Enhanced fermentative performance under stresses of multiple lignocellulose-derived inhibitors by overexpression of a typical 2-Cys peroxiredoxin from Kluyveromyces marxianus

Jiaoqi Gao,Fengwu Bai,Hualiang Feng,Shengbo Hou,Shijun Zhong,Wenjie Yuan,Yimin Li

doi:10.1186/s13068-017-0766-4

Abstract

BackgroundBioethanol from lignocellulosic materials is of great significance to the production of renewable fuels due to its wide sources. However, multiple inhibitors generated from pretreatments represent great challenges for its industrial-scale fermentation. Despite the complex toxicity mechanisms, lignocellulose-derived inhibitors have been reported to be related to the levels of intracellular reactive oxygen species (ROS), which makes oxidoreductase a potential target for the enhancement of the tolerance of yeasts to these inhibitors.ResultsA typical 2-Cys peroxiredoxin from Kluyveromyces marxianus Y179 (KmTPX1) was identified, and its overexpression was achieved in Saccharomyces cerevisiae 280. Strain TPX1 with overexpressed KmTPX1 gene showed an enhanced tolerance to oxidative stresses. Serial dilution assay indicated that KmTPX1 gene contributed to a better cellular growth behavior, when the cells were exposed to multiple lignocellulose-derived inhibitors, such as formic acid, acetic acid, furfural, ethanol, and salt. In particular, KmTPX1 expression also possessed enhanced tolerance to a mixture of formic acid, acetic acid, and furfural (FAF) with a shorter lag period. The maximum glucose consumption rate and ethanol generation rate in KmTPX1-expressing strain were significantly improved, compared with the control. The mechanism of improved tolerance to FAF depends on the lower level of intracellular ROS for cell survival under stress.ConclusionA new functional gene KmTPX1 from K. marxianus is firstly associated with the enhanced tolerance to multiple lignocellulose-derived inhibitors in S. cerevisiae. We provided a possible detoxification mechanism of the KmTPX1 for further theoretical research; meanwhile, we provided a powerful potential for application of the KmTPX1 overexpressing strain in ethanol production from lignocellulosic materials.

Highlights

Bioethanol from lignocellulosic materials is of great significance to the production of renewable fuels due to its wide sources
Identification of a hypothetical typical 2‐Cys peroxiredoxin from K. marxianus Sequence analysis of KmTPX1 gene from K. marxianus Y179 was conducted in this study
The other four Prxs from S. cerevisiae have the lowest homologies with KmTPX1, which makes us even more certain that KmTPX1 should be identified as a hypothetical typical 2-Cys Prx (Fig. 1b)

Summary

Introduction

Bioethanol from lignocellulosic materials is of great significance to the production of renewable fuels due to its wide sources. Despite the complex toxicity mechanisms, lignocellulose-derived inhibitors have been reported to be related to the levels of intracellular reactive oxygen species (ROS), which makes oxidoreductase a potential target for the enhancement of the tolerance of yeasts to these inhibitors. Fuel ethanol has been the earliest and most mature biofuel product so far and widely considered as one of the most promising biomass energies. Bioethanol from lignocellulosic materials represents the most promising renewable fuel due to its wide range of sources. Toxic mechanisms of inhibitors in lignocellulosic hydrolysates are supposed to be extremely complicated. Exploring the toxicity of distinctive inhibitors to cells and its mechanism, and developing excellent strains with enhanced tolerance are becoming a more critical component of ethanol production from lignocellulosic materials. Mechanisms of toxicities of these inhibitors in yeasts are very complex and greatly variable depending on strains [3]

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Conclusion