Lactobacilus nuruki sp. nov., isolated from Nuruk, a Korean fermentation starter.

A rod-shaped, Gram-stain-positive, non-flagellated, facultatively anaerobic bacterium, designated SYF10-1aT, was isolated from Nuruk, a Korean traditional fermentation starter. It grew at 4-40 °C (optimum 37 °C), at pH 3.0-9.0 (optimum, pH 7.0) and with 0-5 % (w/v) NaCl. Phylogenetic analysis using 16S rRNA gene sequences revealed that strain SYF10-1aT belonged to the genus Lactobacillus and showed the highest sequence similarity of 98.7 % to Lactobacillus crustorum LMG 23699T. A comparison of two housekeeping genes, pheS and rpoA, supported the suggestion that strain SYF10-1aT fell within the radius of the genus Lactobacillus, but was clearly separated from its closest related species. The average nucleotide identity value and digital DNA-DNA hybridization value between strain SYF10-1aT and the most closely related species,L. crustorum LMG 23699T, were 80.5 and 33.3 %, respectively. The predominant cellular fatty acids were C16 : 0, C18 : 1ω9c, C18 : 1ω7c and summed feature 3 (including iso-C15 : 0 2-OH and/or C16 : 1ω7c). Polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two unidentified aminolipids and two unidentified glycolipids. The cell-wall peptidoglycan was of the A4α type with an interpeptide bridge comprising l-Lys-d-Asp. The DNA G+C content was 34.2 mol%. On the basis of this taxonomic study, strain SYF10-1aT represents a novel species within the genus Lactobacillus, for which the name Lactobacillus nuruki sp. nov. is proposed. The type strain is SYF10-1aT (=KACC 18726T=NBRC 112011T).

Antimelanogenic Effects of Polygonum tinctorium Flower Extract from Traditional Jeju Fermentation via Upregulation of Extracellular Signal-Regulated Kinase and Protein Kinase B Activation.

This study was carried out to investigate the antimelanogenic effects of a Polygonum tinctorium flower extract obtained using red nuruk, a traditional Jeju barley-based fermentation starter. We also studied the mechanism of action of the P. tinctorium fermented flower extract (PTFFE) in mouse melanoma cells (B16F10). Cells were treated with various concentrations (62.5, 125 and 250 µg/mL) of PTFFE and the results showed that PTFFE significantly decreased the melanin content and tyrosinase activity without being cytotoxic. In addition, PTFFE strongly inhibited the expression of tyrosinase and tyrosinase-related protein 2 by decreasing the expression of the microphthalmia-associated transcription factor, as shown by a western blot assay. Furthermore, PTFFE inhibited melanogenesis via upregulation of the phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B, also known as AKT. We also used inhibitors such as PD98059 (a specific ERK inhibitor) or LY294002 (an AKT inhibitor) to determine whether the signaling pathways are involved. High-performance liquid chromatography fingerprinting showed the presence of a quercetin glucoside (isoquercitrin) and quercetin in PTFFE. To test the potential for PTFFE application as a cosmetic material, we also performed a primary skin irritation test on human skin. In this assay, PTFFE did not induce any adverse reactions at the treatment dose. Based on these results, we suggest that PTFFE may be considered a potential antimelanogenesis candidate for topical applications.

Bioformation of Volatile and Nonvolatile Metabolites by Saccharomycopsis fibuligera KJJ81 Cultivated under Different Conditions-Carbon Sources and Cultivation Times.

