Robust Domination of Lactobacillus sakei in Microbiota During Traditional Japanese Sake Starter Yamahai-Moto Fermentation and the Accompanying Changes in Metabolites

Strategies and Challenges of Microbiota Regulation in Baijiu Brewing

The traditional Chinese Baijiu brewing process utilizes natural inoculation and open fermentation. The microbial composition and abundance in the microecology of Baijiu brewing often exhibit unstable characteristics, which directly results in fluctuations in Baijiu quality. The microbiota plays a crucial role in determining the quality of Baijiu. Analyzing the driving effect of technology and raw materials on microorganisms. Elucidating the source of core microorganisms and interactions between microorganisms, and finally utilizing single or multiple microorganisms to regulate and intensify the Baijiu fermentation process is an important way to achieve high efficiency and stability in the production of Baijiu. This paper provides a systematic review of the composition and sources of microbiota at different brewing stages. It also analyzes the relationship between raw materials, brewing processes, and brewing microbiota, as well as the steps involved in the implementation of brewing microbiota regulation strategies. In addition, this paper considers the feasibility of using Baijiu flavor as a guide for Baijiu brewing regulation by synthesizing the microbiota, and the challenges involved. This paper is a guide for flavor regulation and quality assurance of Baijiu and also suggests new research directions for regulatory strategies for other fermented foods.

Lot-to-lot variation in the microbiota during the brewing process of kimoto-type Japanese rice wine

Kimoto-type Japanese rice wine (sake) has a wide variety of flavors, as the predominant microbes, including lactic acid bacteria (LAB) and nitrate-reducing bacteria, that spontaneously proliferate in the fermentation starter vary depending on the brewery. In this study, we traced the microbiota in four lots of starters manufactured in a newly established brewery and evaluated the lot-to-lot variation and characteristics of the microbiota in the brewery. The results of a 16S ribosomal RNA amplicon analysis showed that the starters brewed in the second brewing year had a more diverse microbiota than those in the first brewing year. Among the LAB predominated at the middle production stage, lactococci, including Leuconostoc spp., were detected in all the lots, while lactobacilli predominated for the first time in the second year. These results suggest that repeated brewing increased microbial diversity and altered the microbial transition pattern in the kimoto-style fermentation starters. Phylogenetic analyses for the LAB isolates from each starter identified Leuconostoc suionicum, Leuconostoc citreum, and Leuconostoc mesenteroides as predominant lactococci as well as a unique lactobacillus in place of Latilactobacillus sakei. We also found that a rice koji-derived Staphylococcus gallinarum with nitrate-reducing activity was generally predominant during the early production stage, suggesting that there was a case in which staphylococci played a role in nitrite production in the starters. These findings are expected to contribute to the understanding of the diversity of microbiota in kimoto-type sake brewing and enable control of the microbiota for consistent sake quality.

The community of lactic acid bacteria during kimoto-style seed mash making process and its control

Kimoto-style seed mash making processes such as the kimoto and yamahai-moto processes are driven by various microorganisms, and it is very important to make lactic acid bacteria grow stably for the brewing of a sake product with consistent quality. A model of bacterial transition from spherical lactic acid bacteria to rod-shaped lactic acid bacteria during kimoto-making has been advocated, but the model cannot explain all cases of a transition of a bacterial community during kimoto-making at various breweries. Several studies have described unique bacterial transition patterns that differ from those considered in the proposed model, and it is possible that factors such as differences in the initial bacterial community among breweries may cause the diversity of bacterial transitions. In this minireview, I summarize the research concerning the community of lactic acid bacteria during the kimoto-style seed mash making process, and I discuss how stable lactic acid fermentation can be achieved.

