Interaction between lactic acid bacteria and yeasts in airag, an alcoholic fermented milk

Gut mycobiome in metabolic diseases: Mechanisms and clinical implication

Obesity, type 2 diabetes mellitus (T2DM) and non-alcoholic fatty liver disease (NAFLD) are three common metabolic diseases with high prevalence worldwide. Emerging evidence suggests that gut dysbiosis may influence the development of metabolic diseases, in which gut fungal microbiome (mycobiome) is actively involved. In this review, we summarize the studies exploring the composition changes of gut mycobiome in metabolic diseases and mechanisms by which fungi affect the development of metabolic diseases. The current mycobiome-based therapies, including probiotic fungi, fungal products, anti-fungal agents and fecal microbiota transplantation (FMT), and their implication in treating metabolic diseases are discussed. We highlight the unique role of gut mycobiome in metabolic diseases, providing perspectives for future research on gut mycobiome in metabolic diseases.

Valorization of Cashew Apple Waste into a Low-Alcohol, Healthy Drink Using a Co-Culture of Cyberlindnera rhodanensis DK and Lactobacillus pentosus A14-6

This study investigated the potential of microbial fermentative transforming processes in valorizing the cashew apple by-product into a low-alcohol, health-benefiting beverage. We particularly investigated the use of a non-Saccharomyces yeast, Cyberlindnera rhodanensis DK, as the main targeted microbe. At 30 °C without agitation, C. rhodanensis DK caused changes in key parameters during the fermentation of cashew apple juice (CAJ) in terms of varied pH values and initial sugar concentrations. This result indicated that pure CAJ, with pH adjusted to 6 and with the original 6.85% (w/v) total sugar content, was the most feasible condition, as glucose and fructose were mostly consumed at 12 days of fermentation. A co-culture approach with either Saccharomyces cerevisiae TISTR 5088 or Lactobacillus pentosus A14-6 was investigated to improve both physicochemical and fermentation characteristics. Co-fermentation with S. cerevisiae TISTR 5088 resulted in significantly increased ethanol accumulation to 33.61 ± 0.11 g/L, but diminished bioactive compounds, antioxidant activity, and antidiabetic potential. In contrast, co-fermentation with L. pentosus A14-6 demonstrated excellent outcomes, as it significantly increased sugar consumption and finally remained at only 4.95 g/L compared to C. rhodanensis DK alone, produced lower levels of ethanol at only 19.47 ± 0.06 g/L, and higher total titratable acid (TTA), resulting in a final pH of 3.6. In addition, co-fermentation with this lactic acid bacterium significantly enhanced bioactive compounds and antioxidant activity and also retained potential antidiabetic properties. These findings highlight the feasibility of using tailored microbial fermentation strategies to produce low-alcohol beverages with enhanced health-promoting properties from CAJ; however, product-development processes following health food regulations and sensory evaluation are necessary.

A catalog of ethanol-producing microbes in humans

Aim: Endogenous ethanol production emerges as a mechanism of nonalcoholic steatohepatitis, obesity, diabetes and auto-brewery syndrome. Methods: To identify ethanol-producing microbes in humans, we used the NCBI taxonomy browser and the PubMed database with an automatic query and manual verification. Results: 85 ethanol-producing microbes in human were identified. Saccharomyces cerevisiae, Candida and Pichia were the most represented fungi. Enterobacteriaceae was the most represented bacterial family with mainly Escherichia coli and Klebsiella pneumoniae. Species of the Lachnospiraceae and Clostridiaceae family, of the Lactobacillales order and of the Bifidobacterium genus were also identified. Conclusion: This catalog will help the study of ethanol-producing microbes in human in the pathophysiology, diagnosis, prevention and management of human diseases associated with endogenous ethanol production.

