Yeast autolysis affects the flavor and quality of beer. The regulation of yeast autolysis is a need for industrial beer production. Previous studies on brewer's yeast autolysis showed that the citric acid cycle-related genes had a great influence on yeast autolysis. To explore the contribution of isocitrate dehydrogenase genes in autolysis, the IDP1 and IDP2 genes were destroyed or overexpressed in typical lager yeast Pilsner. The destruction of IDP1 gene improved the anti-autolytic ability of yeast, and the anti-autolytic index after 96 h autolysis was 8.40, 1.5 times higher than that of the original strain. The destruction of IDP1 gene increased the supply of nicotinamide adenine dinucleotide phosphate (NADPH) and the NADPH/NADP⁺ ratio was 1.94. After fermentation, intracellular ATP level was 1.8 times higher than that of the original strain, while reactive oxygen species (ROS) was reduced by 10%. The destruction of IDP2 gene resulted in rapid autolysis and a decrease in the supply of NADPH. Anti-autolytic index after 96 h autolysis was 4.03 and the NADPH/NADP⁺ ratio was 0.89. After fermentation, intracellular ATP level was reduced by 8% compared with original strain, ROS was 1.3 times higher than that of the original strain. The results may help understand the regulation mechanism of citric acid cycle-related genes on yeast autolysis and provide a basis for the selection of excellent yeast with controllable anti-autolytic performance.
Humans ; Isocitrate Dehydrogenase/genetics* ; NADP ; Reactive Oxygen Species ; Autolysis ; Adenosine Triphosphate

Mitophagy is a process whereby cells selectively remove mitochondria through the mechanism of autophagy, which plays an important role in maintaining cellular homeostasis. In order to explore the effect of mitophagy genes on the antioxidant activities of Saccharomyces cerevisiae, mutants with deletion or overexpression of mitophagy genes ATG8, ATG11 and ATG32 were constructed respectively. The results indicated that overexpression of ATG8 and ATG11 genes significantly reduced the intracellular reactive oxygen species (ROS) content upon H₂O₂ stress for 6 h, which were 61.23% and 46.35% of the initial state, respectively. Notable, overexpression of ATG8 and ATG11 genes significantly increased the mitochondrial membrane potential (MMP) and ATP content, which were helpful to improve the antioxidant activities of the strains. On the other hand, deletion of ATG8, ATG11 and ATG32 caused mitochondrial damage and significantly decreased cell vitality, and caused the imbalance of intracellular ROS. The intracellular ROS content significantly increased to 174.27%, 128.68%, 200.92% of the initial state, respectively, upon H₂O₂ stress for 6 h. The results showed that ATG8, ATG11 and ATG32 might be potential targets for regulating the antioxidant properties of yeast, providing a new clue for further research.
Mitophagy/genetics* ; Saccharomyces cerevisiae/genetics* ; Antioxidants ; Hydrogen Peroxide/pharmacology* ; Reactive Oxygen Species

Lager yeast is the most popular yeast strain used for beer production in China. The flocculation of yeast plays an important role in cell separation at the end of fermentation. Therefore, appropriately enhancing the flocculation capability of the lager yeast without affecting its fermentation performance would be desirable for beer industry. Our previous study showed that the defect of gene RIM21 might contribute to the enhanced flocculation capability of a lager yeast G03. To further investigate the role of the RIM21 gene in flocculation of strain G03, this study constructed a RIM21-deleted mutant strain G03-RIM21Δ through homologous recombination. Deletion of RIM21 improved the flocculation capability of strain G03 during wort fermentation at 11 °C without changing its fermentation performance significantly. The expression of FLO5, Lg-FLO1 and some other genes involved in cell wall integrity pathway were up-regulated in strain G03-RIM21Δ. In addition, the disruption of RIM21 enhanced resistance of yeast cells to cell wall inhibitors. These results provide a basis for elucidating the flocculation mechanism of lager yeast under low-temperature fermentation conditions.
Beer ; Fermentation ; Flocculation ; Receptors, Cell Surface ; Saccharomyces/metabolism* ; Saccharomyces cerevisiae/metabolism* ; Saccharomyces cerevisiae Proteins/metabolism*

1,3-1,4-β-glucanase (E.C.3.2.1.73) is an important industrial enzyme which cleave β-glucans into oligosaccharides through strictly cutting the β-1,4 glycosidic bonds in 3-O-substituted glucopyranose units. Microbial 1,3-1,4-β-glucanase belongs to retaining glycosyl hydrolases of family 16 with a jellyroll β-sandwich fold structure. The present paper reviews the industrial application and protein engineering of microbial β-glucanases in the last decades and forecasts the research prospects of microbial β-glucanases.
Amino Acid Sequence ; Glycoside Hydrolases ; Models, Molecular ; Protein Engineering ; Substrate Specificity

Yeast cell wall plays an important role in the establishment and maintenance of cell morphology upon the cell wall stress. The cell wall of yeast consists of β-glucans, mannoproteins and chitin. The composition and structure remodel due to cell wall stress. Brewer's yeast cell wall exhibits stress response during long-term acclimation in order to adapt to environmental changes. This paper reviews the composition and structure of yeast cell wall and the molecular mechanisms of cell wall remodeling and signal pathway regulation.
Cell Wall ; Chitin ; Saccharomyces cerevisiae

