Traditional Fermentation Starter Research Articles

A Comparative Analysis of Aroma Profiles of Soju and Other Distilled Spirits from Northeastern Asia.

The soju (Korean traditional distilled liquor) market is increasing worldwide. However, in contrast to well-explored distilled liquors, including baijiu (China) and shochu (Japan), soju is less investigated, with limited research on its aroma characteristics. To facilitate better understanding of the aroma characteristics of soju, this study aims to overview recent research on the flavor characteristics of soju and compare data with those of baijiu and shochu, well-established products in the market. Soju is generally made using rice and nuruk (a traditional Korean fermentation starter). Previous studies have reflected that the aroma characteristics vary with raw materials' nutrition percentages, microbial taxa influenced in fermentation starters, and/or pressure reduction during distillation. The research on the aroma characteristics of baijiu, characterized by solid-state fermentation involving qu (a traditional Chinese fermentation starter), is focused on differences in regional characteristics of the flavor type. Research on the aroma characteristics of shochu has primarily demonstrated that the microbial community could contribute significantly to the development of specific aromatic compounds and/or attributes. Moreover, the association of the aroma characteristics of baijiu and shochu with their volatile compound development by the determination of selective ingredients has been examined. Understanding the current research progress can potentially facilitate the improvement in the aroma characteristics of soju.

Legendary fermented herbs: an ethnobotanical study of the traditional fermentation starter of the Chuanqing people in Northwestern Guizhou, China

BackgroundPlants that contain brewing microorganisms are used in traditional fermentation starters, which are an essential part of local diet, nutrition, life, and health. Regionally, the plant species used and the microorganisms included in traditional fermentation starters are diverse, endowing local fermented drinks with different flavors and health benefits. However, related traditional knowledge has been scarcely documented or revealed.MethodsAn ethnobotanical survey was conducted in five towns of Nayong County in northwestern Guizhou, China. Snowball sampling, semi-structured interviews, free lists, and participatory observation were used to collect information on Jiuqu Plants (JPs) and jiuqu-making techniques. The PacBio platform was used to study the microbial community structure and diversity in the Chuanqing people’s jiuqu.ResultsIn total, 225 informants were interviewed, including 116 who provided plants and technological processes for making Chinese baijiu jiuqu (CBJ) and 139 who provided information about making fermented glutinous rice jiuqu (FGRJ). This study found that older people have more abundant knowledge about CBJ plants. Poaceae was found to be the dominant family used in making CBJ and FGRJ (7 species each). Compared to individual plant parts, the whole plant is most commonly used in two kinds of jiuqu (19.5% in CBJ and 22.6% in FGRJ). The Chuanqing people’s jiuqu is used to treat dietary stagnation and indigestion. The highest relative frequency of citation of the CBJ plant was Ficus tikoua Bureau, and the counterpart of the FGRJ plant was Buddleja macrostachya Benth. The dominant bacterial species in jiuqu were Gluconobacter japonicus (YQ1, YQ4) and Pediococcus pentosaceus (YQ2, YQ3), and the dominant fungal species was Rhizopus oryzae.ConclusionFor the first time, this study documents the unique traditional jiuqu knowledge and reveals the microbial mystery behind the FGRJ of the Chuanqing people.Therefore, this study encourages the use of online social media platforms in order to spread Jiuqu culture, the use of the new media wave in order to create multimedia databases, and also suggests that local communities should develop preservation intervention programs, in addition to nurturing the inheritors in order to prevent the disappearance of traditional Jiuqu knowledge. This research contributes to the conservation and demystification of the traditional jiuqu knowledge of the Chuanqing people and lays the foundation for further research on its microbiology, nutrition, and metabolomics.

Saccharomyces cerevisiae SC-2201 Attenuates AOM/DSS-Induced Colorectal Cancer by Modulating the Gut Microbiome and Blocking Proinflammatory Mediators.