Fermented Mare Milk and Its Microorganisms for Human Consumption and Health

Mare milk is consumed by approximatively 30 million people in the world. In countries in Asia and East Europe, mare milk is mainly consumed as source of fermented products, called koumiss, airag or chigee, alcoholic beverages obtained by means of a culture of bacteria and lactose-fermenting yeasts. Recent research concerning mare milk and its derivatives deals mainly with their potential employment for human health. Studies about the isolation and characterization of Lactobacillus spp. and yeasts from koumiss have been aimed at assessing the potential functional properties of these micro-organisms and to find their employment for the industrial processing of mare milk. The aim of this literature review is to summarize recent research about microorganisms in fermented mare milk products and their potential functional properties.

Untargeted Metabolomics and Physicochemical Analysis Revealed the Quality Formation Mechanism in Fermented Milk Inoculated with Lactobacillus brevis and Kluyveromyces marxianus Isolated from Traditional Fermented Milk

Traditional fermented milk from the western Sichuan plateau of China has a unique flavor and rich microbial diversity. This study explored the quality formation mechanism in fermented milk inoculated with Lactobacillus brevis NZ4 and Kluyveromyces marxianus SY11 (MFM), the dominant microorganisms isolated from traditional dairy products in western nan. The results indicated that MFM displayed better overall quality than the milk fermented with L. brevis NZ4 (LFM) and K. marxianus SY11 (KFM), respectively. MFM exhibited good sensory quality, more organic acid types, more free amino acids and esters, and moderate acidity and ethanol concentrations. Non-targeted metabolomics showed a total of 885 metabolites annotated in the samples, representing 204 differential metabolites between MFM and LFM and 163 between MFM and KFM. MFM displayed higher levels of N-acetyl-L-glutamic acid, cysteinyl serine, glaucarubin, and other substances. The differential metabolites were mainly enriched in pathways such as glycerophospholipid metabolism, arginine biosynthesis, and beta-alanine metabolism. This study speculated that L. brevis affected K. marxianus growth via its metabolites, while the mixed fermentation of these strains significantly changed the metabolism pathway of flavor-related substances, especially glycerophospholipid metabolism. Furthermore, mixed fermentation modified the flavor and quality of fermented milk by affecting cell growth and metabolic pathways.

Endogenous Ethanol and Triglyceride Production by Gut Pichia kudriavzevii, Candida albicans and Candida glabrata Yeasts in Non-Alcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) increases with fructose consumption and metabolic syndrome and has been recently linked with endogenous ethanol production, notably by high alcohol-producing Klebsiella pneumoniae (HiAlc Kpn). Candida yeasts are the main causes of auto-brewery syndromes but have been neglected in NASH. Here, the fecal ethanol and microbial content of 10 cases and 10 controls were compared. Ethanol was measured by gas chromatography-mass spectrometry. Species identification was performed by MALDI-TOF MS, and triglyceride production was assessed by a colorimetric enzymatic assay. The fecal ethanol concentration was four times higher in patients with NASH (median [interquartile range]: 0.13 [0.05–1.43] vs. 0.034 [0.008–0.57], p = 0.037). Yeasts were isolated from almost all cases but not from controls (9/10 vs. 0/10, p = 0.0001). Pichia kudriavzevii was the most frequent (four patients), while Candida glabrata, Candida albicans, and Galactomyces geotrichum were identified in two cases each. The concentration of ethanol produced by yeasts was 10 times higher than that produced by bacteria (median, 3.36 [0.49–5.60] vs. 0.32 [0.009–0.43], p = 0.0029). Using a 10% D-fructose restricted medium, we showed that NASH-associated yeasts transformed fructose in ethanol. Unexpectedly, yeasts isolated from NASH patients produced a substantial amount of triglycerides. Pichia kudriavzevii strains produced the maximal ethanol and triglyceride levels in vitro. Our preliminary human descriptive and in vitro experimental results suggest that yeasts have been neglected. In addition to K. pneumoniae, gut Pichia and Candida yeasts could be linked with NASH pathophysiology in a species- and strain-specific manner through fructose-dependent endogenous alcohol and triglyceride production.

