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Sake (Japanese rice wine) was fermented in pottery for more than a millennium before wooden barrels were adopted to obtain a greater brewing capacity. Although a recently conducted analysis of sake brewed in pottery indicated that sake brewed in unglazed pottery contains more ethanol than that brewed in glazed pottery, little is known about the characteristics of sake brewed in pottery. In this study, we used two types of ceramic containers of identical size, one glazed and one unglazed, for small-scale sake brewing to evaluate the effects of glazing on fermentation properties. The following parameters were measured continuously in the sake samples over 3 weeks of fermentation: temperature, weight, ethanol concentration, and glucose concentration in sake mash. Taste-sensory values, minerals, and volatile components were also quantified in the final fermented sake mash. The results show that, in the unglazed containers, the temperature of the sake mash was lower and the weight loss was higher compared to the sake mash in the glazed containers. The quantity of ethanol and the levels of Na+, Fe3+, and Al3+ tended to be higher in the sake brewed in the unglazed pottery. A taste-sensory analysis revealed that umami and saltiness were also higher in the samples brewed in the unglazed pottery. These results suggest that glazing affects multiple fermentation parameters and the flavor of sake brewed in pottery. They may also suggest that the materials of the containers used in sake brewing generally affect the fermentation properties. [ABSTRACT FROM AUTHOR]

In the traditional (kimoto) method of sake (Japanese rice wine) brewing, Saccharomyces cerevisiae yeast cells are exposed to lactate, which is produced by lactic acid bacteria in the seed mash. Lactate promotes the appearance of glucose‐repression‐resistant [GAR+] cells. Herein, we compared the resistance to glucose repression among kimoto, industrial, and laboratory yeast strains. We observed that the frequencies of the spontaneous emergence of [GAR+] cells among the kimoto strains were higher than those among the industrial and laboratory strains. The fermentation ability of a kimoto yeast (strain U44) was lower than that of an industrial strain (K701), as [GAR+] cells generally showed slower ethanol production. The addition of lactate decreased the fermentation abilities of the K701 strain by increasing the number of [GAR+] cells, but it did not affect those of the U44 strain. These results suggest that lactate controlled fermentation by promoting the appearance of [GAR+] cells in the industrial sake strains but not in the kimoto strains. Take‐away: Yeasts isolated from sake lees (paste) used in traditional kimoto‐style brewing were compared with industrial sake yeasts.Glucose‐repression‐resistant [GAR+] cells were detected at high frequency in the kimoto yeast strains.Lactate strongly promoted the emergence of [GAR+] cells in both kimoto and industrial sake yeasts.Lactate downregulated the fermentation efficiency in industrial sake yeast but not kimoto yeast.The ratio of [GAR+] cells in yeasts may affect the yeasts' fermentation properties. [ABSTRACT FROM AUTHOR]

The emergence and spread of mutants resistant to bacteriocins would threaten the safety of using bacteriocins as food preservatives. To determine the physiological characteristics of resistant mutants, mutants of Enterococcus faecium resistant to mundticin KS, a class IIa bacteriocin, were isolated. Two types of mutant were found that had different sensitivities to other antimicrobial agents such as nisin (class I) and kanamycin. Both mutants were resistant to mundticin KS even in the absence of M[g.sup.2+] ions. The composition of unsaturated fatty acids in the resistant mutants was significantly increased in the presence of mundticin KS. The composition of the phospholipids in the two resistant mutants also differed from those in the wild-type strain. The putative zwitterionic amino-containing phospholipid in both mutants significantly increased, whereas amounts of phosphatidylglycerol and cardiolipin decreased. These changes in membrane structure may influence resistance of enterococci to class IIa and class I bacteriocins.

Research demonstrates that yeast cells devoid of arginase encoding gene, CAR1, accumulate arginine and/or glutamate, which enhance leavening of the frozen-dough, indicating that intracellular accumulation of charged amino acids lead to freeze tolerance in doughs.

Research has been conducted on the bacteriocin mundticin KS, an antilisterial peptide produced by Enterococcus mundii NFRI 7393. The characterization of this peptide belonging to the class IIa bacteriocins has been carried out and the results indicate that mundticin KS has been described by purified peptide N-terminal sequencing and mundticin gene cluster sequencing.

