Fermented Mash Research Articles

Waste Bread as Raw Material for Ethanol Production: Effect of Mash Preparation Methods on Fermentation Efficiency

The issue of managing waste bread is a global concern, with significant environmental and the economic implications. The utilisation of waste bread for bioethanol production, employing energy-saving technology, could prevent these consequences and reduce the consumption of traditionally used fossil fuels. The objective of this study was to evaluate the influence of the type of waste bread (wheat and wheat–rye sourdough) and the mash preparation method on the results of alcoholic fermentation and the concentration of selected congeners in the distillates. The highest fermentation efficiency (96% of theoretical) was achieved for both types of bread through the utilisation of the pressureless starch liberation method combined with simultaneous saccharification and fermentation. The separate saccharification of starch resulted in lower process efficiencies (from 85.75 to 88.60% of theoretical). The application of the native starch hydrolysis method (without starch activation) for the fermentation of wheat bread-based mashes exhibited a higher efficiency (87.85% of the theoretical) than that observed for the wheat–rye bread-based mash sample (83.74% of theoretical). All of the obtained spirit distillates exhibited a low concentration of methanol (≤300 mg/L alcohol 100% v/v) and comply with the requirements of the EU regulation for ethyl alcohol of agricultural origin (rectified spirit).

Germplasm Resource Mining of Fen-Flavor Baijiu Brewing Micro-Organisms and Screening of Important Functional Strains

The exploration of microbial genetic resources for the production of fFen-flavor Baijiu has not only enriched the microbial library for baijiu production but has also laid the foundation for process improvement and strain optimization in baijiu brewing. In this study, a total of 177 fungal isolates were screened, including Saccharomyces cerevisiae, non-Saccharomyces cerevisiae, molds, and some pathogenic bacteria. Among them, Saccharomyces cerevisiae was the most abundant with 119 isolates, playing a major role in the fermentation of baijiu production. A total of 148 bacterial isolates were obtained from the fermentation mash samples, showing greater diversity compared to fungi. Bacillus species were the most abundant, with 94 isolates. Bacillus licheniformis, in particular, can produce a rich enzymatic system and flavor precursors, making it an important contributor to the sensory quality of baijiu. Lactic acid bacteria were the second most abundant, with 16 isolates. Additionally, five pathogenic fungal species were identified, including Candida pelliculosa, Candida lusitaniae, Fusarium oxysporum, Fusarium solani and Talaromyces marneffei. Six pathogenic bacterial species were also isolated, namely Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus xylosus, Moraxella osloensis, Actinomyces meyeri and Stenotrophomonas maltophilia. Finally, two strains of high acetate ethyl ester-producing yeast and lactate-degrading bacteria with good tolerance to temperature, pH, and ethanol concentration were identified as Saccharomyces cerevisiae and Bacillus licheniformis, respectively.

Nitrogen Availability and Utilisation of Oligopeptides by Yeast in Industrial Scotch Grain Whisky Fermentation

Scotch grain whisky is produced with a substantial proportion of unmalted grains, which can result in nitrogen deficiency for yeast in the fermentable grain mash. This study examined nitrogen source availability and utilisation by three commercial whisky strains (Saccharomyces cerevisiae) during Scotch grain whisky fermentation, focusing on oligopeptides. Peptide uptake kinetics in synthetic whisky mash with defined peptides showed that oligopeptides of up to nine amino acids were taken up by the strains, albeit with some variability between the strains. The study found that peptides with appropriate molecular weights could replace free amino acids without negatively affecting fermentation kinetics. Moreover, fermentation performance improved when additional nitrogen was provided via peptides rather than diammonium phosphate. Analysis of industrial grain mash indicated that despite low initial yeast assimilable nitrogen, residual proteolytic activity from malt increased nitrogen availability during fermentation. Approximately 30% of the nitrogen consumed by yeast during grain mash fermentation was derived from peptides. LC-HRMS peptide analysis revealed complex dynamics of peptide formation, degradation, and utilisation. This study highlights the importance of oligopeptides in ensuring optimal fermentation efficiency in Scotch grain mash and similar substrates.

