Analysis and enhancement of the ethanol resistance of Pichia kudriavzevii N77-4, a strain newly isolated from the Korean traditional fermentation starter Nuruk, for improved fermentation performance

Author:

Sugiyama M,Fukaya T,Moon J Y,Ishida K,Matsushita A,Kim S Y,Yeo S H

Abstract

Abstract Nuruk is a traditional fermentation starter used for making starch-based Korean alcoholic drinks. The yeast strain Pichia kudriavzevii N77-4 was newly isolated from nuruk. Resistance to ethanol stress is a crucial characteristic in alcoholic beverage production, but the ethanol stress-resistance of P. kudriavzevii remains to be clarified. In this study, we attempted to analyze the ethanol resistance of P. kudriavzevii N77-4, and to improve it by ethyl methanesulfonate (EMS) mutagenesis. After 4 h of cultivation in 5% ethanol, N77-4 showed a growth defect accompanied with accumulation of reactive oxygen species (ROS). In addition, exposure of N77-4 to ethanol stress induced a more than 3-fold increase in the expression of PkSOD2, which encodes a superoxide dismutase, indicating that the strain was able to generate PkSOD2 to decrease ROS. EMS mutagenesis was performed to improve the ethanol resistance of N77-4. An isolated mutant, HER8, exhibited higher ethanol resistance, a 50% decrease in ROS accumulation, and enhanced expressions of PkGPX2, which encodes a glutathione peroxidase, and PkSOD1. Moreover, HER8 showed 10% greater ethanol production, indicating that up-regulation of these antioxidant genes is important for improving ethanol resistance in P. kudriavzevii, and use of the HER8 strain will improve the brewing fermentation.

Publisher

IOP Publishing

Subject

General Physics and Astronomy

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