A study has revealed that trehalose accumulation may be the critical determinant in stress tolerance in Saccharomyces cerevisae. An experiment involving trehalose accumulation was conducted. This was done through the use of the gene disruption method on diploid homozygous neutral trehalon mutants found in commercial yeast strains. The process was meant to regulate trehalose cellular levels through the avoidance of hydrolyzing enzymes. The trehalose mutations were able to suppress intracellular trehalose degradation and significantly improve freeze tolerance during the fermentation process.

An enrichment culture technique was employed in extracting a deoxynivalenol metabolizing mixed microbial culture from soil samples. The strain E3-39, which belongs to the Agrobacterium-Rhizobium group, was isolated from the enrichment culture. Two minor and one major deoxynivalenol metabolite was observed in the e3-39 culture filtrates' ethyl acetate extracts. The bacterium was also found capable of metabolizing 3-acetyldeoxynivalenol but not fusarenon-x and nivalenol.

A strain of Streptomyces lividans, TK24, was observed to produce a pigmented antibiotic, actinorhodin, although S. lividans does not usually produce this antibiotic. Genetic analysis showed that a streptomycin-resistant mutation str-6 in strain TK24 is responsible for induction of antibiotic synthesis. Findings revealed that the onset and extent of secondary metabolism in Streptomyces spp. is significantly regulated by the translational mechanism.

Sporulation through ADP-ribosylation of certain functional proteins is controlled by a sporulation gene. ADP-ribosylated protein profile is modified during sporulation. A number of mutants resistant to 3-methoxybenzamide, an ADP-ribosyltransferase inhibitor, fail to ADP-ribosylate 36- and 58-kDa proteins during sporulation and antibiotic production. ADP-ribosylation of 36-kDa protein can be activated by decoyinine treatment and amino acid limitation.

The ADP-ribosyltransferase activity and ADP-ribosylated proteins are different in wild type Streptomyces coelicolor A3(2) cells and mutants resistant to 3-aminobenzamide, an ADP-ribosyltransferase suppressor. The 39, 41, 43 amd 46 kDa ADP-ribosylated proteins appear during the start of differentiation in the wild-type cells while a 92 kDa protein disappears. The mutants contain the 92 kDa protein while the other proteins are absent during differentiation. The mutants form no aerial mycelium and antibiotics. The mutation is located at the brgA locus near the uraA locus.

Abstract Background Reproduction and sustainability are important for future society, and bioprocesses are one technology that can be used to realize these concepts. However, there is still limited variation in bioprocesses and there are several challenges, especially in the operation of energy-requiring bioprocesses. As an example of a microbial platform for an energy-requiring bioprocess, we established a process that efficiently and enzymatically synthesizes 2′-deoxyribonucleoside from glucose, acetaldehyde, and a nucleobase. This method consists of the coupling reactions of the reversible nucleoside degradation pathway and energy generation through the yeast glycolytic pathway. Results Using E. coli that co-express deoxyriboaldolase and phosphopentomutase, a high amount of 2′-deoxyribonucleoside was produced with efficient energy transfer under phosphate-limiting reaction conditions. Keeping the nucleobase concentration low and the mixture at a low reaction temperature increased the yield of 2′-deoxyribonucleoside relative to the amount of added nucleobase, indicating that energy was efficiently generated from glucose via the yeast glycolytic pathway under these reaction conditions. Using a one-pot reaction in which small amounts of adenine, adenosine, and acetone-dried yeast were fed into the reaction, 75 mM of 2′-deoxyinosine, the deaminated product of 2′-deoxyadenosine, was produced from glucose (600 mM), acetaldehyde (250 mM), adenine (70 mM), and adenosine (20 mM) with a high yield relative to the total base moiety input (83%). Moreover, a variety of natural dNSs were further synthesized by introducing a base-exchange reaction into the process. Conclusion A critical common issue in energy-requiring bioprocess is fine control of phosphate concentration. We tried to resolve this problem, and provide the convenient recipe for establishment of energy-requiring bioprocesses. It is anticipated that the commercial demand for dNSs, which are primary metabolites that accumulate at very low levels in the metabolic pool, will grow. The development of an efficient production method for these compounds will have a great impact in both fields of applied microbiology and industry and will also serve as a good example of a microbial platform for energy-requiring bioprocesses.

