Sake yeast YHR032W/ERC1 haplotype contributes to high S-adenosylmethionine accumulation in sake yeast strains

Protective effects of Japanese sake yeast on depressive-like behaviors, oxidative stress and inflammatory parameters in a rat model of global cerebral ischemia/reperfusion

Stroke is a serious cerebrovascular disease that causes post-stress depression and death. Stress and inflammation have pivotal roles in the induction of the disease. Several drugs and agents have been used for the treatment of disease, but their uses are faced with limitations owing to their side effects. Natural agents are more efficient for the treatment of stroke due to lower toxicity and their pharmaceutical properties. Sake yeast or Japanese rice wine is an antioxidant compound that could be used to treat stroke and post-stress depression. This study evaluates the effects of sake yeast on depressive-like behaviors, oxidative stress and inflammatory parameters in a rat model of global cerebral ischemia/reperfusion. Rats were divided into four groups, including 1) control: without bilateral common carotid artery occlusion (BCCAO) and sake supplement, 2) Ischemia group: rats induced with BCCAO and lack of therapeutic supplement, and 3 and 4) Ischemia + sake groups: rats induced with BCCAO and treated with 25 and 50 mg/kg sake yeast, respectively. Depressive-like behaviors antioxidant enzymes activities were assessed. The induction of stroke increased oxidant status, inflammatory parameters, and depressive-like behaviors, while the administration of sake could decrease inflammation, depressive-like behaviors, and oxidant status and increase antioxidant enzymes. The yeast could be used as a supplement in combination with other drugs to treat stroke.

Development of sake yeast breeding and analysis of genes related to its various phenotypes

Sake is a traditional Japanese alcoholic beverage made from rice and water, fermented by the filamentous fungi Aspergillus oryzae and the yeast Saccharomyces cerevisiae. Yeast strains, also called sake yeasts, with high alcohol yield and the ability to produce desired flavor compounds in the sake, have been isolated from the environment for more than a century. Furthermore, numerous methods to breed sake yeasts without genetic modification have been developed. The objectives of breeding include increasing the efficiency of production, improving the aroma and taste, enhancing safety, imparting functional properties, and altering the appearance of sake. With the recent development of molecular biology, the suitable sake brewing characteristics in sake yeasts, and the causes of acquisition of additional phenotypes in bred yeasts have been elucidated genetically. This mini-review summarizes the history and lineage of sake yeasts, their genetic characteristics, the major breeding methods used, and molecular biological analysis of the acquired strains. The data in this review on the metabolic mechanisms of sake yeasts and their genetic profiles will enable the development of future strains with superior phenotypes.

Induction of Chromosomal Aneuploids from Brewery Shochu Yeast with Novel Brewery Characteristics

The first development method of brewery shochu yeast focusing on chromosomal aneuploidy is reported in this study. Euploidy diploid shochu yeast S-3 was treated with a microtubule inhibitor, nocodazole, for the purpose of inducing aneuploidy. Next, 2,3,5-triphenyl tetrazolium chloride (TTC) staining and the growth rate were investigated to select aneuploids. Aneuploids were selected at a frequency of 8.2 × 10−4, which was significantly higher than that of the control group, mainly at chromosomes I, II, III, IX, XII, XIII, and XVI. The acquired aneuploids were evaluated for their metabolic and brewing characteristics. A hierarchical cluster analysis based on endogenous metabolite data discriminated euploid S-3 and aneuploids. In addition, principal-component analysis of the constituents of the broth brewed with the strains discriminated between euploid S-3 and aneuploids. Sensory evaluation of the broth brewed with euploid S-3 and aneuploids showed that it tended to differ in aroma and taste. Specific ethanol production rates of the aneuploids were not deteriorated. The method of this selection made it possible to efficiently obtain aneuploids with various brewing characteristics from brewer’s yeast, which do not correspond to genetically modified organisms. This novel breeding method focusing on chromosomal aneuploidy will facilitate the development of novel shochu yeast strains.

Genetic investigation of purine nucleotide imbalance in Saccharomyces cerevisiae

Because metabolism is a complex balanced process involving multiple enzymes, understanding how organisms compensate for transient or permanent metabolic imbalance is a challenging task that can be more easily achieved in simpler unicellular organisms. The metabolic balance results not only from the combination of individual enzymatic properties, regulation of enzyme abundance, but also from the architecture of the metabolic network offering multiple interconversion alternatives. Although metabolic networks are generally highly resilient to perturbations, metabolic imbalance resulting from enzymatic defect and specific environmental conditions can be designed experimentally and studied. Starting with a double amd1 aah1 mutant that severely and conditionally affects yeast growth, we carefully characterized the metabolic shuffle associated with this defect. We established that the GTP decrease resulting in an adenylic/guanylic nucleotide imbalance was responsible for the growth defect. Identification of several gene dosage suppressors revealed that TAT1, encoding an amino acid transporter, is a robust suppressor of the amd1 aah1 growth defect. We show that TAT1 suppression occurs through replenishment of the GTP pool in a process requiring the histidine biosynthesis pathway. Importantly, we establish that a tat1 mutant exhibits synthetic sickness when combined with an amd1 mutant and that both components of this synthetic phenotype can be suppressed by specific gene dosage suppressors. Together our data point to a strong phenotypic connection between amino acid uptake and GTP synthesis, a connection that could open perspectives for future treatment of related human defects, previously reported as etiologically highly conserved.

