Jun Shima

Lipid production through simultaneous utilization of glucose, xylose, and l-arabinose by Pseudozyma hubeiensis: a comparative screening study

Co-fermentation of glucose, xylose and l-arabinose from lignocellulosic biomass by an oleaginous yeast is anticipated as a method for biodiesel production. However, most yeasts ferment glucose first before consuming pentoses, due to glucose repression. This preferential utilization results in delayed fermentation time and lower productivity. Therefore, co-fermentation of lignocellulosic sugars could achieve cost-effective conversion of lignocellulosic biomass to microbial lipid. Comprehensive screening of oleaginous yeasts capable of simultaneously utilizing glucose, xylose, and l-arabinose was performed by measuring the concentration of sugars remaining in the medium and of lipids accumulated in the cells. We found that of 1189 strains tested, 12 had the ability to co-ferment the sugars. The basidiomycete yeast Pseudozyma hubeiensis IPM1-10, which had the highest sugars consumption rate of 94.1xa0%, was selected by culturing in a batch culture with the mixed-sugar medium. The strain showed (1) simultaneous utilization of all three sugars, and (2) high lipid-accumulating ability. This study suggests that P. hubeiensis IPM1-10 is a promising candidate for second-generation biodiesel production from hydrolysate of lignocellulosic biomass.

Stress Tolerance of Baker’s Yeast During Bread-Making Processes

During the fermentation of dough and the production of baker’s yeast, cells of baker’s yeast are exposed to numerous and multiple environmental stresses including freeze–thaw, high-sucrose, and air-drying, the so-called baking-associated stresses. In addition, such stress conditions could induce oxidative stress in yeast cells with an increase in reactive oxygen species level because of the denaturation of proteins including antioxidant enzymes and the severe damage to the mitochondrial membrane or respiratory chain. To avoid lethal damage, baker’s yeast cells need to acquire a variety of stress-tolerant mechanisms, such as the induction of stress proteins, accumulation of stress protectants or compatible solutes, change of membrane composition, and repression of translation, by regulating the corresponding gene expression via stress-triggered signal transduction pathways. For example, proline and trehalose are important compounds involved in the stress tolerance of baker’s yeast. In fact, the engineering of proline and trehalose metabolism is a promising approach for the development of stress-tolerant baker’s yeast. Moreover, the multiomics approach such as comprehensive phenomics and functional genomics is promising for the identification of novel genes required for the stress tolerance. To further improve the fermentation ability or the production efficiency of yeasts, however, the detailed mechanisms underlying the stress response, adaptation, and tolerance of yeast cells should be understood. We believe that not only baker’s yeast, but also other important industrial yeasts with higher tolerance to various stresses, could contribute to the yeast-based industry for the effective production of bread doughs and alcoholic beverages or a breakthrough in bioethanol production.

Metabolic engineering of oleaginous fungus Mortierella alpina for high production of oleic and linoleic acids

The aim of this work was to study the molecular breeding of oleaginous filamentous Mortierella alpina for high production of linoleic (LA) or oleic acid (OA). Heterologous expression of the Δ12-desaturase (DS) gene derived from Coprinopsis cinerea in the Δ6DS activity-defective mutant of M. alpina increased the LA production rate as to total fatty acid to 5 times that in the wild strain. By suppressing the endogenous Δ6I gene expression by RNAi in the Δ12DS activity-defective mutant of M. alpina, the OA accumulation rate as to total fatty acid reached 68.0%. The production of LA and OA in these transformants reached 1.44 and 2.76g/L, respectively, on the 5th day. The Δ6I transcriptional levels of the RNAi-treated strains were suppressed to 1/10th that in the parent strain. The amount of Δ6II RNA in the Δ6I RNAi-treated strain increased to 8 times that in the wild strain.

Production of cis-11-eicosenoic acid by Mortierella fungi.

To find cis‐11‐eicosenoic acid (20:1ω9, EA)‐producing micro‐organisms.

Identification of a gene, FMP21, whose expression levels are involved in thermotolerance in Saccharomyces cerevisiae

Elucidation of the mechanism of high temperature tolerance in yeasts is important for the molecular breeding of high temperature-tolerant yeasts that can be used in bioethanol production. We identified genes whose expression is correlated with the degree of thermotolerance in Saccharomyces cerevisiae by DNA microarray analysis. Gene expression profiles of three S. cerevisiae strains showing different levels of thermotolerance were compared, and we chose three of them as candidate genes. Among these genes, FMP21 was investigated as a thermotolerance-related gene in S. cerevisiae by comparing the growth at high temperature with the gene expression in eight strains. The expression ratio of FMP21 at 37°C was correlated with the doubling time ratio at a coefficient of determination of 0.787. The potential involvement of the Fmp21 in the thermotolerance of yeasts was evaluated. The FMP21 deletion variant showed a decreased respiratory growth rate and increased thermosensitivity. Furthermore, the overexpression of FMP21 improved thermotolerance in yeasts. In conclusion, the function of Fmp21 is important for thermotolerance in yeasts.