Mitigating ethyl carbamate in Chinese rice wine: Role of raspberry extract

This study investigated the use of raspberry extract (RBE) in mitigating ethyl carbamate (EC) accumulation in Chinese rice wine (Huangjiu), a traditional fermented beverage. It focused on the addition of RBE to the fermentation mash and its effects on EC levels. Results indicated a significant reduction in EC production, attributed to RBE's role in altering urea and citrulline catabolism and inhibiting arginine metabolism, thus preventing EC precursors from reacting with ethanol. Additionally, RBE enhanced the rice wine's flavor profile, as shown by volatile component and amino acid analysis. This study also explored RBE's impact on Saccharomyces cerevisiae (S. cerevisiae) arginine metabolism in a simulated fermentation environment, observing increased arginine, reduced urea and citrulline levels, altered enzyme activities, and gene expression changes in arginine metabolism and transport pathways. In conclusion, it clearly demonstrated RBE's efficacy in reducing EC content in Chinese rice wine, offering valuable insights for EC reduction strategies.

Fermentation Kinetics, Potability, and Sensory Compounds of Joubidwi: An Ethnic Alcoholic Beverage

Background: Fermentation is a metabolic pathway of the breakdown of carbohydrate molecules like glucose, fructose to ethanol and various volatile and non-volatile congeners. The production of alcoholic beverages from foodstuffs like rice, cereals, fruits, maize etc., is an age-old traditional protocol. In this study, we adapted the traditional protocol of preparation of the ethnic beverage Joubidwi, with a fermentation time of 6 days, i.e., aliquots from the fermented mash (cooked rice) were collected on a daily basis from day 1 to day 6. Objectives: This study aimed to get insight into fermentation kinetics, ethanol content, carbohydrate content, antioxidant activities, bitterness, protein content, pH, colour, and turbidity of the ethnic alcoholic beverage Joubidwi and to identify the sensory compounds and polyphenol molecules. Method: UV-Visible spectroscopic methods, GC-FID and GC-MS analytics methods were used for the estimation and identification of carbohydrates, proteins, ethanol contents, and sensory compounds, respectively. Reverse phase HPLC was adapted for the identification of polyphenol molecules in Joubidwi. Results: A pseudo-first-order fermentation kinetics was observed from day 1 to day 6 fermentation of Joubidwi. Apart from ethanol content (60.48 ± 1.36 mg/mL after 72 h fermentation to 78.80 ± 1.48 mg/mL after 144 h fermentation), the beverage had nutritional values and good antioxidant properties with 22.38 to 35.11% Radical Scavenging Effect (RSE) from 1 to 6th day of fermented Joubidwi. The beverage also contained 12 sensory compounds. Gallic acid was identified as polyphenol in Joubidwi samples. Conclusion: Joubidwi is an alcoholic beverage prepared by Bodos using rice and certain herbs through a traditional fermentation process. The fermentation process follows pseudo-first-order kinetics. The beverage is potable.

Uniform experimental design optimization of liquid fermentation Baijiu mixed fermentation

In this study, corn alcohol fermentation mash was used as raw material, and different microorganisms were added to improve the flavor of liquid fermentation Baijiu. The optimum fermentation conditions of liquid fermentation Baijiu were optimized by uniform experimental design. The optimum fermentation conditions were as follows: Saccharomyces cerevisiae: non-Saccharomyces cerevisiae=3.8:1, yeast inoculation amount was 0.65 g/g, Lactobacillus inoculation amount was 1%, yeast inoculation time was 26.5 h, Lactobacillus inoculation time was 0.5 h, the total acid content was 1.943 g/L, the estimated total acid yield was 2.036 g/L, and the relative deviation was 0.077%. Compared with the three control groups, the total acid yield increased by 27.39%, 12.36% and 19.05% respectively.