Kuratsuki bacteria and sake making

Kuratsuki bacteria enter during the sake-making process and interact with sake yeast until their growth is attenuated by the ethanol produced by sake yeast. Due to the interaction between kuratsuki bacteria and sake yeast, the metabolism of sake yeast changes, affecting the composition of esters and organic acids and subsequently the flavor and taste of sake. We cultivated kuratsuki bacteria and sake yeast, and performed test making at sake breweries to clarify the interaction among microorganisms in the sake-making process. We aim to propose a sake-making process that controls the flavor and taste of sake by utilizing the functions of kuratsuki bacteria.

Intraspecific difference of Latilactobacillus sakei in inflammatory bowel diseases: Insights into potential mechanisms through comparative genomics and metabolomics analyses

Inflammatory bowel diseases (IBDs) are chronic inflammatory diseases of the gastrointestinal tract that have become a global health burden. Studies have revealed that Latilactobacillus sakei can effectively alleviate various immune diseases, including colitis, rheumatoid arthritis, and metabolic disorders. Here, we obtained 72 strains of L. sakei from 120 fermentation and fecal samples across China. In total, 16 strains from different sources were initially screened in an in vitro Caco-2 model induced by dextran sulfate sodium. Subsequently, six strains (four exhibiting effectiveness and two exhibiting ineffectiveness) were selected for further validation in an in vivo colitis mouse model. The results demonstrated that L. sakei strains exhibited varying degrees of amelioration of the colitis disease process. Notably, L. sakei CCFM1267, the most effective strain, significantly restored colon length and tight-junction protein expression, and reduced the levels of cytokines and associated inflammatory enzymes. Moreover, L. sakei CCFM1267 upregulated the abundance of Enterorhabdus, Alloprevotella, and Roseburia, leading to increased levels of acetic acid and propionic acid. Conversely, the other four strains (L. sakei QJSSZ1L4, QJSSZ4L10, QGZZYRHMT1L6, and QGZZYRHMT2L6) only exhibited a partial remission effect, while L. sakei QJSNT1L10 displayed minimal impact. Therefore, L. sakei CCFM1267 and QJSNT1L10 were selected for further exploration of the mechanisms underlying their differential mitigating effects. Comparative genomics analysis revealed significant variations between the two strains, particularly in genes associated with carbohydrate-active enzymes, such as the glycoside hydrolase family, which potentially contribute to the diverse profiles of short-chain fatty acids in vivo. Additionally, metabolome analysis demonstrated that acetylcholine and indole-3-acetic acid were the main differentiating metabolites of the two strains. Therefore, the strains of L. sakei exhibited varying degrees of effectiveness in alleviating IBD-related symptoms, and the possible reasons for these variations were attributed to discrepancies in the carbohydrate-active enzymes and metabolites among the strains.

Effect of kuratsuki Kocuria on sake's taste varies depending on the sake yeast strain used in sake brewing

Although sake yeast mainly produces the taste of sake, sake brewery-inhabiting (kuratsuki) bacteria affect the taste of sake. Thus, kuratsuki bacteria may alter the metabolism of sake yeast through interactions between kuratsuki bacteria and sake yeast. This study aimed to confirm the effects of the combination of kuratsuki Kocuria TGY1127_2 and different sake yeast strains, AK25, K901, and K1801 on the taste of sake. Although the Brix and acidity during sake production using AK25 differed between sake with and without kuratsuki Kocuria, those using K901 and K1801 did not differ. Thus, sake yeast AK25 interacted with kuratsuki Kocuria and changed its characteristics of ethanol fermentation. In addition, the taste intensity changes, measured with a taste sensor TS-5000Z, showed that the effects of adding kuratsuki Kocuria varied among different sake yeasts. Thus, each sake yeast strain interacted with the kuratsuki bacterium and produced different metabolites, resulting in a change in the taste of sake. The findings of this study can lead to the brewing of sake using different types of kuratsuki bacteria which can affect the taste of sake.