Untargeted metabolic footprinting reveals key differences between fermented brown milk and fermented milk metabolomes

Fermented brown milk has gained popularity because of its unique taste and flavor. Lactobacillus bulgaricus ND02 is a starter culture that has good milk fermentation characteristics. This study aimed to profile the metabolites produced during Maillard browning and to identify metabolomic differences between fermented brown milk and fermented milk produced by the ND02 strain. This study used liquid chromatography-mass spectrometry to compare the metabolomes of milk, fermented milk, brown milk, and fermented brown milk. Significant differences were observed in the abundances of various groups of metabolites, including peptides, AA, aldehydes, ketones, organic acids, vitamins, and nucleosides. The Maillard browning reaction significantly increased the intensity of a wide spectrum of flavor compounds, including short peptides, organic acids, and compounds of aldehydes, ketones, sulfur, and furan, which might together contribute to the unique flavor of brown milk. However, Maillard browning led to an increase in Nε-(carboxymethyl)lysine, which might cause negative health effects such as diabetes, uremia, or Alzheimer's disease. On the other hand, fermenting brown milk with the ND02 strain effectively countered such an effect. Finally, 5 differentially abundant metabolites were identified between fermented brown milk and fermented milk, including l-lysine, methylglyoxal, glyoxal, 2,3-pentanedione, and 3-hydroxybutanoic acid, which might together contribute to the different nutritional qualities of fermented brown milk and fermented milk. This study has provided novel information about the Maillard reaction and compared the metabolomes of the 4 types of dairy products.

Novel insight into physicochemical and flavor formation in koumiss based on microbial metabolic network

Koumiss, naturally fermented mare's milk, has a unique flavor that is affected by its resident microflora. In this study, we analyzed time-dependent changes in the microbiota and volatile metabolite profiles of koumiss using high-throughput sequencing and liquid-liquid extraction-gas chromatography-mass spectrometry. The dominant microrganisms in mare milk were Enterobacter and Rhodotorula, which were gradually suppressed, then Lactobacillus and Dekkera became the core microorganisms of koumiss. 17 FAA and 52 volatile organic compounds (VOCs) were identified during koumiss fermentation, including 19 odor active compounds and 15 differential metabolites of VOCs, mainly acids and esters, and their anabolism showed significant positive correlations with Lactobacillus and Dekkera. The microbial metabolic network showed that Lactobacillus and Dekkera were identified as the most important flavor-producing microbiota due to their significantly positive correlation with the formation of 33 and 28 flavor metabolites, respectively. These microorganisms produce enzymes that catalyze a series of metabolic pathways that generate VOCs, including carbohydrate metabolism, amino acid metabolism, and fatty acid biosynthesis. Our findings provide new guidance for the screening and application of flavor-producing microorganisms inkoumiss.

Do Kombucha Symbiotic Cultures of Bacteria and Yeast Affect Bacterial Cellulose Yield in Molasses?

Bacterial cellulose (BC) is a valuable biopolymer typically observed in Kombucha with many potential food applications. Many studies highlight yeast's roles in providing reducing sugars, used by the bacteria to grow and produce BC. However, whether yeast could enhance the BC yields remains unclear. This study investigates the effect of yeast Dekkera bruxellensis on bacteria Komagataeibacter intermedius growth and BC production in molasses medium. The results showed that the co-culture stimulated K. intermedius by ~2 log CFU/mL, which could be attributed to enhanced reducing sugar utilization. However, BC yields decreased by ~24%, suggesting a negative impact of D. bruxellensis on BC production. In contrast to other studies, regardless of D. bruxellensis, K. intermedius increased the pH to ~9.0, favoring the BC production. Furthermore, pH increase was slower in co-culture as compared to single culture cultivation, which could be the reason for lower BC yields. This study indicates that co-culture could promote synergistic growth but results in the BC yield reduction. This knowledge can help design a more controlled fermentation process for optimum bacterial growth and, ultimately, BC production.

