Chamnipa Nuttaporn, Thanonkeo Sudarat, Klanrit Preekamol, Thanonkeo Pornthap
Khon Kaen University, Graduate School, Khon Kaen, Thailand; Khon Kaen University, Faculty of Technology, Department of Biotechnology, Khon Kaen, Thailand.
Mahasarakam University, Walai Rukhavej Botanical Research Institute, Maha Sarakam, Thailand.
Braz J Microbiol. 2018 Apr-Jun;49(2):378-391. doi: 10.1016/j.bjm.2017.09.002. Epub 2017 Nov 4.
High potential, thermotolerant, ethanol-producing yeasts were successfully isolated in this study. Based on molecular identification and phylogenetic analysis, the isolated thermotolerant yeasts were clustered in the genera of Pichia kudriavzevii, Candida tropicalis, Candida orthopsilosis, Candida glabrata and Kodamea ohmeri. A comparative study of ethanol production using 160g/L glucose as a substrate revealed several yeast strains that could produce high ethanol concentrations at high temperatures. When sugarcane bagasse (SCB) hydrolysate containing 85g/L glucose was used as a substrate, the yeast strain designated P. kudriavzevii RZ8-1 exhibited the highest ethanol concentrations of 35.51g/L and 33.84g/L at 37°C and 40°C, respectively. It also exhibited multi-stress tolerance, such as heat, ethanol and acetic acid tolerance. During ethanol fermentation at high temperature (42°C), genes encoding heat shock proteins (ssq1 and hsp90), alcohol dehydrogenases (adh1, adh2, adh3 and adh4) and glyceraldehyde-3-phosphate dehydrogenase (tdh2) were up-regulated, suggesting that these genes might play a crucial role in the thermotolerance ability of P. kudriavzevii RZ8-1 under heat stress. These findings suggest that the growth and ethanol fermentation activities of this organism under heat stress were restricted to the expression of genes involved not only in heat shock response but also in the ethanol production pathway.
本研究成功分离出了具有高潜力、耐热且能产乙醇的酵母。基于分子鉴定和系统发育分析，分离出的耐热酵母聚类于库德里阿兹威毕赤酵母属、热带假丝酵母属、近平滑假丝酵母属、光滑假丝酵母属和奥默柯达酵母属。一项以160g/L葡萄糖为底物的乙醇生产比较研究表明，有几种酵母菌株能在高温下产生高浓度乙醇。当以含有85g/L葡萄糖的甘蔗渣水解物为底物时，名为库德里阿兹威毕赤酵母RZ8-1的酵母菌株在37°C和40°C时分别表现出最高乙醇浓度，为35.51g/L和33.84g/L。它还表现出多重胁迫耐受性，如耐热、耐乙醇和耐乙酸。在高温（42°C）乙醇发酵过程中，编码热休克蛋白（ssq1和hsp90）、乙醇脱氢酶（adh1、adh2、adh3和adh4）和甘油醛-3-磷酸脱氢酶（tdh2）的基因上调，这表明这些基因可能在热胁迫下库德里阿兹威毕赤酵母RZ8-1的耐热能力中起关键作用。这些发现表明，该生物体在热胁迫下的生长和乙醇发酵活性不仅受参与热休克反应的基因表达限制，还受乙醇生产途径相关基因表达的限制。