Colorectal cancer is the third most common cancer in the world today, and studies have shown that the ratio of Candida to Saccharomyces cerevisiae increased, and the abundance of S. cerevisiae in the intestines of patients with colorectal cancer decreased, which suggests that there is an imbalance in the proportion of fungi in the intestines of patients with colorectal cancer. The objective of this study was to screen S. cerevisiae isolate from traditional Chinese fermentation starters and assess its ability to ameliorate dysbiosis and to alleviate the carcinogenic process of azoxymethane/dextran sodium sulfate-induced colorectal cancer in mice model. S. cerevisiae strain SC-2201 was isolated and exhibited probiotic properties, including the ability to survive in an acidic pH environment and in the presence of bile salts in the gastrointestinal tract, as well as antioxidant activities. Oral administration of S. cerevisiae SC-2201 not only alleviated weight loss but also reduced colonic shortening and histological damage in azoxymethane/dextran sodium sulfate-induced colorectal cancer in mice. Furthermore, the administration of S. cerevisiae SC-2201 suppressed the expression of proinflammatory mediators, such as interleukin-1β, interleukin-6, cyclooxygenase-2, vascular endothelial growth factor, nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing protein 3. Specifically, the analysis of gut bacteriome showed a significant decrease in Bacteroidota and Campylobacterota levels, as well as an increase in Proteobacteria level in the colorectal cancer group, which was alleviated by supplementation with S. cerevisiae SC-2201. The analysis of the mycobiome revealed a significant increase in the levels of Basidiomycota, Apiosordaria, Naganishia, and Taphrina genera in the colorectal cancer group, which were alleviated after supplementation with S. cerevisiae SC-2201. However, the levels of Xenoramularia, Entoloma, and Keissleriella were significantly increased after administration with S. cerevisiae SC-2201. Overall, the findings of this study demonstrate that S. cerevisiae SC-2201 possesses potential probiotic properties and can effectively attenuate the development of colorectal cancer, highlighting its cancer-preventive potential. This is the first report of a S. cerevisiae strain isolated from traditional Chinese fermentation starters which showed good probiotic properties, and mitigated azoxymethane/dextran sodium sulfate-induced colorectal cancer by modulating the gut microbiome and blocking proinflammatory mediators in mice.

Extraction of Heat-Stabilised Defatted Rice Bran Protein by Solid-State Fermentation Using Heterofermentative Microbes from Traditional Asian Starters.

Heat-stabilised defatted rice bran (HSDRB) is a primary by-product of rice bran oil extraction industry and a nutritious source of protein. However, despite the unique nutritional profile of rice bran protein, the protein-rich by-product, HSDRB is underutilised as a low-value animal feed. Research on protein extraction from HSDRB by enzymatic hydrolysis has attracted the attention of numerous scientists. However, a cost-effective extraction method is required to mitigate the high costs associated with the use of enzymes. Therefore, we have presented an alternative economical and natural approach for protein extraction from HSDRB by solid-state fermentation (SSF) with heterofermentative microbes. SSF of HSDRB with two types of traditional Asian fermentation starters, namely loog-pang and koji, were evaluated for enzyme production and their efficacy in extracting proteins from HSDRB. For this purpose, HSDRB fermentation was carried out for 0, 12, 24, 48, 72 and 96 h followed by 24-hour hydrolysis to evaluate the extracted rice bran protein. In addition, microbiome diversity in the fermentation starters was also determined by metagenomic sequencing of 16S rRNA and internal transcribed spacer to identify bacteria and fungi, respectively. The microbial community in the fermentation starters showed the dominance of lactic acid bacteria (LAB) such as Bacillus subtilis in loog-pang and Streptococcus lutetiensis, Bacillus pumilus, Lactococcus cremoris, Lactococcus garvieae and Pediococcus pentosaceus in koji, while yeast species Saccharomycopsis fibuligera and Saccharomyces cerevisiae dominated the fungal diversity in loog-pang and koji starters, respectively. The results suggest that loog-pang and koji can produce cellulase, neutral and acid proteases during fermentation. Despite the discrepancy in their microbial diversity and the enzyme activity during SSF, both starters could effectively increase protein extraction from HSDRB. A positive relationship between the SSF duration and extracted protein was observed. During SSF with loog-pang and koji after 72 h followed by 24-hour hydrolysis, 65.66 and 66.67 % protein was extracted from HSDRB, respectively. The amino acid analysis of the protein hydrolysate produced by the non-fermented and fermented methods showed no difference and had an abundance of glutamic and aspartic acids, leucine, arginine, alanine and glycine amino acids, which accounted for approx. 58 % of the total amino acids. Loog-pang and koji (traditional Thai and Japanese fermentation starters, respectively) were found to be effective in extracting proteins from HSDRB by SSF although they are inexpensive microbial enzyme sources. Future research aimed at scaling up HSDRB protein extraction for usage in industrial applications can draw on our results.