Bacterial composition and function during fermentation of Mongolia koumiss

Koumiss is a fermented mare's milk beverage that has attracted increasing attention due to its nutritional richness and important economic value. Bacteria in koumiss play a major role in pH decreasing and reducing spoilage through bacterial inhibition. The dynamic changes in nutritional content were determined firstly during fermentation, and then the metagenomics sequencing technology was applied to profile koumiss core microbiota at the species level. We also clarified the function and effect of the bacteria on the nutritional content of the final product. We also investigated active microbial function by comparing the metagenomics of representative samples collected at different time points during the fermentation process. This study dynamically revealed the bacterial composition and function of traditional koumiss during its making process. Twenty-three major functional categories related to amino acid and fat synthesis, metabolism, and so on were identified. Functional category L (represented replication-, recombination-, and repair-related functions) was one of the most important categories with the highest relative abundance in all of the 23 major functional categories. CoG category having a significant correlation with Lactococcus piscium was the most abundant. The change in metabolic activity of bacteria at different fermentation time points showed that the metabolic activity was more active in the first 24 hr and then began to stabilize. LAB play the major role in the koumiss pH decreasing and quality improvement. The functional genes of related metabolic activity of lactic acid bacteria were more active in the first 24 hr of koumiss fermentation and then began to stabilize.

A snapshot study of the microbial community dynamics in naturally fermented cow's milk

Natural fermentation of milk is a prerequisite in the production of traditional dairy products and is considered a bioresource of fermentative microorganisms and probiotics. To understand the microbial dynamics during distinct fermentative phases, the roles of different microbes, and the relationship between bacteria and fungi, microbial community dynamics was investigated by culture-dependent and culture-independent approaches. Natural, static fermentation of milk induces the formation of the underlying curds and the superficial sour cream (Zuohe in the Mongolian language). From an overall perspective, viable LAB increased remarkably. Yeast showed an initial increase in their abundance (from 0 hr to 24 hr), which was followed by a decrease, and mold was detected at the later stages of fermentation (after 68 hr). The observed trends in microbiota variation suggest an antagonistic interaction between bacteria (LAB) and fungi (yeast and mold). The beneficial bacterial and fungal genus and species (e.g., Lactococcus, Streptococcus, Leuconostoc, Dipodascus, Lactococcus lacti, Dipodascus australiensis) are gradually increased in concentration, and the potentially detrimental microbial genus and species (e.g., Acinetobacter, Pseudomonas, Fusarium, Aspergillus, Mortierella, Acinetobacter johnsonii, Fusarium solani) decrease during the decline of bacterial and fungi diversity from natural fermentation. The study of microbial community dynamics could make a great contribution to understand the mechanism of natural fermentation of milk and the formation of curds and Zuohe, and to discover the potentially fermentative microbes for industrial starter cultures.

Microbial Interactions within the Cheese Ecosystem and Their Application to Improve Quality and Safety

The cheese microbiota comprises a consortium of prokaryotic, eukaryotic and viral populations, among which lactic acid bacteria (LAB) are majority components with a prominent role during manufacturing and ripening. The assortment, numbers and proportions of LAB and other microbial biotypes making up the microbiota of cheese are affected by a range of biotic and abiotic factors. Cooperative and competitive interactions between distinct members of the microbiota may occur, with rheological, organoleptic and safety implications for ripened cheese. However, the mechanistic details of these interactions, and their functional consequences, are largely unknown. Acquiring such knowledge is important if we are to predict when fermentations will be successful and understand the causes of technological failures. The experimental use of "synthetic" microbial communities might help throw light on the dynamics of different cheese microbiota components and the interplay between them. Although synthetic communities cannot reproduce entirely the natural microbial diversity in cheese, they could help reveal basic principles governing the interactions between microbial types and perhaps allow multi-species microbial communities to be developed as functional starters. By occupying the whole ecosystem taxonomically and functionally, microbiota-based cultures might be expected to be more resilient and efficient than conventional starters in the development of unique sensorial properties.