Saccharomycopsis fibuligera KJJ81 isolated from nuruk is an amylolytic yeast that is widely used as a microbial starter in various fermented foods. Volatile and nonvolatile metabolites of S. fibuligera KJJ81 were investigated according to different carbon sources and cultivation times using a nontargeted metabolomic approach. Partial-least-squares discriminant analysis was applied to determine the major metabolites, which were found to be closely related to the clustering and discrimination of S. fibuligera KJJ81 samples. Some volatile metabolites derived from phenylalanine, such as 2-phenylethanol, 2-phenylethyl acetate, and ethyl phenylacetate, were predominantly found in cultivation medium containing glucose (YPD medium). In addition, the level of 2-phenylethanol increased continuously with the cultivation time. In terms of nonvolatile metabolites, carbohydrates (mannose, arabitol, and mannitol), fatty acids (palmitic acid and stearic acid), organic acids (oxalic acid and succinic acid), and amino acids (isoleucine, serine, alanine, glutamic acid, glycine, proline, phenylalanine, and threonine) were the main contributors to S. fibuligera KJJ81 samples cultivated in YPD medium according to cultivation time. These results show that the formation of volatile and nonvolatile metabolites of S. fibuligera KJJ81 can be significantly affected by both the carbon sources and the cultivation time.

Effects of initial moisture content of Korean traditional wheat-based fermentation starter nuruk on microbial abundance and diversity.

The brewing of makgeolli, one of Korea's most popular alcoholic beverages that is gaining popularity globally, is facilitated by nuruk, a traditional Korean cereal starter. The nuruk microbiome greatly influences the fermentation process as well as the nutritional, hygienic, and aromatic qualities of the product. This study is a continuation of our efforts to examine nuruk biodiversity at a depth previously unattainable. In this study, microfloral dynamics in wheat-based nuruk C, composed of traditional ingredients such as barley, green gram, and wheat and fermented under various internal moisture contents of 20% (C20), 26% (C26), and 30% (C30), was evaluated using 454 pyrosequencing during the 30-day fermentation process. Rarefaction analysis and alpha diversity parameters indicated adequate sampling. C20 showed the greatest fungal richness and diversity, C20 and C26 exhibited similar bacterial richness and diversity, while C30 had low fungal and bacterial richness. Fungal taxonomic assignments revealed that the initial moisture content caused selective enrichment of Aspergillus candidus with a decreasing trend during fermentation, whereas Saccharomycetales sp. exhibited increasing relative abundance with increasing moisture content from day 6 of the fermentation process. Depending on initial moisture level, changes in bacterial communities were also observed in the genera Streptomyces, Bacillus, and Staphylococcus, with decreasing trends whereas Saccharopolyspora exhibited a sigmoidal trend with the highest abundance in C26. These findings demonstrate the possible impact of initial moisture content of nuruk on microfloral richness, diversity, and dynamics; this study is thus a step toward our ultimate goal of enhancing the quality of nuruk.

Metagenomic analysis of fungal diversity in Korean traditional wheat-based fermentation starter nuruk.

Nuruk, a traditional natural starter, is extensively used in the brewing of Makgeolli, one of Korea's most popular alcoholic beverages that has been recently gaining global popularity. Thus, the quality of traditional nuruk needs to be enhanced. The nuruk mycobiome greatly influences both fermentation process as well as palatability enhancement. Limitations of culture-dependent identification restrict an accurate analysis of fungal diversity and distribution in nuruks. 454 pyrosequencing of two traditional wheat-based nuruks, prepared at two representative temperature conditions revealed a total of 153 and 53 OTUs for nuruks A and B, respectively, from a total of 33,157 ITS sequences. Phylogenetic assignments indicated that nuruk A mycobiota was dominated by the genera Aspergillus and Mucorales, whereas nuruk B by Rhizomucor. Species-level identification indicated that Mucorales sp., Aspergillus candidus, and Aspergillus cibarius predominated in nuruk A mycoflora whereas Rhizomucor pusillus, Mucorales sp., and Thermoascus crustaceus in nuruk B. The alpha diversity indices suggest nuruk A mycobiota to be more diverse than that of nuruk B at almost all time points of fermentation. Resemblances of patterns of predominant species composition and succession between culture-dependent and -independent phylogenetic analysis creates the potential to reconstruct the nuruk mycobiome in vitro, which allows the establishment of a standard inoculum for scientific comparison.