Levilactobacillus brevis with High Production of Putrescine Isolated from Blue Cheese and Its Application

Polyamine intake has been reported to help extend the lifespan of animals. Fermented foods contain high concentrations of polyamines, produced by fermenting bacteria. Therefore, the bacteria, isolated from fermented foods that produce large amounts of polyamines, are potentially used as a source of polyamines for humans. In this study, the strain Levilactobacillus brevis FB215, which has the ability to accumulate approximately 200 µM of putrescine in the culture supernatant, was isolated from fermented foods, specifically the Blue Stilton cheese. Furthermore, L. brevis FB215 synthesized putrescine from agmatine and ornithine, which are known polyamine precursors. When cultured in the extract of Sakekasu, a byproduct obtained during the brewing of Japanese rice wine containing high levels of both agmatine and ornithine, L. brevis FB215 grew to OD₆₀₀ = 1.7 after 83 h of cultivation and accumulated high concentrations (~1 mM) of putrescine in the culture supernatant. The fermentation product also did not contain histamine or tyramine. The Sakekasu-derived ingredient fermented by the food-derived lactic acid bacteria developed in this study could contribute to increasing polyamine intake in humans.

A unique case in which Kimoto-style fermentation was completed with Leuconostoc as the dominant genus without transitioning to Lactobacillus

The Kimoto-style fermentation starter is a traditional preparation method of sake brewing. In this process, specific microbial transition patterns have been observed within nitrate-reducing bacteria and lactic acid bacteria during the production process of the fermentation starter. We have characterized phylogenetic compositions and diversity of the bacterial community in a sake brewery performing the Kimoto-style fermentation. Comparing the time-series changes with other sake breweries previously reported, we found a novel type of Kimoto-style fermentation in which the microbial transition differed significantly from other breweries during the fermentation step. Specifically, the lactic acid bacteria, Leuconostoc spp. was a predominant species in the late stage in the preparation process of fermentation starter, on the other hand, Lactobacillus spp., which plays a pivotal role in other breweries, was not detected in this analysis. The discovery of this new variation of microbiome transition in Kimoto-style fermentation has further deepened our understanding of the diversity of sake brewing.

A dark matter in sake brewing: Origin of microbes producing a Kimoto-style fermentation starter

Introduction

In Kimoto-style fermentation, a fermentation starter is produced before the primary brewing process to stabilize fermentation. Nitrate-reducing bacteria, mainly derived from brewing water, produce nitrite, and lactic acid bacteria such as Leuconostoc can proliferate because of their tolerance toward low temperature and their low nutritional requirements. Later, Lactobacillus becomes the dominant genus, leading to weakly acidic conditions that contribute to control yeasts and undesired bacterial contaminants. However, the sources of these microorganisms that play a pivotal role in Sake brewing have not yet been revealed. Thus, comprehensive elucidation of the microbiome is necessary.

Methods

In this study, we performed 16S rRNA amplicon sequencing analysis after sampling from floor, equipment surfaces, and raw materials for making fermentation starters, including koji, and water in Tsuchida Sake brewery, Gunma, Japan.

Results

Amplicon sequence variants (ASVs) between the external environments and the fermentation starter were compared, and it was verified that the microorganisms in the external environments, such as built environments, equipment surfaces, and raw materials in the sake brewery, were introduced into the fermentation starter. Furthermore, various adventitious microbes present in the fermentation starter of early days and from the external environments were detected in a nonnegligible proportion in the starter, which may impact the taste and flavor.

Discussion

These findings illuminate the uncharacterized microbial dark matter of sake brewing, the sources of microbes in Kimoto-style fermentation.

Latilactobacillus sakei Furu2019 and stachyose as probiotics, prebiotics, and synbiotics alleviate constipation in mice

Introduction

Slow transit constipation (STC) is a common disorder in the digestive system. This study aimed to evaluate the effects of stachyose (ST) and Latilactobacillus sakei Furu 2019 (L. sakei) alone or combined on diphenoxylate-induced constipation and explore the underlying mechanisms using a mouse model.