Fermentation Improves Calcium Bioavailability in Moringa oleifera leaves and Prevents Bone Loss in Calcium-deficient Rats

Nowadays, there is an increasing demand of healthier plant calcium supplements. Moringa oleifera leaves (MOL) are rich in calcium and thus are promising candidates for developing efficient calcium supplements. Here, using fermentation-based approaches, we developed a Moringa oleifera leaf ferment (MOLF), which contents higher levels of calcium. The therapeutic potential of the MOLF was also examined both in vitro and in vivo. Nine lactic acid bacteria and four yeasts were tested for better fermentation of MOL. Calcium-deficient rats were used for evaluating the therapeutic effects of MOLF. The results of liquid fermentation showed that the mixture of Lactobacillus reuteri, Lactobacillus acidophilus , and Candida utilis elevated the content of MOL calcium most strikingly, with the content of calcium increased nearly 2.4-fold (from 2.08% to 4.90%). The resulting MOLF was then subjected to cell experiments and animal experiments. The results showed that calcium absorption in Caco-2 cells in MOLF group was higher than that in CaCl2 group significantly. Interestingly, in calcium-deficient rats, MOLF treatment significantly increased the thickness of cortical bone, rat body weight, wet weight of the femur, and the femur bone density, whereas it decreased osteoclast numbers. These results indicate that microbial fermentation increased calcium bioavailability of MOL, promote the growth and development of calcium-deficient rats, bone calcium deposition, and bone growth; enhance bone strength; reduce bone resorption; and prevent calcium deficiency.

Electrical Conductivity, pH, Minerals, and Sensory Evaluation of Airag (Fermented Mare's Milk)

Traditional airag (fermented mare's milk) is a sour, slightly alcoholic drink handmade by Mongolian nomads. As airag is not heated after production, the fermentation continues to proceed and the taste changes rapidly. The objective of this study was to investigate the association of the sensory taste evaluation of airag with some properties-electrical conductivity (EC), pH and concentrations of macro minerals (calcium (Ca), phosphorous (P), sulfur (S), magnesium (Mg), potassium (K), and sodium (Na))-of airag. We held an airag contest in Mogod county, one of the most famous airag production areas, in order to collect samples of airag for the analysis of airag properties and to conduct an airag taste evaluation by Mongolian people. The results of the statistical analysis indicated that the EC-value was related to the evaluation score of airag. Except for EC, no statistically significant relationship between the taste score and the other properties was found in this study. It was concluded that the EC-value would be a simple measurement indicator for evaluating the quality of airag on site.

The life and times of yeasts in traditional food fermentations

Yeasts are eukaryotic microorganisms which have a long history in the biotechnology of food production, as they have been used since centuries in bread-making or in the production of alcoholic beverages such as wines or beers. Relative to this importance, a lot of research has been devoted to the study of yeasts involved in making these important products. The role of yeasts in other fermentations in association with other microorganisms - mainly lactic acid bacteria - has been relatively less studied, and often it is not clear if yeasts occurring in such fermentations are contaminants with no role in the fermentation, spoilage microorganisms or whether they actually serve a technological or functional purpose. Some knowledge is available for yeasts used as starter cultures in fermented raw sausages or in the production of acid curd cheeses. This review aimed to summarize the current knowledge on the taxonomy, the presence and potential functional or technological roles of yeasts in traditional fermented plant, dairy, fish and meat fermentations.

Identification of the predominant microbiota during production of lait caillé, a spontaneously fermented milk product made in Burkina Faso