Characterization of the color, physicochemical properties, organic acids, and aroma profiles of kiwifruit wines by different fermentation patterns and fining stages

The high contents of pectins, proteins, and polyphenols in the raw materials pose a challenge to the fining of fruit wines. This research investigated the impacts of juice, mash, and mash with peel fermentations on the color, organic acids, and aroma of kiwifruit wines, and further explored the effects of adding gelatin and bentonite before and during fermentations on the quality of the wines. The findings revealed that while the chroma and hue of the three fermentation patterns did not exhibit significant differences, but the contents of esters, aldehydes, and terpenes were higher in the juice and mash fermentations. The contents of total volatiles, acids, and ketones were the highest in the mash fermentation. Besides, total acidity, alcohol, chroma, hue, clarity, varieties and contents of volatiles were significantly affected by the fining stages. Clarity during fermentation fining increased from 79.72% of the control to 84.91%–88.29%. There was a minor difference in the content of the major volatiles between the control and the later stage of fermentation bentonite (LFB) fining, and the esters content of LFB fining increased by 51.87%. It indicated that mash fermentation and LFB fining were a concise and effective way to improve the clarity and flavor of kiwifruit wine.

The Influence of Prefermentation Skin Contact, Stabulation, and Skin Fermentation on the Aromatic Behaviour and Phenolic Compounds of Important Austrian White Wine Cultivars

Many varietal aromas of wine are located in the berry skin. In the present study, we evaluated four important Austrian grape varieties: Grüner Veltliner, Sauvignon Blanc, Traminer, and Pinot Blanc. We assessed whether prefermentation skin contact, fermentation with the skin (only for Grüner Veltliner), and stabulation (lees stirring; only for Sauvignon Blanc, Traminer, and Pinot Blanc) could enhance the varietal aromas of the different grape cultivars. The aim was to intensify the varietal aromas without extracting the undesirable phenols. We performed a detailed analytical characterisation of approximately 100 volatile and phenolic compounds as well as a sensory characterisation. Although mash fermentation significantly increased the spicy aromas of Grüner Veltliner, which are affected by climate change (especially the sesquiterpene rotundone), it markedly decreased the fruitiness and increased the bitterness; therefore, it cannot be recommended for this cultivar. For Sauvignon Blanc, stabulation is a possible option; the varietal aromas (thiols and methoxypyrazines) were increased in the final wines of these variants. For Pinot Blanc and Traminer, prefermentation skin contact yielded the best results: for Traminer, it produced the highest content of monoterpenes (especially z-rose oxide), and for Pinot Blanc, it produced the highest content of ethyl esters. To summarise, stabulation will not completely replace classic skin contact, and mash fermentation is certainly not an alternative for the production of standard Grüner Veltliner wine. However, additional investigations are necessary with regard to other grape varieties, terroirs, and vintages before we can make final recommendations.

Changes in phenolic composition, antioxidant, sensory and microbiological properties during fermentation and storage of maize products

In this study, we assessed the potential of maize (Zea mays) flour to serve as a substrate for the growth, metabolism, and survival of the Fresco culture cocci (Lactococcus lactis ssp. lactis, Lactococcus lactis ssp. cremoris and Streptococcus thermophilus) and Bifidobacterium spp. (B. choerinum K1/1, B. pseudolongum K4/4, B. animalis subsp. animalis J3II, B. thermophilum DSM 20212), which could result in improved nutritional and sensory properties. Maize dairy-free mashes (flavoured with saccharose or caramel) were effectively fermented with Fresco culture for 8 h at 37 °C (3 log increase of counts on average). The functionality of products was proven within the cold storage period (21 days at 6 °C) when viable cell densities of potentially probiotic bacteria were sufficient to demonstrate health-promoting effects (> 5 log CFU/mL). Fermentation process positively changed the contents and compositions of phenolic compounds. Total phenolic content was higher by about 11.5–94.68% in comparison to initial values (0 h). Caffeic acid recorded the highest increase, by about 21.7–151.7%. The antioxidant activity of fermented mashes was also improved. Overall sensory acceptance was enhanced from 2.1 (8 h) to 3.1–3.6 from 4.0 (21 d), which revealed pleasant acceptance of the final caramel products.Graphical

Proteomics analysis of enzyme systems and pathway changes during the moromi fermentation of soy sauce mash.

