. bulgaricus as a pleiotropic regulator in aerobic metabolism and stress response. This proteomic analysis also provide new insights into the CcpA-mediated regulatory network of L. bulgaricus and potential strategies to improve the production of starter and probiotic cultures based on the metabolic engineering of global regulators.

Особенности подбора состава бактериальных заквасок для производства сыров с низкой температурой второго нагревания

Особенности подбора состава бактериальных заквасок для производства сыров с низкой температурой второго нагревания

Exopolysaccharide producing starter cultures positively influence on microbiological, physicochemical, and sensory properties of probiotic goats' milk set‐yoghurt

In the current study, the effect of two exopolysaccharide (EPS) producing starter cultures (YF-L903 and YC-X11) and a commercial starter culture (STI-12) on the physicochemical, microbiological, and sensory attributes of probiotic goats' milk set-yoghurt was evaluated after processing and storage at 4°C for 28 days. The type of starter culture had no effect (p > .05) on acidification of set-yoghurts. There were no differences (p > .05) in terms of viable cell counts in two tested set-yoghurts; more or less similar final cell counts were observed for Bifidobacterium animalis subsp. lactis BB-12 (~7.9 log cfu/g), Streptococcus thermophilus (~8.2 log cfu/g), and Lactobacillus delbrueckii subsp. bulgaricus (~7.8 log cfu/g). In situ EPS production of the starter cultures resulted goats' milk set-yoghurt with low syneresis, high apparent viscosity, and improved sensory attributes. Practical applications This study showed that in situ EPS production by EPS producing starter cultures markedly improved the quality attributes of goats' milk set-yoghurt. EPS production of starter cultures significantly reduced syneresis and improved apparent viscosity and sensory attributes of goats' milk set-yoghurt. This work can have an impact in advancing our understanding of the role of EPS producing starter within the context of goats' milk set-yoghurt production and in developing improved fermented goats' milk based dairy products. There is very little microbiological and physicochemical information on goats' milk set-yoghurt produced with EPS producing strains, and little understanding on the role of the produced EPS. To the best of our knowledge this is the first study investigating the microbiological and physicochemical characteristics of goats' milk set yoghurts produced with the help of EPS producing starter cultures. Therefore, we believe that this work can have an impact in advancing our understanding of the role of EPS producing starter within the context of goats' milk yoghurt production and in developing improved fermented goats' milk based dairy products.

Аналіз використання заквашувальних культур, здатних до синтезу екзополісахаридів, при ферментації молока

Аналіз використання заквашувальних культур, здатних до синтезу екзополісахаридів, при ферментації молока