Enzymatic Hydrolysis of Tenebrio molitor (Mealworm) Using Nuruk Extract Concentrate and an Evaluation of Its Nutritional, Functional, and Sensory Properties.

Enzymatic protein hydrolysis is a well-established method for improving the quality of dietary proteins, including edible insects. Finding effective enzymes from natural sources is becoming increasingly important. This study used nuruk extract concentrate (NEC), an enzyme-rich fermentation starter, to produce protein hydrolysate from defatted Tenebrio molitor (also called mealworm, MW). The nutritional, functional, and sensorial properties of the hydrolysate were then compared to those obtained using commercial proteases (alcalase and flavourzyme). The protease activities of the crude nuruk extract (CNE), NEC, alcalase, and flavourzyme were 6.78, 12.71, 11.07, and 12.45 units/mL, respectively. The degree of hydrolysis and yield of MW hydrolysis by NEC were 15.10 and 35.92% (w/w), respectively. MW hydrolysate was obtained using NEC and had a significantly higher free amino acid content (90.37 mg/g) than alcalase (53.01 mg/g) and flavourzyme (79.64 mg/g) hydrolysates. Furthermore, the NEC hydrolysis of MW increased the antioxidant and angiotensin-converting enzyme inhibitory activity, with IC50 values of 3.07 and 0.15 mg/mL, respectively. The enzymatic hydrolysis also improved sensory properties, including umaminess, sweetness, and saltiness. Overall, this study found that the NEC hydrolysis of MW outperformed commercial proteases regarding nutritional quality, sensory attributes, and biological activity. Therefore, nuruk could potentially replace commercial proteases, lowering the cost of enzymatic protein hydrolysis.

Effects of saccharification agents on the microbial and metabolic profiles of Korean rice wine (makgeolli).

To brew rice wine, a saccharification agent is critical to provide sugars necessary for yeast to ferment alcohol. Nuruk, a traditional Korean saccharification agent, contains saccharification enzymes and various microorganisms, including fungi and lactic acid bacteria (LAB). To investigate the effect of saccharification agents on Korean rice wine (makgeolli), we analyzed makgeolli brewed with different saccharification agents, such as koji and nuruk. In contrast to koji makgeolli, nuruk makgeolli had a distinct microbial profile with higher proportion of LAB. Comparing the microbial profiles of the saccharification agents and makgeolli revealed that the dominant microorganisms in the makgeolli were possibly derived from the saccharification agents. Several metabolites also exhibited distinct profiles depending on the saccharification agent generating the total metabolic profile difference of makgeolli samples. Collectively, the saccharification agent could provide dominant microorganisms in the makgeolli microbiota, leading to a distinct microbial and metabolic profile of makgeolli depending on its type.

Characterisation of Korean rice wine (makgeolli) prepared by different processing methods.

Four methods of preparing makgeolli, a traditional Korean turbid rice wine, were reported in this study. The four processing routes include single-stage simultaneous saccharification and fermentation of glutinous rice with nuruk - a Korean starter culture (1SF-N), single-stage fermentation with nuruk and yeast (1SF-YN), two-stage fermentation (2SF) and three-stage fermentation (3SF). Chemical analysis was used to determine how the different processing routes could affect the rice wine's properties in terms of alcohol content, pH, colour, mineral content, proximate composition, antioxidant activity, total phenolic content, sugar, free amino acid, and organic acid profile. Sensory analysis using polarised projective mapping (PPM) and 62 participants found that sweetness is the most desirable attribute for makgeolli among New Zealand consumers with sourness and bitterness as less desirable. The 2SF makgeolli sample had the highest concentration of glucose (8.2 mg/mL) and maltose (107 mg/mL) and in the PPM experiment was the most preferred out of the four processing methods. The 1SF-N makgeolli sample had the highest alcohol (13% ABV), crude protein (4.9%), antioxidant activity, total phenolic (621 mg GAE/L) and free amino acids content, however, it was the least overall liked makgeolli sample. Overall, the novelty of this research includes formulating a traditional Korean turbid rice wine in a Western country environment and evaluating consumer perception of makgeolli beyond the normal clientele in South Korea. From these results it is suggested that the properties of makgeolli can be manipulated via processing to suit the brewer's sensory needs that best fits the consumer market.