Effects of Main Nutrient Sources on Improving Monascus Pigments and Saccharifying Power of Monascus purpureus in Submerged Fermentation

Hong Qu (HQ), obtained through fermentation of various grains using Monascus spp., has been widely utilized as the main and characteristic initial saccharification and traditional fermentation starter in the food brewing industry. The quality, color, and flavor of HQ and HQ wine are closely related to the saccharifying power (SP) and Monascus pigments (MPs) of Monascus spp. In this study, to optimize the culture medium in submerged fermentation by M. purpureus G11 for improving SP and MPs, the effects of carbon source, nitrogen source, inorganic salts, and vitamins on SP activity and biosynthesis of MPs were explored through single-factor analysis and response surface Box–Behnken experiments. The results showed that the optimal medium composition was 6.008% rice powder, 1.021% peptone, 0.0049% CuSO4, and 0.052% vitamin B1. Validation experiments performed under the optimized fermentation conditions showed a significant increase in MPs and SP by 14.91% and 36.24%, with maximum MPs and SP reaching 112.61 and 365.12 u/mL, respectively. This study provides a theoretical basis for enhancing MPs and SP in M. purpureus for HQ production, to improve the production efficiency and shorten the production cycle of HQ-related fermentation products.

Characterization of physicochemical properties, volatile compounds and microbial community structure in four types of Daqu

Daqu is one of the most important fermentation starters for Baijiu production, and different types of Daqu have been reported. However, the different types of Daqu are poorly understood. In the present study, four types of Daqu were thoroughly characterized based on biochemical composition, volatile compounds and microbial community structure. Significant differences were observed in physicochemical properties in the four types of Daqu analyzed herein (p < 0.05). Moreover, 48 volatile components were detected in samples, thus enabling the identification of 18 discriminant markers of volatile compounds in the four types of Daqu. In addition, differences in the microbial community structure of four types of Daqu were observed, including 46 differential species. Fungi had a great influence on carbon metabolism potential, and peak temperature of Daqu was negatively correlated with carbon metabolism capacity. Conversely, bacteria had a more notable effect on nitrogen metabolism, and peak temperature of four types of Daqu was positively correlated with nitrogen metabolism capacity. Thus, the findings discussed herein shed a light onto the differences of four types of Daqu, thereby contributing to expanding the current knowledge on the traditional industrial fermentation starter for Baijiu production.

Gamma-aminobutyric acid (GABA) promotes characteristics of Levilactobacillus sp. LB-2

γ-Aminobutyric acid (GABA) is a pharmaceutical, bioactive amino acid that can be produced by lactic acid bacteria (LAB), but the yield of GABA is still limited by several reasons. In this study, a GABA-producing LAB strain Levilactobacillus sp. LB-2 (OP890629) was isolated from a Chinese traditional dough fermentation starter of Jiaozi. When subjected to GABA production optimization applying one-factor-at-a-time (OFAT) and response surface method (RSM), the temperature, pH, and L-monosodium glutamate (L-MSG) concentration for GABA production were set as 37 °C, pH 4.5, and 2.5 g/L, respectively. The maximum amount of GABA produced by strain Levilactobacillus sp. LB-2 was 49.42 g/L, which was 3.5-fold higher than that before optimization of 14.19 g/L. The GABA content of steamed bread made by Levilactobacillus sp. LB-2 significantly increased. Thus, strain Levilactobacillus sp. LB-2 could be used for the production of GABA or applied for the development and improvement of GABA-enriched foods.