The spontaneously fermented curdled milk product from Burkina Faso, lait caillé is prepared by traditional processing from raw unpasteurised milk. The fermentation lasts 1-3 days. This study aims to identify the predominant microbiota involved in lait caillé fermentation from cow milk. A survey on lait caillé end-products from local markets showed pH ranges of 3.5 to 4.2. Counts of total lactic acid bacteria (LAB) were 7.8 ± 0.06 to 10.0 ± 0.03 log CFU/g and yeast counts were 5.3 ± 0.06 to 8.7 ± 0.01 log CFU/g, together with considerate amounts of Enterobacteriaceae < 3.00 to 8.4 ± 0.14 log CFU/g. Sampling throughout the entire fermentation of lait caillé was performed at a traditional house-hold production site. A drop in pH from 6.7 ± 0.01 at 0 h to 4.3 ± 0.08 in the end-product (59 h) was found. Total LAB counts increased to 8.6 ± 0.02 log CFU/g in the end-product, while yeast and Enterobacteriaceae counts reached 6.4 ± 0.11 and 6.7 ± 0.00 log CFU/g, respectively. LAB and yeasts isolated during the fermentation were clustered by (GTG)₅ repetitive-PCR fingerprinting followed by 16S and 26S rRNA gene sequencing, respectively. Microbial successions were observed with Leuconostoc mesenteroides being the predominant LAB followed by Pediococcus pentosaceus and Weissella paramesenteroides at the onset, while Lactococcus lactis and Enterococcus spp. where the predominant LAB after 7 h of fermentation. During the first 18 h Candida parapsilosis was the dominant yeast species, while from 35 h to the end-product, Saccharomyces cerevisiae predominated. The microbial safety risk pointed out in this study, showed the need for implementation of good manufacturing practices including pasteurisation and use of well-defined starter cultures.

Study of bacterial and fungal community structures in traditional koumiss from Inner Mongolia

Koumiss is notable for its nutritional functions, and microorganisms in koumiss determine its versatility. In this study, the bacterial and fungal community structures in traditional koumiss from Inner Mongolia, China, were investigated. Our results demonstrated that 6 bacterial phyla represented by 126 genera and 49 species and 3 fungal phyla represented by 59 genera and 57 species were detected in 11 samples of artisanal koumiss. Among them, Lactobacillus was the predominant genus of bacterium, and Kluyveromyces and Saccharomyces dominated at the fungal genus level. In addition, there were no differences in the bacterial and fungal richness and diversity of koumiss from 3 neighboring administrative divisions in Inner Mongolia, and the bacterial and fungal community structures (the varieties and relative abundance of bacterial and fungal genera and species) were clearly distinct in individual samples. This study provides a comprehensive understanding of the bacterial and fungal population profiles and the predominant genus and species, which would be beneficial for screening, isolation, and culture of potential probiotics to simulate traditional fermentation of koumiss for industrial and standardized production in the future.

Selection and characterization of broad-spectrum antibacterial substance-producing Lactobacillus curvatus PA40 as a potential probiotic for feed additives

Lactic acid bacteria were screened for potential probiotics for use as feed additives. We obtained 3,000 isolates from feces of: cattle, dogs, goats, and infants; milk; yogurt; cheese; fermented sausages; Kimchi; and Cheonggukjang and tested their antibacterial activity toward indicator pathogens, including Bacillus cereus, Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica Enteritidis. We further tested their tolerance to artificial gastric juice (1% [w/v] pepsin, pH 2.5) and bile acid (0.1% [w/v] oxgall, pH 6.8). Six isolates exhibited strong antibacterial activity against indicator pathogens. The PA40 isolate from Kimchi exhibited marked resistance to artificial gastric juice and bile acid. The antibacterial substances produced by PA40 were stable to heat, pH, and enzymes. Strain PA40 was identified as a Lactobacillus curvatus strain using chemical tests and 16S rDNA sequencing and produced 248.4 mmol/L lactic acid after 48 hr of fermentative growth. The L. curvatus PA40 strain was also highly tolerant of the artificial gastrointestinal model system. Our results indicate that L. curvatus PA40 could be used as a potential probiotic feed additive.

Water-in-oil-in-water double emulsion for the delivery of starter cultures in reduced-salt moromi fermentation of soy sauce

This study investigated the application of water-oil-water (W₁/O/W₂) double emulsions (DE) for yeast encapsulation and sequential inoculation of Zygosaccharomyces rouxii and Tetragenococcus halophilus in moromi stage of soy sauce fermentation with reduced NaCl and/or substitution with KCl. Z. rouxii and T. halophilus were incorporated in the internal W₁ and external W₂ phase of DE, respectively. NaCl reduction and substitution promoted T. halophilus growth to 8.88 log CFU/mL, accompanied with faster sugar depletion and enhanced lactic acid production. Reducing NaCl without substitution increased the final pH (5.49) and decreased alcohols, acids, esters, furan and phenol content. However, the application of DE resulted in moromi with similar microbiological and physicochemical characteristics to that of high-salt. Principal component analysis of GC-MS data demonstrated that the reduced-salt moromi had identical aroma profile to that obtained in the standard one, indicating the feasibility of producing low-salt soy sauce without compromising its quality.