Stachydrine derived from fermented rice prevents diet-induced obesity by regulating adipsin and endoplasmic reticulum homeostasis.

Makgeolli, a widely consumed traditional alcoholic beverage in Korea, is brewed mainly from rice using Nuruk as a fermentation starter, which contains fungi, yeast, and lactic acid bacteria. Among 58 Makgeolli samples brewed using various Nuruks, we found that one exhibited anti-obesity properties, with stachydrine shown to be responsible for these properties. Stachydrine promotes lipolysis and inhibits lipid accumulation in 3T3-L1 adipocytes; it also reduces weight gain and improves glucose tolerance and insulin resistance in a mouse model. Stachydrine dramatically suppresses adipsin mRNA levels in liver and adipose tissue, whereas serum adipsin levels were elevated in stachydrine-treated mice compared to mice fed a high-fat diet alone. Moreover, stachydrine recovers endoplasmic reticulum homeostasis and regulates adipsin expression. We highlight the potential use of stachydrine as a therapeutic agent for the treatment of obesity and insulin resistance and the use of Makgeolli fermented by Nuruk as a source of novel bioactive compounds.

Draft genome sequence data of multi-stress tolerant yeast Millerozyma farinosa KCTC27753 isolated from nuruk.

The strain Millerozyma farinosa KCTC27753, isolated from nuruk, is a multi-stress tolerant yeast which grows at 46 °C temperature and pH 3.0. This strain can withstand fermentation inhibitors, such as furfural and phenolic compounds released from biomass. Hence, this strain could be used for bioethanol production. The draft genome sequence of M. farinosa KCTC27753 was analyzed by PacBio RSII. The genome length is 21,255,474 bp and it consists of 17 contigs. The GC content of the genome is 41.1%. The genome analysis identified a total of 10,910 plausible gene-coding regions in this strain.

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-1ß, transforming growth factor-ß, 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.

Anti-Osteoporosis Effects of the Eleutherococcus senticosus, Achyranthes japonica, and Atractylodes japonica Mixed Extract Fermented with Nuruk.

Vigeo is a mixture of fermented extracts of Eleutherococcus senticosus Maxim (ESM), Achyranthes japonica (Miq.) Nakai (AJN), and Atractylodes japonica Koidzumi (AJK) manufactured using the traditional Korean nuruk fermentation method. Although the bioactive effects of ESM, AJN, and AJK have already been reported, the pharmacological effects of Vigeo have not been proven. Therefore, in this study, we investigated whether Vigeo had inhivitory effects on lipopolysaccharide (LPS)-induced inflammatory bone loss in vivo and receptor activator of nuclear factor-B ligand (RANKL)-induced osteoclastogenesis and the related mechanism in vitro. Vigeo administration conferred effective protection against bone loss induced by excessive inflammatory response and activity of osteoclasts in LPS-induced inflammatory osteoporosis mouse model. In addition, Vigeo significantly suppressed the formation of tartrate-resistant acid phosphatase-positive osteoclasts induced by RANKL and inhibited F-actin formation and bone resorbing activity without any cytotoxicity. Moreover, Vigeo significantly inhibited RANKL-induced phosphorylation of p38, ERK, JNK, IκB, and AKT and degradation of IkB. Additionally, Vigeo strongly inhibited the mRNA and protein expression of c-FOS and NFATc1 and subsequently attenuated the expression of osteoclast specific marker genes induced by RANKL. We demonstrated for the first time the anti-osteoporosis effect of Vigeo, suggesting that it could be a potential therapeutic candidate for the treatment of osteoclast-mediated inflammatory bone diseases.