The sake yeast YHR032W/ERC1 allele contributes to the regulation of the tetrahydrofolate content in the folate synthetic pathway in sake yeast strains

To elucidate the mechanism underlying tetrahydrofolate (THF) accumulation in sake yeast strains compared with that in laboratory yeast strains, we performed a quantitative trait locus (QTL) analysis. The results revealed that the sake yeast ERC1 allele contributes to an increase in the ratio of THF to the total folate content in sake yeast.

Progress in the genomics and genome-wide study of sake yeast

Completion of the whole genome sequence of a laboratory yeast strain Saccharomyces cerevisiae in 1996 ushered in the development of genome-wide experimental tools and accelerated subsequent genetic study of S. cerevisiae. The study of sake yeast also shared the benefit of such tools as DNA microarrays, gene disruption-mutant collections, and others. Moreover, whole genome analysis of representative sake yeast strain Kyokai no. 7 was performed in the late 2000s, and enabled comparative genomics between sake yeast and laboratory yeast, resulting in some notable finding for of sake yeast genetics. Development of next-generation DNA sequencing and bioinformatics also drastically changed the field of the genetics, including for sake yeast. Genomics and the genome-wide study of sake yeast have progressed under these circumstances during the last two decades, and are summarized in this article. Abbreviations: AFLP: amplified fragment length polymorphism; CGH: comparative genomic hybridization; CNV: copy number variation; DMS: dimethyl succinate; DSW: deep sea water; LOH: loss of heterozygosity; NGS: next generation sequencer; QTL: quantitative trait loci; QTN: quantitative trait nucleotide; SAM: S-adenosyl methionine; SNV: single nucleotide variation.

Breeding of a cordycepin-resistant and adenosine kinase-deficient sake yeast strain that accumulates high levels of S-adenosylmethionine

Adenosine kinase (ADO1)-deficient mutants can be obtained from cordycepin-resistant strains, and the disruption of ADO1 causes S-adenosylmethionine (SAM) accumulation. To breed a high-SAM-accumulating yeast strain without genetic manipulation for industrial purposes, we bred a cordycepin-resistant strain using sake yeast kyokai No. 9 as the parent strain with a mutation in adenosine kinase (ADO1) and acquired high-SAM-accumulating strain. In the bred strain (NY9-10), a single mutation (T258I) was present in the ADO1, and this mutation site is an ATP binding site and is highly conserved during evolution. Moreover, it was suggested that high accumulation of SAM and cordycepin resistance in NY9-10 was due to functional deficiency of ADO1 by this mutation. This strain is not a genetically-modified organism and can be employed for use in the food and medicine industry such as mass production and sake making.

Nutritional characterization of sake cake (sake-kasu) after heat-drying and freeze-drying

Sake cake contains rice-derived components, as well as cell components and metabolites of Aspergillus oryzae and Saccharomyces cerevisiae. In this study, the effect of food processing on sake cake (sake-kasu) ingredients was investigated. Sake cake, obtained through brewing liquefied rice, was heat-dried (HD) or freeze-dried (FD) and analyzed. There were no differences in the amounts of proteins, lipids, carbohydrates, vitamin B₆, choline, betaine, nicotinic acid, β-glucan and resistant proteins in HD and FD. There was also no difference in the amount of hydrolyzed amino acids in HD and FD, but many free amino acids were observed in HD. S-adenosyl methionine (SAM) was found to be abundant in FD. Meanwhile, nucleic acid-related components were found to be increased in HD, which seems to be due to the degradation of microbial metabolites. When considering the health benefits of sake cake, it is necessary to pay attention to the effects of processing method. Abbreviations CE-TOFMS: capillary electrophoresis time-of-flight mass spectrometry.

Enhanced S-Adenosylmethionine Production by Increasing ATP Levels in Baker's Yeast ( Saccharomyces cerevisiae)

In the biosynthesis of S-adenosylmethionine (SAM) in baker's yeast ( Saccharomyces cerevisiae), ATP functions as both a precursor and a driving force. However, few published reports have dealt with the control of ATP concentration using genetic design. In this study we have adopted a new ATP regulation strategy in yeast for enhancing SAM biosynthesis, including altering NADH availability and regulating the oxygen supply. Different ATP regulation systems were designed based on the introduction of water-forming NADH oxidase, Vitreoscilla hemoglobin, and phosphite dehydrogenase in combination with overexpression of the gene SAM2. Via application of this strategy, after 28 h cultivation, the SAM titer in the yeast strain ABYSM-2 reached a maximum level close to 55 mg/L, an increase of 67% compared to the control strain. The results show that the ATP regulation strategy is a valuable tool for SAM production and might further enhance the synthesis of other ATP-driven metabolites in yeast.