Acetic acid is a common inhibitor present in lignocellulosic hydrolysate. Development of acetic acid tolerant strains may improve the production of biofuels and bio-based chemicals using lignocellulosic biomass as raw materials. Current studies on stress tolerance of yeast Saccharomyces cerevisiae have mainly focused on transcription control, but the role of transfer RNA (tRNA) was rarely investigated. We found that some tRNA genes showed elevated transcription levels in a stress tolerant yeast strain. In this study, we further investigated the effects of overexpressing an arginine transfer RNA gene tR(ACG)D and a leucine transfer RNA gene tL(CAA)K on cell growth and ethanol production of S. cerevisiae BY4741 under acetic acid stress. The tL(CAA)K overexpression strain showed a better growth and a 29.41% higher ethanol productivity than that of the control strain. However, overexpression of tR(ACG)D showed negative influence on cell growth and ethanol production. Further studies revealed that the transcriptional levels of HAA1, MSN2, and MSN4, which encode transcription regulators related to stress tolerance, were up-regulated in tL(CAA)K overexpressed strain. This study provides an alternative strategy to develop robust yeast strains for cellulosic biorefinery, and also provides a basis for investigating how yeast stress tolerance is regulated by tRNA genes.
Keywords: Saccharomyces cerevisiae; acetic acid stress; ethanol fermentation; lignocellulosic biomass; tRNA.