Effects of cassava chips (Manihot esculenta Crantz) and rain tree pods (Samanea saman) fermented with traditional fermentation starter (loog-pang kaomark) on growth performance, rumen fermentation, and microbial population in goats

To obtain guidelines for improving the quality of animal feed on production performance, rumen fermentation, and microbial population in goats. A total of 16 native-bore crossbred goats were used. A randomized complete block design (RCBD) was planned to compare four supplementation forms. There were four different loog-pang kaomark fermented cassava chips and rain tree pods (CRFLK) at proportions 100:0, 60:40, 50:50, and 40:60, respectively. The results of this study found that rice straw intake in terms of kg was higher in goats fed CRFLK 50:50, 60:40, and 40:60. While CP, NDF, and ADF digestibility were increased in goat fed CRFLK 50:50 and 40:60. The concentration of acetic acid was decreased by supplementation of CRFLK (p < 0.05) whereas NH3-N and propionic acid were increased (p < 0.05) by goat fed CRFLK. However, CH4 was decreased (p < 0.05) as a result of supplementation of CRFLK. The goat fed CRFLK decreased the protozoal population (p < 0.05). Moreover, the bacteria population was increased by fed with CRFLK (p < 0.05). This study concluded that feeding concentrate inclusion with CRFLK 50:50 and 40:60 resulted in higher propionic acid, CP digestibility, and lowest CH4 production.

Enzyme activity of Aspergillus section Nigri strains isolated from the Korean fermentation starter, nuruk.

Aspergillus section Nigri is a fungus used industrially because of its ability to produce enzymes such as cellulolytic, amylolytic and proteolytic enzymes. In this study, we obtained twenty-eight strains of Aspergillus section Nigri from the traditional Korean fermentation starter, nuruk, which is known as a mixed culture of enzymatic filamentous fungi and yeasts. All strains were identified as Aspergillus section Nigri through combined phylogenetic analysis using partial β-tubulin and calmodulin gene sequences. The cellulase, amylase and protease activities of Korean strains were measured and compared with ten reference strains of Aspergillus niger. Most Korean strains showed higher cellulolytic activity than reference strains, and Aspergillus neoniger KCN5 showed the highest β-glucosidase activity. Two-thirds of the Korean strains showed similar levels of α- and glucoamylase activity as the reference strains. The protease activity of Aspergillus section Nigri strains was the highest at pH 3.0, and A. niger KSJ2 showed the highest acidic protease activity. By comparing ten reference strains and twenty-eight Korean strains, our results suggested useful Aspergillus section Nigri strains from nuruk with high enzyme activity, such as KCN5 and KSJ2, and their potential for industrial applications as enzyme producers.

Inulin 분해효모 Wickerhamomyces anomalus JS01과 Saccharomyces cerevisiae KMBL7001의 혼합발효에 의한 돼지감자(Helianthus tuberosus L.)를 첨가한 약주의 발효 특성