Methods

ICR mice were randomly divided into five groups. The normal and constipation model groups were intragastrically administrated with PBS. The ST, L. sakei, and synbiotic groups were intragastrically administrated with ST (1.5 g/kg body weight), alive L. sakei (3 × 10⁹ CFU/mouse), or ST + L. sakei (1.5 g/kg plus 3 × 10⁹ CFU/mouse), respectively. After 21 days of intervention, all mice except the normal mice were intragastrically administrated with diphenoxylate (10 mg/kg body weight). Defecation indexes, constipation-related intestinal factors, serum neurotransmitters, hormone levels, short-chain fatty acids (SCFAs), and intestinal microbiota were measured.

Results

Our results showed that three interventions with ST, L. sakei, and synbiotic combination (ST + L. sakei) all alleviated constipation, and synbiotic intervention was superior to ST or L. sakei alone in some defecation indicators. The RT-PCR and immunohistochemical experiment showed that all three interventions relieved constipation by affecting aquaporins (AQP4 and AQP8), interstitial cells of Cajal (SCF and c-Kit), glial cell-derived neurotrophic factor (GDNF), and Nitric Oxide Synthase (NOS). The three interventions exhibited a different ability to increase the serum excitatory neurotransmitters and hormones (5-hydroxytryptamine, substance P, motilin), and reduce the serum inhibitory neurotransmitters (vasoactive intestinal peptide, endothelin). The result of 16S rDNA sequencing of feces showed that synbiotic intervention significantly increased the relative abundance of beneficial bacteria such as Akkermansia, and regulated the gut microbes of STC mice. In conclusion, oral administration of ST or L. sakei alone or combined are all effective to relieve constipation and the symbiotic use may have a promising preventive effect on STC.

Latilactobacillus sakei: a candidate probiotic with a key role in food fermentations and health promotion

Latilactobacillus sakei is used extensively in industrial production and food fermentations. The species is primarily derived from fermented meat and vegetable products and is also found in human feces. Genomics and metabolomics have revealed unique metabolic pathways in L. sakei and molecular mechanisms underlying its competitive advantages in different habitats, which are mostly attributed to its flexible carbohydrate metabolism, cold tolerance, acid and salt tolerance, ability to cope with oxygen changes, and heme uptake. In recent years, probiotic effects of L. sakei and its metabolites have been identified, including the ability to effectively alleviate metabolic syndrome, inflammatory bowel disease, and atopic dermatitis. This review summarizes the genomic and metabolic characteristics of L. sakei and its metabolites and describes their applications, laying a foundation for their expanded use across the food and healthcare industries.

Diversity of Bacillus Isolates from the Sake Brewing Process at a Sake Brewery

We collected 92 isolates belonging to the genus Bacillus from the sake brewing process at Shiraki Tsunesuke Sake Brewery in Gifu, Japan to determine whether there is strain specificity at individual sake breweries. After distributing the isolates into seven groups, we observed that at least two groups (68 isolates) were kuratsuki bacteria at Shiraki Tsunesuke Sake Brewery. The kuratsuki Bacillus isolates were collected from different samples at the early and late stages of sake brewing in 2021 and 2019, respectively. These results showed that kuratsuki Bacillus entered the sake brewing process at this location. These kuratsuki Bacillus isolates had a high ethanol tolerance. Our previous paper showed the existence of kuratsuki Kocuria at Narimasa Sake Brewery in Toyama, Japan, but this study demonstrated that it is not found at Shiraki Tsunesuke Sake Brewery. Therefore, each sake brewery has specific kuratsuki bacterial strains, which are isolated with high frequency and contribute a specific flavor or taste to each sake brewery.

