Brazilian Journal of Microbiology Brazilian Journal of Microbiology
Braz J Microbiol 2018;49:378-91 - Vol. 49 Num.2 DOI: 10.1016/j.bjm.2017.09.002
Biotechnology and Industrial Microbiology
The potential of the newly isolated thermotolerant yeast Pichia kudriavzevii RZ8-1 for high-temperature ethanol production
Nuttaporn Chamnipaa,b, Sudarat Thanonkeoc, Preekamol Klanritb,d, Pornthap Thanonkeob,d,,
a Khon Kaen University, Graduate School, Khon Kaen, Thailand
b Khon Kaen University, Faculty of Technology, Department of Biotechnology, Khon Kaen, Thailand
c Mahasarakam University, Walai Rukhavej Botanical Research Institute, Maha Sarakam, Thailand
d Khon Kaen University, Fermentation Research Center for Value Added Agricultural Products, Khon Kaen, Thailand
Received 19 March 2017, Accepted 06 September 2017
Abstract

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.

Keywords
Pichia kudriavzevii, Thermotolerant yeast, Ethanol production, Gene expression, Sugarcane bagasse hydrolysate
Braz J Microbiol 2018;49:378-91 - Vol. 49 Num.2 DOI: 10.1016/j.bjm.2017.09.002
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