During the brewing of soy sauce, the conversion of multiple substances is driven by various microorganisms and their secreted enzyme systems. Soy sauce mash is an important source of enzyme systems during moromi fermentation, but the changes of enzyme systems in soy sauce mash during moromi fermentation are poorly understood. In order to explore the predominant enzyme systems existing during moromi fermentation and to explain the characteristics of the enzyme system changes, an enzymatic activities assay and 4D-label-free proteomics analysis were conducted on soy sauce mash at different stages of fermentation. The activities of hydrolytic enzymes in soy sauce mash decreased continuously throughout the fermentation process, while most of the characteristic physicochemical substances in soy sauce mash supernatant had already accumulated at the early stage of fermentation. Four hydrolytic enzymes were found to be positively correlated with important physicochemical indexes by principal component analysis and Pearson correlation analysis. The proteomics analysis revealed three highly upregulated enzymes and two enzymes that were present in important metabolic pathways throughout the fermentation process. Furthermore, it was found that Aspergillus oryzae was able to accumulate various nutrients in the soy sauce mash by downregulating most of its metabolic pathways. Enzymes present with excellent properties during the moromi fermentation period could be obtained from these results. Meanwhile, the characterization of the metabolic pathways of microorganisms during the moromi fermentation period was revealed. The results provide a basis for more scientific and purposeful improvement of moromi fermentation in the future. © 2024 Society of Chemical Industry.

Investigation on screening, identification, and fermentation characteristics of Yunnan olive in the fermented liquid utilizing five strains of Saccharomyces cerevisiae.

Refined indigenous Saccharomyces cerevisiae can enhance refinement, sophistication, and subtlety of fruit wines by showcasing exceptional regional characteristics. In order to identify exceptional indigenous S. cerevisiae strains from Yunnan olive, this study isolated 60 yeast strains from wild Yunnan olive fermentation mash. The five S. cerevisiae strains were subjected to morphological and molecular biological identification, followed by evaluation of their fermentation performance, ethanol production capacity, ester production capacity, H2S production capacity, killing capacity, and tolerance. Strains LJM-4, LJM-10, and LJM-26 exhibited robust tolerance to 6% ethanol volume fraction, pH 2.8, sucrose concentration of 400g/L, SO2 concentration of 0.3g/L, glucose concentration of 400g/L at both 40°C and 15°C. Additionally, strain LJM-10 demonstrated a faster fermentation rate compared to the other strains. Among the tested S. cerevisiae strains evaluated in this study for olive wine fermentation process in Yunnan region; strain LJM-10 displayed superior abilities in terms of ester and ethanol production while exhibiting the lowest H2S production levels. These findings suggest that strain LJM-10 holds great potential as an excellent candidate for optimizing fruit wine S. cerevisiae fermentation processes in Yunnan olive fruit wine.

THE IMPACT OF STILLAGE FILTRATE ON THE SYNTHESIS OF VOLATILE IMPURITIES OF ALCOHOL AND THE OPTIMIZATION OF THE RECTIFICATION PROCESS

The aim of this research is to determine the influence stillage filtrate on the synthesis of volatile impurities in alcohol, with subsequent removal through the rectification process in a rectification unit operating in an energy-saving mode at pressures lower than atmospheric. The study was conducted at the state enterprise (hereinafter - SE) "Kozlivsky Distillery" located at: Ternopil region, Kozlivsky district, urban-type settlement Kozliv, using gas chromatographic method for determining the content of microcomponents (acetaldehyde, methanol, fusel oil components, esters) using capillary columns. The rectification unit includes various components such as the mash column, hydroselection column, rectification column, methanol column, impurity concentration column and "zero" column. During the research, technological parameters of operation of each unit component were studied, and the concentration of organic impurities in alcohol at different stages was determined. The results of this study allow improving the efficiency of the rectification unit, which is of great importance in alcohol production. Research was conducted on the impact stillage filtrate on the synthesis of volatile impurities in alcohol during fermentation. The research was carried out with the full use iltrate of stillage at the stage of preparing the fermenting substrate. The mash had different concentrations of dry substances. The stillage filtrate was obtained by centrifugation of native stillage and its suspended matter concentration did not exceed 1%. The influence of the amount stillage filtrate and the number of cycles of its recirculation on the biosynthesis of volatile organic compounds during fermentation was studied. The research results showed that the use stillage filtrate at the stage of preparing the fermenting substrate contributes to reducing water consumption and slows down the synthesis of acetaldehyde and higher alcohols during fermentation. With repeated use stillage filtrate, the synthesis process changes, which affects the concentration of volatile organic compounds in the fermentation mash. This impact should be taken into account when selecting operating modes of the rectification unit. Therefore, to obtain high-quality rectified alcohol, it is necessary to adjust the appropriate operating mode of the rectification unit and consider the influence stillage filtrate on the fermentation process.