Jerusalem artichoke (JA, Helianthus tuberosus L.) is a promising functional food material. JA consists of inulin and fructo-oligosaccharide which are indigestible carbohydrates in human. Previous research has develop various food products supplemented with JA, however no studies have involved yakju (Korean traditional rice wine) using JA because Saccharomyces cerevisiae cannot utilize inulin. We isolated several inulin-degrading non-Saccharomyces yeasts using nuruk (a traditional Korean fermentation starter). The isolate with the highest inulinase activity was Wickerhamomyces anomalus JS01 with 538.14 Unit/mL after 72 hours of incubation. To identify whether the inulin-degrading non-Saccharomyces yeast could improve yakju quality, W. anomalus JS01 and S. cerevisiae KMBL7001 were co-fermented to produce yakju supplemented with JA. We investigated the fermentation characteristics. At the completion of the fermentation process, the yakju co-fermented with W. anomalus JS01 and S. cerevisiae KMBL7001 (co-fermented yakju) had similar fermentation characteristics including pH, reducing sugar, alcohol, and organic acid contents compared to yakju fermented with S. cerevisiae KMBL7001 (control yakju). Moreover, co-fermented yakju had higher total amino acid contents compared with the control yakju. The W. anomalus JS01 digested some inulin into fructose which was fermented. Conversely, the control wine did not ferment any inulin during fermentation. As a result of the sensory evaluation, the co-fermented yakju obtained higher scores in all the sensory categories, suggesting that supplementing with JA and utilizing inulin-degrading yeast could improve yakju quality.

The Probiotic Effects of the Saccharomyces cerevisiae 28-7 Strain Isolated from Nuruk in a DSS-Induced Colitis Mouse Model.

Probiotics are microorganisms that can benefit host health when ingested in a live state, and lactic acid bacteria are the most common type. Among fungi, Saccharomyces boulardii (SB) is the only strain known to have a probiotic function with beneficial effects on colitis; however, information on other probiotic yeast strains is limited. Therefore, this study aimed to discover yeast strains expressing intestinal anti-inflammatory activities by exhibiting probiotic properties in dextran sodium sulfate (DSS)-induced colitis mice model. Nuruk (Korean traditional fermentation starter) containing various microbial strains was used as a source for yeast strains, and S. cerevisiae 28-7 (SC28-7) strain was selected with in vitro and in vivo characteristics to enable survival in the intestines. After 14 days of pretreatment with the yeast strains, DSS was co-administered for six days to induce colitis in mice. The results revealed that the disease activity index score was lowered by SC28-7 treatment compared to the DSS group, and the colon length and weight/length ratio were recovered in a pattern similar to that of the normal group. SC28-7 administration significantly reduced the secretion of pro-inflammatory cytokines in the serum and modified the mRNA expression of inflammatory cytokines (interleukin-1β, transforming growth factor-β, and interferon-γ) and proteins involved in gut barrier functions (mucin 2, mucin 3, zonula occludens-1, and occludin) in colon tissues. These results indicate that SC28-7 attenuates DSS-induced colon damage and inflammation, supporting its future use as a probiotic yeast for treating and preventing intestinal inflammatory diseases such as inflammatory bowel disease.

누룩 미생물 천이와 품질 특성 분석

Nuruk is a traditional Korean fermentation starter containing various microbes; it is utilized for the synthesis of alcoholic beverage. In this study, the changes in the quality characteristics and microbial community during the cultivation period of nuruk were analyzed. The results indicated that the fungal richness, expressed as Chao 1, from 70.0 to 19.3 on day 10 and subsequently increased to 35.0 on day 30 of cultivation. The content ratio of Aspergillus sp., Rhizopus sp. and Saccharomycopsis sp. increased with the progress of cultivation. Among the fungi, the content of the Aspergillus genus increased from 0.01% before cultivation to 70.4 %. Among the bacteria, the content of the Pantoea genus increased to 69.76% on day 7 and decreased to 44.80% on day 14. Considering the enzyme activity, saccharogenic power, α-amylase and carboxy peptidase exhibited the highest activity on day 7 while lipase exhibited the highest activity on day 14. Considering only the enzyme activity, the results indicated that it would be appropriate to terminate cultivation before day 14. The traditional cultivation period of nuruk is approximately 14 days; However, it is necessary to determine a suitable cultivation period for the application of nuruk as enzyme source.