Draft genome sequence data of the starch-utilizing yeast Saccharomycopsis fibuligera MBY1320 isolated from Nuruk.

Saccharomycopsis fibuligera MBY1320 was isolated from Nuruk, a traditional Korean starter for makgeolli (rice wine) production. This isolate has previously been reported to exhibit thermotolerance and starch-degrading activities. In this data description, we present the draft genome sequence of S. fibuligera MBY1320. The genome contained 19,138,941 bp in 16 contigs, and the internal transcribed spacer region of S. fibuligera MBY1320 rRNA gene showed the highest similarity with that of S. fibuligera NRRL Y-2388. The BioProject sequence has been deposited at DDBJ/EMBL/GenBank and Mendeley database. The GenBank accession numbers are PRJNA598085 for the BioProject data, SAMN13698230 for the BioSample data, and GCA_012062855 for the GenBank data.

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.

Influence of aflatoxin in Nuruk on the safety of starch-based alcoholic beverage.

Nuruk is a fermentation agent used to manufacture alcoholic beverages, which contains a variety of microorganisms. Most microorganisms in Nuruk are useful for the production of alcoholic beverages; however, Nuruk can be infected with Aspergillus flavus, which produces aflatoxin (AF). Therefore, this study analyzed total AF concentrations in Nuruk, the transfer of AF from Nuruk to alcoholic beverages, and AF-producing microorganisms to determine the safety of alcoholic beverages with respect to this toxin. ELISA showed that total AF levels in 14 of 61 Nuruk samples exceeded 15 ppb, the Korean permissible level in cereal products. In alcoholic beverages produced with Nuruk containing AF levels >15 ppb, only AF G1 was detected, at a level of 0.3 ppb, and the transfer ratio of AF G1 was approximately 1.2% to 1.3%. The dominant genera in Nuruk were Aspergillus and Rhizopus. Among 30 strains belonging to Aspergillus, 10 produced only AF B1 at levels of 0.1 to 2.4 ppb after incubation at 25 °C for 8 days on potato dextrose agar plates. Although AF in Nuruk was rarely transferred to alcoholic beverages and the aflatoxigenic strains were found to possess poor AF-producing capacity, further efforts to reduce AF in Nuruk are needed to ensure the safety of alcoholic beverages.

Alteration of gut microbiota composition by short-term low-dose alcohol intake is restored by fermented rice liquor in mice.

Excessive alcohol consumption can increase gut permeability and alter the gut bacterial communities, influencing the pathogenesis of several disorders including alcoholic liver disease, endotoxemia, and systemic inflammation. Although recent studies have highlighted a pivotal role for gut microbiota in alcohol metabolism and alcoholic liver injury, the results have primarily been obtained from binge models treated with physiologically acute dose of alcohol. We sought to investigate the effect of low-dose (0.8 g/kg/day) and short-term (one week) consumption of alcohol on changes in gut microbiota composition in mice. The low-dose consumption of alcohol immediately altered fecal microbiota composition in mice after 1 and 7 days of treatment. We also evaluated the influence of alcoholic beverages containing various microbes using fermented rice liquors (FRLs, called Makgeolli in Korea) on gut microbiota and systemic inflammation. One week of FRLs consumption restored fecal microbiota compositions altered by alcohol administration in mice, with the abundance of Bacteroidetes and Firmicutes phyla recovered to levels of the control group. In addition, mice receiving FRLs exhibited increased fecal production of short-chain fatty acids (SCFA) such as butyric acid and propionic acid within 7 days, and reduced inflammatory responses induced by alcohol administration in the serum and colon. Taken together, these results suggest that short-term and low-dose alcohol intake induces alterations in fecal microbiota composition, and FRLs administration can restore microbial composition and suppress intestinal inflammation, highlighting potential benefits of FRLs as fermented foods.

Effect of heat-treated Nuruk on the quality characteristics of aged Yakju.