Effects of co-inoculation and sequential inoculation of Tetragenococcus halophilus and Zygosaccharomyces rouxii on soy sauce fermentation

The use of Tetragenococcus halophilus and Zygosaccharomyces rouxii as starter cultures is essential for desirable volatiles production during moromi stage of soy sauce fermentation. In this study, the effect of simultaneous and sequential inoculation of cultures in moromi fermentation models, with respect to viability, physicochemical changes, and volatiles formation (using SPME-GC/MS) was investigated. Interestingly, an antagonism was observed as T. halophilus only proliferated (3 log increase) in the presence of Z. rouxii, while Z. rouxii growth was suppressed by 4 log in concurrence with pH increase to 7.31. Final content of reducing sugars, ethanol, acetic acid, and amino nitrogen did not differ significantly (p<0.05) between co-inoculation and sequential inoculation. However, Z. rouxii promoted alcohols formation and produced a more complex aroma profile under suppression. According to Principal Component Analysis (PCA), the inoculation sequence (co-inoculation and sequential) has impacts on volatile compound profiles during moromi fermentation.

Characterization of airag collected in Ulaanbaatar, Mongolia with emphasis on isolated lactic acid bacteria

Background

Airag, alcoholic sour-tasting beverage, has been traditionally prepared by Mongolian nomads who naturally ferment fresh mares’ milk. Biochemical and microbiological compositions of airag samples collected in Ulaanbaatar, Mongolia and physiological characteristics of isolated lactic acid bacteria were investigated.

Methods

Protein composition and biochemical composition were determined using sodium dodecyl sulfate-gel electrophoresis and high performance liquid chromatography, respectively. Lactic acid bacteria were identified based on nucleotide sequence of 16S rRNA gene. Carbohydrate fermentation, acid survival, bile resistance and acid production in skim milk culture were determined.

Results

Equine whey proteins were present in airag samples more than caseins. The airag samples contained 0.10–3.36 % lactose, 1.44–2.33 % ethyl alcohol, 1.08–1.62 % lactic acid and 0.12–0.22 % acetic acid. Lactobacillus (L.) helveticus were major lactic acid bacteria consisting of 9 isolates among total 18 isolates of lactic acid bacteria. L. helveticus survived strongly in PBS, pH 3.0 but did not grow in MRS broth containing 0.1 % oxgall. A couple of L. helveticus isolates lowered pH of skim milk culture to less than 4.0 and produced acid up to more than 1.0 %.

Conclusion

Highly variable biochemical compositions of the airag samples indicated inconsistent quality due to natural fermentation. Airag with low lactose content should be favorable for nutrition, considering that mares’ milk with high lactose content has strong laxative effect. The isolates of L. helveticus which produced acid actively in skim milk culture might have a major role in production of airag.

Improving flavor metabolism of Saccharomyces cerevisiae by mixed culture with Bacillus licheniformis for Chinese Maotai-flavor liquor making