Lactic Acid Bacteria Isolated from Japanese Fermented Fish (Funa-Sushi) Inhibit Mesangial Proliferative Glomerulonephritis by Alcohol Intake with Stress

The aim of this study was to examine the effect of heat-killed Lactobacillus paracasei NFRI 7415 on kidney and bone in mice fed an ethanol-containing diet with stress. Eight-week-old Crilu2009u2009:u2009u2009CD1 mice were fed a control diet (CD), an alcohol diet (AD) (35.8% of total energy from ethanol), or an alcohol diet containing 20% heat-killed Lb. paracasei NFRI 7415 (107u2009CFU/g) (LD) for 4 weeks. Mice in the AD and LD groups also underwent restraint stress for two weeks from 13 days. The mice were placed in a 50u2009mL plastic tube, which had a small hole drilled around its base to allow ventilation, and restrained for 1u2009h every day. High final body weight was in the following order: CD, LD, and AD (p < 0.05). The heat-killed Lb. paracasei NFRI 7415 lowered liver total cholesterol concentration and plasma glutamic-oxaloacetic transaminase (GOT) level. In addition, fecal bile acids of the LD group were higher than in the AD group (p < 0.05). The glomerulus of the kidney in the AD group was observed to be more fibrotic than in the CD and LD groups with azan stain. Immunostaining confirmed that brown areas indicating the existence of mesangial cells were increased in the AD group, but not in the CD and LD groups. These results indicated that the heat-killed Lb. paracasei NFRI 7415 inhibited mesangial proliferative glomerulonephritis by alcohol intake with stress.

Lactobacillus Paracasei NFRI 7415 Reduces Liver Lipid Contents in C57BL/6J Mice Fed a High-fat Diet

We examined the effects of Lactobacillus paracasei NFRI 7415 isolated from Japanese fermented fish (funa-sushi) on the whole-body and fat-tissue weights, plasma lipid concentration and hepatic lipid contents of mice. Male C57BL/6J mice were fed a control diet (CD), high-fat diet (HD) or HD containing Lb. paracasei NFRI 7415 (106 cfu/g) (HLD) for 10 weeks. The plasma triacylglycerol concentration of the HLD group was lower than that of the HD group. The plasma glucose, leptin and hepatic lipid concentration of the CD and LHD groups were lower than those of the HD group. As a result of measuring the liver lipids and the liver histology, it was observed that the number of lipid droplets in liver cells in the HD group was clearly greater than that in the CD and HLD groups. The total liver lipids in the CD and HLD group were lower than that of the HD group. This suggests that intake of Lb. paracasei NFRI 7415 is effective in overcoming the effects of HD to prevent hepatic lipid accumulation.

Environmental Stresses to Which Yeast Cells Are Exposed During Bioethanol Production from Biomass

Bioethanol is one of the most important renewable fuels for the reduction of global warming effects and environmental damage caused by the worldwide utilization of fossil fuels. Yeasts such as Saccharomyces cerevisiae are frequently used for bioethanol production from mono- or disaccharides derived from biomass, including sugar cane, corn, and lignocellulosic materials. During bioethanol production, yeast cells are exposed to various environmental stresses including chemical, temperature, oxidative, and acid stresses. The development of yeast strains tolerant to such environmental stresses must improve the bioethanol production process. This chapter focuses on the environmental stresses to which yeast cells are exposed during bioethanol production. We also discuss the exploration and breeding of stress-tolerant yeast strains and their application to bioethanol production.

Draft Genome Sequences of the Xylose-Fermenting Yeast Scheffersomyces shehatae NBRC 1983 T and a Thermotolerant Isolate of S. shehatae ATY839 (JCM 18690)

ABSTRACT Draft genome sequences of the type strain (NBRC 1983) and a thermotolerant isolate (ATY839) of the xylose-fermenting yeast Scheffersomyces shehatae were determined. The genome sizes and presumed open reading frames were highly similar between strains NBRC 1983T and ATY839.