Abstract Background During the bread-making process, industrial baker's yeast, mostly Saccharomyces cerevisiae, is exposed to baking-associated stresses, such as air-drying and freeze-thaw stress. These baking-associated stresses exert severe injury to yeast cells, mainly due to the generation of reactive oxygen species (ROS), leading to cell death and reduced fermentation ability. Thus, there is a great need for a baker's yeast strain with higher tolerance to baking-associated stresses. Recently, we revealed a novel antioxidative mechanism in a laboratory yeast strain that is involved in stress-induced nitric oxide (NO) synthesis from proline via proline oxidase Put1 and N-acetyltransferase Mpr1. We also found that expression of the proline-feedback inhibition-less sensitive mutant γ-glutamyl kinase (Pro1-I150T) and the thermostable mutant Mpr1-F65L resulted in an enhanced fermentation ability of baker's yeast in bread dough after freeze-thaw stress and air-drying stress, respectively. However, baker's yeast strains with high fermentation ability under multiple baking-associated stresses have not yet been developed. Results We constructed a self-cloned diploid baker's yeast strain with enhanced proline and NO synthesis by expressing Pro1-I150T and Mpr1-F65L in the presence of functional Put1. The engineered strain increased the intracellular NO level in response to air-drying stress, and the strain was tolerant not only to oxidative stress but also to both air-drying and freeze-thaw stresses probably due to the reduced intracellular ROS level. We also showed that the resultant strain retained higher leavening activity in bread dough after air-drying and freeze-thaw stress than that of the wild-type strain. On the other hand, enhanced stress tolerance and fermentation ability did not occur in the put1-deficient strain. This result suggests that NO is synthesized in baker's yeast from proline in response to oxidative stresses that induce ROS generation and that increased NO plays an important role in baking-associated stress tolerance. Conclusions In this work, we clarified the importance of Put1- and Mpr1-mediated NO generation from proline to the baking-associated stress tolerance in industrial baker's yeast. We also demonstrated that baker's yeast that enhances the proline and NO synthetic pathway by expressing the Pro1-I150T and Mpr1-F65L variants showed improved fermentation ability under multiple baking-associated stress conditions. From a biotechnological perspective, the enhancement of proline and NO synthesis could be promising for breeding novel baker's yeast strains.

Abstract Background Lignocellulosic materials are abundant and among the most important potential sources for bioethanol production. Although the pretreatment of lignocellulose is necessary for efficient saccharification and fermentation, numerous by-products, including furan derivatives, weak acids, and phenolic compounds, are generated in the pretreatment step. Many of these components inhibit the growth and fermentation of yeast. In particular, vanillin is one of the most effective inhibitors in lignocellulose hydrolysates because it inhibits fermentation at very low concentrations. To identify the genes required for tolerance to vanillin, we screened a set of diploid yeast deletion mutants, which are powerful tools for clarifying the function of particular genes. Results Seventy-six deletion mutants were identified as vanillin-sensitive mutants. The numerous deleted genes in the vanillin-sensitive mutants were classified under the functional categories for 'chromatin remodeling' and 'vesicle transport', suggesting that these functions are important for vanillin tolerance. The cross-sensitivity of the vanillin-sensitive mutants to furan derivatives, weak acids, and phenolic compounds was also examined. Genes for ergosterol biosynthesis were required for tolerance to all inhibitory compounds tested, suggesting that ergosterol is a key component of tolerance to various inhibitors. Conclusion Our analysis predicts that vanillin tolerance in Saccharomyces cerevisiae is affected by various complicated processes that take place on both the molecular and the cellular level. In addition, the ergosterol biosynthetic process is important for achieving a tolerance to various inhibitors. Our findings provide a biotechnological basis for the molecular engineering as well as for screening of more robust yeast strains that may potentially be useful in bioethanol fermentation.