Metabolites analysis and new bioactive pigments from a Monascus purpureus strain with low citrinin

A Monascus purpureus strain with high mycelial biomass and no detected citrinin in liquid fermentation was selected from 20 strains. HPLC-DAD-HRMS analysis revealed that the EtOAc extract of the fermented mash contained 2 unknown compounds and 11 known metabolites of Monascus fungi. Isolations with preparative and semi-preparative HPLC resulted in four brownish red pigments. The two unknown pigments were identified with HRMS, CD, ECD, 1D and 2D NMR, and designated as monascuskaolin A (3) and B (8). The two known compounds were verified with 13C NMR as monascusazaphilone C and monasfluol B. Result of bioactivity tests showed that the two new pigments were able to significantly reduce the transcription levels of IL-1β, TNF-α, and TGF-β, and significantly promote the proliferation of 293 T cells, suggesting that they have anti-inflammatory function and may be good for human kidney. Metabolites studies suggested that M. purpureus RCEF7056 is a safe strain with functional food utilization potential.

Novel endolysin LysMP for control of Limosilactobacillus fermentum contamination in small-scale corn mash fermentation

BackgroundTraditional bioethanol fermentation industries are not operated under strict sterile conditions and are prone to microbial contamination. Lactic acid bacteria (LAB) are often pervasive in fermentation tanks, competing for nutrients and producing inhibitory acids that have a negative impact on ethanol-producing yeast, resulting in decreased yields and stuck fermentations. Antibiotics are frequently used to combat contamination, but antibiotic stewardship has resulted in a shift to alternative antimicrobials.ResultsWe demonstrate that endolysin LysMP, a bacteriophage-encoded peptidoglycan hydrolase, is an effective method for controlling growth of LAB. The LysMP gene was synthesized based on the prophage sequence in the genome of Limosilactobacillus fermentum KGL7. Analysis of the recombinant enzyme expressed in E. coli and purified by immobilized metal chelate affinity chromatography (IMAC) showed an optimal lysis activity against various LAB species at pH 6, with stability from pH 4 to 8 and from 20 to 40 °C up to 48 h. Moreover, it retains more than 80% of its activity at 10% ethanol (v/v) for up to 48 h. When LysMP was added at 250 µg/mL to yeast corn mash fermentations containing L. fermentum, it reduced bacterial load by at least 4-log fold compared to the untreated controls and prevented stuck fermentation. In comparison, untreated controls with contamination increased from an initial bacterial load of 1.50 × 107 CFU/mL to 2.25 × 109 CFU/mL and 1.89 × 109 CFU/mL after 24 h and 48 h, respectively. Glucose in the treated samples was fully utilized, while untreated controls with contamination had more than 4% (w/v) remaining at 48 h. Furthermore, there was at least a fivefold reduction in lactic acid (0.085 M untreated contamination controls compared to 0.016 M treated), and a fourfold reduction in acetic acid (0.027 M untreated contamination controls vs. 0.007 M treated), when LysMP was used to treat contaminated corn mash fermentations. Most importantly, final ethanol yields increased from 6.3% (w/v) in untreated contamination samples to 9.3% (w/v) in treated contamination samples, an approximate 50% increase to levels comparable to uncontaminated controls 9.3% (w/v).ConclusionLysMP could be a good alternative to replace antibiotics for mitigation of LAB contamination in biofuel refineries.