Co-cultivation of sake yeast and Kocuria isolates from the sake brewing process

Kocuria isolates collected from the sake brewing process have inhabited the Narimasa Sake Brewery in Toyama, Japan. To investigate the effect of these actinobacterial isolates on the growth and metabolism of sake yeast, co-cultivation of sake yeast and Kocuria isolates was performed in a medium containing tryptone, glucose and yeast extract (TGY), and a solution containing koji (steamed rice covered with Aspergillus oryzae) and glucose. In the TGY medium, the ethanol concentration and the number of living cells of each microorganism were measured. In the koji solution, the concentrations of ethanol and organic acids (citric acid, lactic acid and succinic acid) were measured. The results showed that in TGY media, the growth of each Kocuria isolate in the co-culture of the two Kocuria isolates was similar to that in each monoculture. However, the growth of both Kocuria isolates was inhibited in the co-cultures of sake yeast and Kocuria isolates. On the other hand, the growth and ethanol productivity of sake yeast did not differ between its monoculture and co-cultures with Kocuria isolates. In the koji solution, Kocuria isolates TGY1120_3 and TGY1127_2 affected the concentrations of ethanol and lactic acid, respectively. Thus, Kocuria isolates affected the microbial metabolism, but the effects were not identical between the two isolates. This strongly suggests that bacteria inhabiting a sake brewery may influence the flavor and taste of sake products of the brewery.

Genomic information of Kocuria isolates from sake brewing process

Bacteria belonging to the genus Kocuria were identified as bacteria peculiar to a sake brewery in Toyama, Japan. Comparison of the 16S rRNA gene sequences revealed two groups of Kocuria isolates. Among known species, one group was similar to K. koreensis (Kk type), and the other, K. uropygioeca (Ku type). We determined complete genomic DNA sequences from two isolates, TGY1120_3 and TGY1127_2, which belong to types Kk and Ku, respectively. Comparison of these genomic information showed that these isolates differ at the species level with different genomic characters. Isolate TGY1120_3 comprised one chromosome and three plasmids, and the same transposon coding region was located on two loci on the chromosome and one locus on one plasmid, suggesting that the genetic element may be transferred between the chromosome and plasmid. Isolate TGY1127_2 comprised one chromosome and one plasmid. This plasmid encoded an identical transposase coding region, strongly suggesting that the genetic element may be transferred between these different isolates through plasmids. These four plasmids carried a highly similar region, indicating that they share a common ancestor. Thus, these two isolates may form a community and exchange their genetic information during sake brewing.

Changes in Bacterial and Chemical Components and Growth Prediction for Lactobacillus sakei during Kimoto-Style Fermentation Starter Preparation in Sake Brewing: a Comprehensive Analysis

Kimoto-style seed mash is a traditional preparation method for sake that takes advantage of spontaneous lactic acid fermentation before the growth of yeast. Lactic acid helps decrease the pH in seed mash and control the growth of unfavorable microorganisms. In this study, we carried out a comprehensive analysis of the change in the bacterial community and chemical composition during the lactic acid fermentation stage in kimoto-style seed mash preparation. The bacterial transitions were diverse at five sake breweries, but they exhibited three patterns. Lactobacillus sakei was the dominant species in the later stage of lactic acid fermentation in all sake breweries. This species was found to be the most important bacterium for the accumulation of lactic acid, because its average production rate of lactic acid in seed mash reached 4.44 × 10^-11mg cell^-1 h^-1, which is 10 times higher than those of other species. As a result of specific growth rate analysis, it was revealed that the growth rate of L. sakei was influenced by the strain, pH, and temperature. The effects of pH and temperature were explained by the square root model, and the result indicates that the strains isolated in this study were incapable of growth below pH 3.9. The growth curve predicted using the growth model fit the actual cell density in two out of five sake breweries; however, our model did not work well for the remaining three sake breweries, and we presume that the error was caused by the strain or an unknown factor.IMPORTANCE It is important to produce lactic acid in kimoto-style seed mash; however, the bacterial transition is different depending on the sake brewery. The reason why there are diverse bacterial transitions during kimoto-style seed mash preparation for each sake brewery is unclear so far, and it causes difficulty in starting kimoto-style seed mash. Our findings indicate that the changes in pH caused by lactic acid bacteria grown prior to L. sakei in seed mash influence the growth of L. sakei and are related to the diversity of the bacterial transition. This study uses comprehensive analytical methods to reveal that there is a diversity of bacterial transition and chemical compositions in kimoto-style seed mash depending on the sake brewery and to explain the differences in bacterial transition depending on the characteristics of L. sakei.