The autolysis of brewer's yeast seriously affects the quality of beer and the quality of yeast is considered as one of the key factors in beer brewing. Previous studies on brewer's yeast autolysis showed that RLM1 gene, an important transcription factor in cell integrity pathway, is closely related to the autolysis of yeast. In this study, RLM1 was knocked out and overexpressed in a haploid brewer's yeast. RLM1 disruption resulted in poor anti-autolysis performance of yeast, whereas overexpression of RLM1 contributed to the anti-autolytic ability of yeast. In addition, RLM1 gene knockout affected the osmotic stress resistance, cell wall damage resistance, nitrogen starvation resistance and temperature tolerance of yeast strain. The transcriptional level of GAS1 involved in cell wall assembly and DNA damage response was regulated along with the expression of RLM1, whereas other genes in CWI pathway did not show apparent regularity. RLM1 might mainly affect the expression of GAS1 so as to improve the stress resistance of lager yeast in harsh environment. The result from this study help further understand the mechanism of yeast autolysis and lay a foundation for breeding brewer's yeast strain with better anti-autolytic ability.
Autolysis ; Beer ; Cell Wall ; Humans ; MADS Domain Proteins ; Saccharomyces cerevisiae ; Saccharomyces cerevisiae Proteins

The morphological structure and physiological indexes of Saccharomyces cerevisiae have changed during serial re-pitching due to the stress conditions in serial handlings and the cells become aging. It is of great significance to study the physiological changes of S. cerevisiae during serial re-pitching to understand the anti-aging effect of S. cerevisiae. In this paper, the changes of the physiological indexes during re-pitching of yeast are summarized, and based on the analysis of the previous works further research directions are proposed.

Objective To analysis the risk factors,clinical manifestations of adnexal torsion(AT) during pregnancy,providing evidence for the early diagnosis of AT in pregnancy.Methods Retrospective data were collected from 40 women who underwent surgery for AT during pregnancy between May 2006 and August 2016 at the first affiliated hospital of Wenzhou Medical University.In addition,94 women diagnosed with non-torsion adnexal during pregnancy were chosen to serve as control subjects.The risk factors and clinical characteristics of the two groups wcre compared.Results AT during pregnancy were likely to occurring within the 6th and 14th week of gestation.The rate of the adnexal masses with sizes between 5 and 8cm was significantly higher in torsion group(P ＜ 0.05).The rate of ovarian hyperstimulation syndrome (OHSS) was shown to be obviously elevated in the torsion group (P ＜ 0.05).The white blood cell counts,neutrophil ratio,the rate of lacking of intra-adnexal blood flow on color Doppler imaging were significantly elevated in torsion group (P ＜0.05).Conclusion The risk factors of AT during pregnancy may be occured within the 6th and 14th week of gestation,cyst sizes between 5 and 8cm and combined with OHSS.Adnexal tumors bearing higher risks for torsion and should be strongly considered for an aggressive strategy of management during pregnancy.Moreover,the combined detection of the white blood cell counts and neutrophil ratio as well as doppler imaging can contribute to the early diagnosis of AT during pregnancy.

Brewer's yeast is crucial in beer fermentation, mainly beer flavor diversity and stability. Beer flavor stability is one of the most influential beer quality aspects, and screening or breeding brewer's yeast with enhanced anti-staling capacity will be an effective solution. In recent decades, with the progress of genetic engineering and detailed description of brewer's yeast genome, great efforts have been made to improve brewer's yeast. This review highlights recent advances in classical and genetic engineering improvement of yeasts to produce more antioxidant compounds or less beer aging substances and precursors. Therein, improvement targets, evaluation methods and development strategies of anti-staling brewer's yeast are also discussed. Furthermore, hotspot and future trend of anti-staling yeast strain development are also proposed.

Objective To examine the association between social isolation and cognitive function among the elderly living in the communities of Daqing city.Methods A total of 981 community residents aged 60 years or over,were surveyed with a questionnaire.Both Lubben Social Network Scale-6 (LSNS-6) and Montreal Congnitive Assessment (MoCA) Changsha Versions were used to respectively screen the status of social isolation and cognitive function,on these elderly.Results The average age was 71 years old for the 981 study participants.10.60％ (104/981) of the participants were assessed as having the status of social isolation,9.48％ (93/981) as having marginal family ties and 13.97％ (137/981) as having marginal friendship ties.Results from the multivariate linear regression analysis revealed that participants with higher scores of LSNS-6 presenting better cognitive function score,with a partial regression coefficient as 0.10 (P＜0.01).The MoCA scores in participants with social isolation (20.38 ± 5.54) were significantly lower than the ones without social isolation (22.10 ± 5.01) and the difference was statistically significant (P＜0.01).Social isolation was significantly related to the domain scores on visuo-spatial constructional executive functions (P=0.02),naming (P=0.03),language (P=0.01) and delayed memory functions (P＜0.01),but not with other domains as concentration (P=0.33),orientation (P=0.27) or abstraction (P=0.49).Conclusion The findings suggested that social isolation was mainly caused by the lack of friendship ties and associated with cognitive function and among the elderly in Daqing city,Heilongjiang province.