Efficient denitrification of liquid digestate with its indigenous microflora

It has been a common way to recycle digestate after biogas production as a biofertilizer. However, the huge generation of digestate especially its liquid part surpasses the market consumption quantity, which in turn hinders the sustainable operation of a biogas plant. Biotreatment of liquid digestate (LD) with microorganisms is one way to reduce chemical oxygen demand (COD) and nitrogen content. This study enriched three microflorae from environmental water, liquid and solid digestate. After community structure analysis, the microflora from LD itself exhibits superior nitrogen removal function to the other two microflorae, and its predominant microbial strains are from Aliidiomarina, followed by Parapedobacter. The microflorae can grow at pH range from 7 to 10. pH and ammonium concentration show synergistic effect on the growth of microflorae. The microflora from LD can completely realize nitrogen removal in man-made medium within 48 h, and remove 93.7 % ammonia nitrogen (NH3-N) and 88.1 % COD from LD at optimum C/N ratio of 9. Sodium acetate and the fermented mash from grain ethanol production process are the preferable carbon sources to improve the removal of nitrogen and COD. The re-inoculation of indigenous microflora into LD can realize 2.9∼10.9 % increase of NH3-N removal with or without addition of carbon sources, and 0.1∼11.7 % improvement on COD removal with addition of carbon sources except glycerol. It means that the enrichment of the indigenous microflora combined with the addition of proper carbon source is a potential way to enhance the nitrogen and COD removal from LD.

Spatial and temporal distribution of environmental microbiota in Chinese rice wine (Huangjiu) natural fermentation wineries

Huangjiu brewing workshop is a small ecosystem with complex microbial community growth. This micro ecosystem is the main provider of microorganisms in the process of Huangjiu fermentation. Its existence may greatly affect the quality and flavor of Huangjiu. Environmental microbial communities of the same brewing workshop in different historical periods were collected. Full-length High-throughput sequencing and Source Tracker were used to study the correlation between brewing raw materials, fermented mash and brewing environment, and to explore the involvement of environmental microorganisms in the fermentation process. The resident functional fungi in fermented Huangjiu mash were the main components of the fungal community detected in the environment. The wheat koji, tool and interior environment contributed greatly to the source of fermented fungi in Huangjiu. Compared with the bacterial community, the environmental origin of the fungal community in fermented mash was clearer. For bacteria, the increased contribution of community aggregation was attributed to the role of deterministic processes, and community structure became more stable, showing its unique role in fermentation. This study could be implemented in a more abundant natural fermentation environment, which was of great significance to control the natural fermentation process of Huangjiu.

Enhancing Protease and Amylase Activities in Bacillus licheniformis XS-4 for Traditional Soy Sauce Fermentation Using ARTP Mutagenesis.

This study was conducted to increase the enzymatic activity of Bacillus licheniformis XS-4, which was isolated from the traditional fermented mash of Xianshi soy sauce. The mutation was induced by atmospheric and room-temperature plasma (ARTP), and a mutant strain, mut80, was obtained. mut80 exhibited significant increases in protease and amylase activity by 90.54% and 143.10%, respectively, and the enhanced enzymatic activities were stably maintained after 20 consecutive incubations. Re-sequencing analysis of mut80 revealed that the mutation sites were located in 1518447(AT-T) and 4253106(G-A) in its genome, which was involved in the metabolic pathways of amino acids. The expression of the protease synthetic gene (aprX) increased 1.54 times, while that of the amylase gene (amyA) increased 11.26 times, as confirmed via RT-qPCR. Using ARTP mutagenesis, the present study proposes a highly efficient microbial resource with enhanced protease and amylase activity provided by B. licheniformis, which can potentially be used to improve the efficiency of traditional soy sauce fermentation.

Revealing the Succession of Spatial Heterogeneity of the Microbial Community during Broad Bean Paste Fermentation.