Correlations between microbiota with physicochemical properties and volatile flavor components in black glutinous rice wine fermentation

Black glutinous rice wine (BGRW) is a popular traditional Chinese rice wine; however, the flavors profiles associated with microbiota changes during its fermentation have not yet been evaluated. In this study, we explored the correlations between microbial communities with physicochemical properties and flavor components during BGRW fermentation. High-throughput sequencing was used to identify the microbial community composition of BGRW at different fermentation stages, and physicochemical properties and volatile flavor compounds (VFCs) were identified via fermentation features testing and headspace solid phase microextraction gas chromatography mass spectrometry. First, we revealed Pantoea and Kosakonia predominated bacterial genera the early stage of BGRW fermentation, Leuconostoc, Pediococcus, Bacillus, and Lactobacillus predominated bacterial genera the later stage, while Rhizopus and Saccharomyces were the predominant fungal genera throughout fermentation. Second, total sugars, titratable acids, pH, ethanol, amino acid nitrogen, and 43 VFCs were detected during fermentation. Twenty-three VFCs were differentially produced according to the linear discriminant analysis effect size method. With the increase of the fermentation time, the kinds and contents of esters and alcohols were also increased, while acids decreased. Moreover, 12 microbial genera, Lactococcus, Pediococcus, Leuconostoc, Lactobacillus, Cronobacter, Pantoea, Weissella, Enterococcus, Rhizopus, Myceliophthora, Cystofilobasidium, and Aspergillus were found to be highly correlated (|ρ| > 0.7 and P < 0.05) with physicochemical properties and VFCs, by redundancy analysis (RDA) and two-way orthogonal partial least squares (O2PLS) analysis. Ultimately, based on the results, a metabolic map of dominant genera in BGRW was established. Our findings provided detailed information on the dynamic changes of physicochemical properties and VFCs and selection of beneficial strains to improve the quality of BGRW.

Bacterial DNA Diversity among Clear and Cloudy Sakes, and Sake-kasu

Background:

The traditional Japanese alcoholic drink, sake, is classified into two types: those that contain sediment produced during the production process (cloudy sakes) and those that do not contain such sediment (clear sakes). Leftover pressed sediment from the sake production process, sake-kasu (sake cake or sake lees), is commercially available and is highly nutritious for humans.

Objective:

The purpose of this study was to determine the difference among component bacterial DNA sequences of clear and cloudy sakes, and sake-kasu.

Methods:

We compared the 16S rDNA sequences from 44 samples of clear sake, 3 samples of cloudy sake, and 11 samples of sake-kasu.

Results:

The DNA sequences were divided into three major clusters; however, sequences in sake-kasu were located in just one cluster forming two lineages. The microbial diversity in sake-kasu was lower than that in clear and cloudy sakes, which may be because some of the contaminating bacterial cells do not lyse during the production process and remain intact, along with yeast cells, in sake-kasu.

Conclusion:

Bacterial DNA frequently detected in sake samples was from environmental bacterial contamination that occurs early in the sake production process. Contaminating bacteria are usually killed by the ethanol produced as the sake yeast grows; after which, if bacteria lyse, the bacterial DNA is released into the sake solution. However, if the bacterial cells do not lyse, they will precipitate toward the sediment. Thus, there is bacterial DNA diversity in clear and cloudy sake, but less diversity in sake-kasu.

Microbial Dynamics in Traditional and Modern Sour Beer Production

Traditional sour beers are produced by spontaneous fermentations involving numerous yeast and bacterial species. One of the traits that separates sour beers from ales and lagers is the high concentration of organic acids such as lactic acid and acetic acid, which results in reduced pH and increased acidic taste. Several challenges complicate the production of sour beers through traditional methods. These include poor process control, lack of consistency in product quality, and lengthy fermentation times. This review summarizes the methods for traditional sour beer production with a focus on the use of lactobacilli to generate this beverage. In addition, the review describes the use of selected pure cultures of microorganisms with desirable properties in conjunction with careful application of processing steps. Together, this facilitates the production of sour beer with a higher level of process control and more rapid fermentation compared to traditional methods.