The volatile profiles and microbiota structures of the wheat Qus used as traditional fermentation starters of Chinese rice wine from Shaoxing region

Wheat Qu is used as a fermentation starter in Chinese rice wine brewing and plays important roles on the quality and flavor of the product. The aim of this study was to thoroughly investigate and compare ten traditional wheat Qus collected from different Chinese rice wine manufacturers in Shaoxing region in terms of their hydrolytic enzyme activities, volatile profiles and microbiota structures. Significant variation in the enzymatic activities (glucoamylase, amylase and protease) and volatile components were observed among the samples. Single molecule real-time DNA sequencing technology (SMRT) and culture dependent approach were combined for the first time to investigate the microbial communities in traditional wheat Qus. SMRT indicated that 4 bacterial genera, including Saccharopolyspora, Staphylococcus, Bacillus and Pantoea, and 5 fungal genera, including Aspergillus, Wickerhamomyces, Candida, Alternaria and Fusarium, dominated the wheat Qus and were detected in all ten samples. On the other hand, Staphylococcus gallinarum and Lichtheimia ramose were found to be the most abundant bacterial and fungal species by culture dependent method. Moreover, the potential correlations between microorganisms and volatiles of wheat Qus were also explored using partial least squares regression. Finally, this study provided detailed insight into the microbial communities and volatile profiles presented in wheat Qu.

PH Changes Have a Profound Effect on Gene Expression, Hydrolytic Enzyme Production, and Dimorphism in Saccharomycopsis fibuligera.

Saccharomycopsis fibuligera is an amylolytic yeast that plays an important role within nuruk (a traditional Korean fermentation starter) used for the production of makgeolli (Korean rice wine), which is characterized by high acidity. However, the effect of pH change (neutral to acidic) on the yeast cell to hyphal transition and carbohydrate-hydrolyzing enzyme activities for S. fibuligera has not been investigated yet. In this study, S. fibuligera strains were cultured under the different pH conditions, and the effect on the enzyme production and gene expression were investigated. An acidic pH induced a hyphal transition from yeast cell of S. fibuligera KPH12 and the hybrid strain KJJ81. In addition, both strains showed a gradual decrease in the ability to degrade starch and cellulose as the pH went down. Furthermore, a transcriptome analysis demonstrated that the pH decline caused global expression changes in genes, which were classified into five clusters. Among the differentially expressed genes (DEGs) under acidic pH, the downregulated genes were involved in protein synthesis, carbon metabolism, and RIM101 and cAMP-PKA signaling transduction pathways for the yeast-hyphal transition. A decrease in pH induced a dimorphic lifestyle switch from yeast cell formation to hyphal growth in S. fibuligera and caused a decrease in carbohydrate hydrolyzing enzyme production, as well as marked changes in the expression of genes related to enzyme production and pH adaptation. This study will help to elucidate the mechanism of adaptation of S. fibuligera to acidification that occur during the fermentation process of makgeolli using nuruk.

Fungal community diversity and fermentation characteristics in regional varieties of traditional fermentation starters for Hong Qu glutinous rice wine

Hong Qu glutinous rice wine (HQ wine) is a traditional alcoholic beverage produced in China by fermenting cooked rice using a fermentation starter prepared with the fungus Monascus purpureus. This starter (Hong Qu, HQ) is made empirically by open spontaneous fermentation that is hard to control and standardize, resulting in inconsistent wine quality. This study investigates representative HQ samples from a large geographic region. It explores fungal microbiome compositions, identifies characteristic differences important for the production of various HQ wine styles, and reveals the key fungi responsible for HQ wine fermentation characteristics. The source of the HQ inoculum was found to be the main factor influencing fungal community composition and diversity, followed by processing technology and geographical distribution. Linear discriminant analysis effect size (LEfSe) uncovered 14 genera as potential biomarkers to distinguish regional varieties of HQ. Significant differences were also found in fermentation characteristics such as liquefying power (LP), saccharifying power (SP), fermenting power (FP), total acid content (TA) and liquor-producing power (LPP). The key fungi responsible for LP (5 genera), SP (3 genera), FP (1 genera), LPP (4 genera), and TA (4 genera) were determined using redundancy correlation analysis. Finally, Spearman’s correlation analysis indicated that LPP shows a strong positive correlation with FP and LP, while TA displays a strong negative correlation with FP. The results of this study may be utilized to prepare consistently high quality, next-generation HQ by better controlling fungal community structures, and to design fermentation processes for HQ wines with desirable oenological characteristics.