This study aimed to elaborate the assembly processes and metabolic regulation of the microbial community under the conditions of environmental factors and artificial intervention using broad bean paste (BBP) fermentation as a tractable research object. Spatial heterogenicity of amino acid nitrogen, titratable acidity, and volatile metabolites were observed between upper and lower layers after fermentation for 2 weeks. Amino nitrogen contents in the upper fermented mash reached 0.86, 0.93, and 1.06 g/100 g at 2, 4, and 6 weeks, respectively, which were significantly higher than those of mash located at the lower layer (0.61, 0.79, and 0.78 g/100 g). Moreover, higher concentrations of titratable acidity were accumulated in upper layers (2.05, 2.25 and 2.56 g/100g) than those in lower layers, and the differentiation of volatile metabolites was the greatest (R = 0.543) at 36 days, after which the BBP flavor profiles converged with the fermentation progress. The successive heterogenicity of the microbial community in the mid-late stage was also found during fermentation, and Zygosaccharomyces, Staphylococcus, and Bacillus had heterogeneous characteristics driven by sunlight, water activity, and microbial interactions. This study provided new insights into the mechanisms underlying the succession and assembly of the microbial community of BBP fermentation, which also laid new clues for researches of the microbial communities in complex ecosystems. IMPORTANCE Gaining insights into the community assembly processes is essential and valuable for the elaboration of underlying ecological patterns. However, current studies about microbial community succession in multispecies fermented food usually treat the research object as a whole, are focused exclusively on temporal dimensions, and have ignored the changes of community structure in spatial dimensions. Therefore, dissecting the community assembly process from the view of spatiotemporal dimensions will be a more comprehensive and detailed perspective. Here, we found the heterogenicity of the BBP microbial community under the traditional production technology from spatial and temporal scales, systematically analyzed the relationship between the spatiotemporal succession of community and the difference of BBP quality, and elucidated the roles of environmental factors and microbial interactions to drive the heterogeneous succession of the microbial community. Our findings provide a new insight into understanding the association between microbial community assembly and the quality of BBP.

Restoration of Choujiu Koji and evaluation of its brewing performance

Koji is used as a fermentation starter in Choujiu manufacture in northwestern China. Traditional natural Koji (NK) cultivates in open environments, which probably leads to diverse microflora, causes inconsistent quantities in Koji, then results in instable qualities of Choujiu. A native Choujiu producer has been purchasing NK from local workshop, while their Choujiu qualities fluctuate by the stability of NK.As a request from the producer, this study aimed for stable Koji and inheriting sensory traits of current products. Strains of mold, yeast, and LAB, separated from NK, were selected for Restored Koji (RK) making. Brewing performance of RK and NK were compared by analysis of the physicochemical properties and volatile flavor compounds (VFCs) in fermented mash, combined with sensory evaluation in corresponding Choujiu.Pure Koji from individual strains was separately cultured at 28 °C for 48 h, and then reconstituted for RK II at the proportion of mold Koji (M7 Koji): yeast Koji (Y3 Koji: Y4 Koji = 1:1): LAB Koji (L1 Koji) = 1:1:1, where M7 was Rhizopus oryzae, Y3 was Saccharomyces cerevisiae, Y4 was Saccharomycopsis fibuligera, and L1 was Pediococcus pentosaceus. Results showed RK II could meet the desired purpose of this study.

PEP4-Allele Modification Provides an Industrial Brewing Yeast with Malate Stress Tolerance

Acid stress is a challenging condition that yeast cells must overcome during fermentation. Enhancing the inherent tolerance of industrial Saccharomyces cerevisiae to organic acid stresses is crucial for increasing fermentation efficiency and reducing economic costs. In a previous study, we constructed a Saccharomyces cerevisiae strain SWY85S with improved tolerance to citric acid stress by modifying the second PEP4-allele. Malic acid is a dominant organic acid in grapefruit, which forms the acidic constituents of wine fermentation mash and finished products. We investigated the malic acid stress tolerance of the strain SWY85S in comparison with that of a strain with one PEP4-allele disrupted and the wild-type strain in this study. Our results revealed that the strain SWY85S demonstrated greater tolerance of malic acid stress, regardless of whether it was cultured with adequate nutrient supplies or under amino acid starvation. Moreover, the strain SWY85S performed remarkably in converting glucose to ethanol during fermentation under malic acid stress. This study provides insights into the role of a vacuolar PEP4-allele coding product in response to environmental stress and the physiological mechanism of yeast to withstand organic acid stress.