Major Metabolites and Microbial Community of Fermented Black Glutinous Rice Wine With Different Starters

Black glutinous rice wine (BGRW) is a traditional Chinese rice wine that is brewed using multiple strains. However, the roles of these microorganisms, particularly their contributions to aroma formation, are poorly understood. Accordingly, the main goal of this study was to determine the microbial communities and major metabolites of different traditional fermentation starters. Anshun (AS) starter and Xingyi (XY) starter were used for BGRW to provide insight into their potential contributions to the variation in flavor and aroma. High-throughput sequencing of the microbial community using the Illumina MiSeq platform revealed significant differences during fermentation between the two starter groups. Pediococcus, Leuconostoc, and Bacillus were the dominant bacterial genera in the AS group, whereas Leuconostoc, Pediococcus, and Gluconobacter were the dominant genera in the XY group. In addition, Rhizopus, Saccharomyces, and Saccharomycopsis were the predominant fungal genera detected in both samples. The major metabolites in the two groups were identified by high-performance liquid chromatography and headspace-solid-phase microextraction gas chromatography–mass spectrometry. A total of seven organic acids along with 47 (AS) and 43 (XY) volatile metabolites were detected, among which lactic acid was the primary organic acid, and esters were the largest group in both types of wine. Principal components analysis further revealed significant differences in the dynamic succession of metabolites between the two samples. Correlation analysis showed that 22 and 17 microorganisms were strongly correlated with the production of major metabolites in AS and XY, respectively. Among them, Pediococcus, Leuconostoc, Lactobacillus, Lactococcus, and Streptococcus were shown to play crucial roles in metabolite synthesis. Overall, this study can provide a valuable resource for the further development and utilization of starters to improve the aromatic quality of BGRW.

Co-fermentation Involving Saccharomyces cerevisiae and Lactobacillus Species Tolerant to Brewing-Related Stress Factors for Controlled and Rapid Production of Sour Beer

Increasing popularity of sour beer urges the development of novel solutions for controlled fermentations both for fast acidification and consistency in product flavor and quality. One possible approach is the use of Saccharomyces cerevisiae in co-fermentation with Lactobacillus species, which produce lactic acid as a major end-product of carbohydrate catabolism. The ability of lactobacilli to ferment beer is determined by their capacity to sustain brewing-related stresses, including hop iso-α acids, low pH and ethanol. Here, we evaluated the tolerance of Lactobacillus brevis BSO464 and Lactobacillus buchneri CD034 to beer conditions and different fermentation strategies as well as their use in the brewing process in mixed fermentation with a brewer's yeast, S. cerevisiae US-05. Results were compared with those obtained with a commercial Lactobacillus plantarum (WildBrewTM Sour Pitch), a strain commonly used for kettle souring. In pure cultures, the three strains showed varying susceptibility to stresses, with L. brevis being the most resistant and L. plantarum displaying the lowest stress tolerance. When in co-fermentation with S. cerevisiae, both L. plantarum and L. brevis were able to generate sour beer in as little as 21 days, and their presence positively influenced the composition of flavor-active compounds. Both sour beers were sensorially different from each other and from a reference beer fermented by S. cerevisiae alone. While the beer produced with L. plantarum had an increased intensity in fruity odor and dried fruit odor, the L. brevis beer had a higher total flavor intensity, acidic taste and astringency. Remarkably, the beer generated with L. brevis was perceived as comparable to a commercial sour beer in multiple sensory attributes. Taken together, this study demonstrates the feasibility of using L. brevis BSO464 and L. plantarum in co-fermentation with S. cerevisiae for controlled sour beer production with shortened production time.