Laboratory-scale fermentation and multidimensional screening of lactic acid bacteria from Daqu

Lactic acid bacteria (LAB) are abundant in Daqu, a Chinese traditional fermentation starter primarily for the production of Baijiu. The fermentation characteristics of LAB and their contribution to flavor compounds in alcoholic fermentation were studied using a multidimensional screening procedure to select the LAB and apply them to alcoholic fermentation. The LAB strains isolated from Daqu were characterized for tolerance to pH 3 and 12% ethanol, the yield of amylase and esterase, and the capacity to utilize sugar in sorghum media. After multivariate statistical analysis, strains were selected for alcoholic fermentation on a laboratory-scale to confirm their roles in the production of flavor compounds using HS-SPME-GCMS. A total of 59 LAB strains were isolated from Daqu. Eleven LAB species belonging to 4 genera were identified: Lactobacillus, Pediococcus, Weissella and Enterococcus. Among them, L. plantarum E2 and E11, W. paramesenteroides E27, and P. pentosaceus E48 were selected and inoculated for alcoholic fermentations. Ethyl acetate, ethyl lactate, tetramethyl-pyrazine and 4-ethyl-2-methoxy-phenol increased significantly after fermentation with E2, E11 and E48. This study showed that a systematic screening process for indigenous LAB strains could be applied to Baijiu fermentation for flavor enhancement and quality control as well as construction of a Daqu synthetic microbial community.

누룩곰팡이 Aspergillus oryzae OF5-20를 이용한 쌀 품종별 고상종국제조 및 품질특성

The quality characteristics of solid starters manufactured from two types of rice samples have been reported herein. The rice samples were inoculated with Aspergillus oryzae OF5-20. It was isolated from ‘Nuruk’, a traditional fermentation starter, and exhibited high enzyme activity. The water absorption rate of rice, the raw material, reached the maximum within 160 min at ‘Samgwang’ and in 10 min at ‘Jeonju 615’. The quality evaluation tests revealed that among the for two solid starters, ‘Samgwang’ and ‘Jeonju 615’, Samgwang exhibited a higher acidity and amino acidity. As a result of the enzyme activity according to the inoculation ratio of A. oryzae OF5-20, the α-amylase showed the highest activity in ‘Samgwang’ solid starter inoculated with 4% of A. oryzae OF5-20 and ‘Jeonju 615’ solid starter with 6% inoculation. The glucoamylase activity was 1.4 times higher when the solid starter was inoculated with 4% of the liquid fungus (‘Samgwang’, 1,592.8 unit/g) than the enzyme activity when the solid starter was inoculated with 2% of the liquid fungus (1,137.8 unit/g). Since organic acids have a high ratio of citric acid and amino acids are composed of 20 kinds, such as glutamic acid, alanine, and phenylalanine, the solid starter, according to rice varieties, showed a difference in the formation of organic acids and free amino acids. Therefore, this research is expected to contribute to the improvement of the depressed starter industry and the quality of our ‘Yakju’ by the quality uniformity of solid starter manufacture using the brewing fungus with having good enzyme activity.

Natural Occurrence of Aflatoxigenic &lt;i&gt;Aspergillus&lt;/i&gt; Species and Aflatoxins in Traditional Korean Fermentation Starters, &lt;i&gt;Meju&lt;/i&gt; and &lt;i&gt;Nuruk&lt;/i&gt;