Long-term aging of Yakju, a traditional Korean liquor made of rice and Nuruk (a fermentation agent), causes browning and odor and flavor development. This study investigated the effects of heat-treated Nuruk (50-80 °C, 30 min) on Yakju quality. The saccharogenic powers and glucoamylase, α-amylase, and carboxypeptidase activities were similar in non-heat-treated Nuruk and that treated at 50 °C. However, acidic protease and alcohol dehydrogenase decreased above 50 °C. The content of nitrogen-containing compounds was inversely proportional to the heat-treatment temperature. Compounds that cause off-flavors decreased at 50-60 °C, but increased at 70-80 °C, whereas compounds that provide fragrance increased at 50-60 °C. Sensory evaluation indicated that bad taste attributes were higher in Yakju produced using non-heat-treated Nuruk. Therefore, heat treatment of Nuruk at 50 °C can be adopted as a method for improving Yakju quality, as enzymatic activities that affect color, aroma, and taste are regulated.

Penicillin Binding Protein from Pediococcus acidilactici Isolated from Nuruk for Food Biopreservative.

BACKGROUND: Korean traditional nuruk, consisting of a variety of microorganisms, is widely used in traditional liquor materials. The present study evaluated the antimicrobial activity of strains isolated from Korean traditional nuruk in 2016. METHODS: The strain was isolated from Korea traditional nuruk and performed antimicrobial activities using the paper disc test and phylogenetic analysis using 16S rRNA sequencing. The bacteriocin was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. RESULTS: The isolate, S-2, demonstrated highest antibacterial activity against various gram-positive and gram-negative pathogens, including Klebsiella pneumoniae, Salmonella enterica subsp. enterica, Bacillus subtilis, B. cereus, Escherichia coli and Shigella flexneri. The isolated was identified as P. acidilactici, by 16S rRNA sequence analysis. Antibacterial activity of P. acidilactici was retained over a wide temperature range. And the P. acidilactici strains remained active over a wide pH range. However, reduced activities were obtained at alkaline pH. When the bacteriocins from this strain were treated with proteolytic enzymes, loss of antibacterial activity was observed. No effect in the activity, however, was observed upon treatment with α-amylase, ß-amylase, lipases, proteases, and proteinase K. The molecular weight of bacteriocins was estimated to be approximately 51 kDa. Using MALDITOF/MS, the bacteriocins were identified as a putative penicillin binding protein. CONCLUSION: This study is the first report of isolation of bacteriocin with the above mode of actions from Korean traditional nuruk. The bacteriocins produced by the strain have potential applications in food preservation.

Characteristics of Korean Alcoholic Beverages Produced by Using Rice Nuruks Containing Aspergillus oryzae N159-1.

Herein, nuruks derived from non-glutinous and glutinous rice inoculated with Aspergillus oryzae N159-1 (having high alpha-amylase and beta-glucosidase activities) were used to produce Korean alcoholic beverages. The resultant beverages had enhanced fruity (ethyl caproate and isoamyl alcohol) and rose (2-phenethyl acetate and phenethyl alcohol) flavors and high taste scores.

Isolation of thermotolerant yeast Pichia kudriavzevii from nuruk.

Thermotolerant yeast strains were isolated from nuruk, a traditional Korean fermentation starter in which variety of microorganisms are present. Among the isolates, the MBY1358 identified as yeast Pichia kudriavzevii showed significantly higher growth rate (0.59 ± 0.00 1/h) at 44 °C than other strains. Maximum ethanol concentration of 8.35 ± 0.03 g/L was obtained from 20 g/L glucose with yield of 0.44 ± 0.01 g/g at 44 °C, which is 1.14 times ethanol production of the control strain of P. kudriavzevii. The MBY1358, which was significantly more thermotolerant than the control strain and fermented 200 g/L glucose to 107.33 ± 5.03 g/L ethanol at 44 °C, was deposited to Korean Collection for Type Cultures (KCTC) under the accession number 27654.