Microbial interactions could impact the metabolic behavior of microbes involved in food fermentation, and therefore they are important for improving food quality. This study investigated the effect of Bacillus licheniformis, the dominant bacteria in the fermentation process of Chinese Maotai–flavor liquor, on the metabolic activity of Saccharomyces cerevisiae. Results indicated that S. cerevisiae inhibited the growth of B. licheniformis in all mixed culture systems and final viable cell count was lower than 20 cfu/mL. Although growth of S. cerevisiae was barely influenced by B. licheniformis, its metabolism was changed as initial inoculation ratio varied. The maximum ethanol productions were observed in S. cerevisiae and B. licheniformis at 106:107 and 106:108 ratios and have increased by 16.8 % compared with single culture of S. cerevisiae. According to flavor compounds, the culture ratio 106:106 showed the highest level of total concentrations of all different kinds of flavor compounds. Correlation analyses showed that 12 flavor compounds, including 4 fatty acids and their 2 corresponding esters, 1 terpene, and 5 aromatic compounds, that could only be produced by S. cerevisiae were significantly correlated with the initial inoculation amount of B. licheniformis. These metabolic changes in S. cerevisiae were not only a benefit for liquor aroma, but may also be related to its inhibition effect in mixed culture. This study could help to reveal the microbial interactions in Chinese liquor fermentation and provide guidance for optimal arrangement of mixed culture fermentation systems.

High-throughput sequencing for the detection of the bacterial and fungal diversity in Mongolian naturally fermented cow's milk in Russia

Background

Traditional fermented dairy products are major components of the typical Mongolian diet since ancient times. However, almost all the previous studies on the microbial composition of traditional Mongolian fermented dairy products analyzed food samples from the Chinese Mongolian region and Mongolia but not the Russian Mongolian region. In this study, the bacterial and fungal community diversity of nineteen naturally fermented cow’s milk (NFCM) samples from local Mongolian families residing in Kalmykia and Chita of Russia was investigated with pyrosequencing.

Results

Firmicutes and Ascomycota were the predominant phyla respectively for bacteria and fungi. The abundance of the bacterial phylum Acidobacteria was considerably different between the samples from the two regions. At genus level, Lactobacillus and Pichia were the predominating bacterial and fungal genera, respectively, while six bacterial genera significantly differed between the Kalmykia (enrichment of Aeromonas, Bacillus, Clostridium, Streptococcus, Vogesella) and Chita (enrichment of Lactococcus) samples. The results of principal coordinate analysis (PCoA) based on the bacterial or fungal composition of the Kalmykia and Chita samples revealed a different microbiota structure between the samples collected in these two locations. The redundancy analysis (RDA) identified 60 bacterial and 21 fungal OTUs as the key variables responsible for such microbiota structural difference.

Conclusions

Our results suggest that structural differences existed in the microbiota of NFCM between Kalmykia and Chita. The difference in geographic environment may be an important factor influencing the microbial diversity of NFCM made by the Mongolians in Russia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0385-9) contains supplementary material, which is available to authorized users.

Influence of autochthonous lactic acid bacteria and enzymatic yeast extracts on the microbiological, biochemical and sensorial properties of Lben generic products

In this study we identified Lactococcus lactis subsp. lactis, Lc. lactis subsp. lactis biovar diacetylactis, Kluyveromices lactis and Saccharomyces cerevisiae as the dominant microorganisms of traditional Moroccan acid-alcoholic fermented milk named Lben. The low pH (3·8±0·3), lactose (16·8±3·4 mg/l) and lactic acid (8·16±0·6 mg/l) content indicated that a strong fermentation occurred in the traditional product which was also characterised by the substantial presence of ethanol and typical volatile carbonyl compounds (i.e., acetoin, diacetyl and acetaldehyde). Microbiological analyses of experimental Lben manufactured with selected strains (isolated from the traditional product) of Lc. lactis subsp. lactis and Lc. lactis subsp. lactis biovar. diacetylactis alone (batch A) and in combination with enzymatic extract of a K. lactis strain (batch B) indicated a good effectiveness of the starters employed (∼1010 CFU/g of lactococci after 8 h of incubation) and a significant effect of the yeast enzyme extract on lactococci viability. Despite slight changes in the physicochemical characteristics of the two Lben during the 15 d storage period, volatile compounds (i.e. ethanol, acetaldehyde, diacetyl and acetoin) were consistently higher in batch B. Moreover, sensorial analysis performed after 15 d of storage, highlighted higher odour and flavour intensity, vegetable odour and viscosity in batch B while batch A displayed higher astringency.