Meju and nuruk (respectively soybean and malt) are traditional Korean fermentation starters that are vulnerable to contamination by harmful microorganisms such as aflatoxigenic fungi and their associated aflatoxins (AFs). In this study, Aspergillus spp. were isolated and identified from a total of 57 meju and 18 nuruk samples collected from Korean markets. Their potential aflatoxigenicity was investigated by examining the presence of three aflatoxin biosynthetic genes (aflO, aflP, and aflR) using multiplex polymerase chain reaction (mPCR) assays. Thereafter, aflatoxin production of isolates and the natural occurrence of AFs in meju and nuruk samples were analyzed by high-performance liquid chromatography (HPLC). A total of 177 Aspergillus isolates were identified and 130 isolates were obtained from meju samples. Of these, 25 isolates (19.2%) contained all three aflatoxin biosynthetic genes, and five (20%) of these isolates produced aflatoxins. Forty-seven of the Aspergillus isolates were obtained from nuruk samples, five of which (10.6%) expressed all three AF biosynthetic genes; however, none of these strains produced AFs. HPLC analysis showed that 88% (51/58) of the meju samples and 39% (7/18) of nuruk samples were not contaminated with AFs (below limit of detection). Among the isolates isolated from meju and nuruk, there were aflatoxigenic strains containing all three aflatoxin biosynthetic genes or producing aflatoxin in medium, but the frequency of aflatoxin contamination was low in the meju and nuruk samples.

Evaluation of bacterial diversity during fermentation process: a comparison between handmade and machine-made high-temperature Daqu of Maotai-flavor liquor

PurposeHigh-temperature Daqu is a traditional fermentation starter that is used for Chinese Maotai-flavor Baijiu production. Although the bacteria in high-temperature Daqu are known to be responsible for developing the quality and flavor of Baijiu during the fermentation process, there is little information on the properties of the bacteria during the fermentation of high-temperature Daqu, especially machine-made high-temperature Daqu. This has limited the development of the Maotai-flavor Baijiu industry, particularly with regard to the mechanized production of Maotai-flavor Baijiu.MethodsIllumina MiSeq high-throughput sequencing was applied to study bacterial compositions during the fermentation of handmade and machine-made high temperatures.ResultsThe results show that bacterial diversity in machine-made Daqu was similar but higher than that in handmade Daqu at the end of fermentation, and there was no significant difference between the methods with regard to the dominant genera and their dynamic changes during fermentation. Rhizobium, Bacillus, Thermoactinomyces, Weissella, Lactobacillus, and Saccharopolyspora were the dominant genera during the fermentation of both Daqus, although the relative abundance of these dominant genera differed between the two methods. Interestingly, the machine-made Daqu contained a higher relative abundance of Bacillus than handmade Daqu at all fermentation times. Bacillus is the most important functional bacteria in the fermentation of Maotai-flavor Baijiu, suggesting that mechanical-molding methods could be applied to industrial Maotai-flavor Daqu production.ConclusionThese results suggest that mechanical-molding methods could be applied to industrial Maotai-flavor Daqu production, which could be helpful for industrial Maotai-flavor Baijiu production and the development of fermentation technology.

Chinese Yellow Rice Wine Processing with Reduced Ethyl Carbamate Formation by Deleting Transcriptional Regulator Dal80p in Saccharomyces cerevisiae.

Ethyl carbamate (EC) is a potential carcinogen that forms spontaneously during Chinese rice wine fermentation. The primary precursor for EC formation is urea, which originates from both external sources and arginine degradation. Urea degradation is suppressed by nitrogen catabolite repression (NCR) in Saccharomyces cerevisiae. The regulation of NCR is mediated by two positive regulators (Gln3p, Gat1p/Nil1p) and two negative regulators (Dal80p/Uga43p, Deh1p/Nil2p/GZF3p). DAL80 revealed higher transcriptional level when yeast cells were cultivated under nitrogen-limited conditions. In this study, when DAL80-deleted yeast cells were compared to wild-type BY4741 cells, less urea was accumulated, and genes involved in urea utilization were up-regulated. Furthermore, Chinese rice wine fermentation was conducted using dal80Δ cells; the concentrations of urea and EC were both reduced when compared to the BY4741 and traditional fermentation starter. The findings of this work indicated Dal80p is involved in EC formation possibly through regulating urea metabolism and may be used as the potential target for EC reduction.