Abstract
BackgroundMultiple lignocellulose-derived inhibitors represent great challenges for bioethanol production from lignocellulosic materials. These inhibitors that are related to the levels of intracellular reactive oxidative species (ROS) make oxidoreductases a potential target for an enhanced tolerance in yeasts.ResultsIn this study, the thioredoxin and its reductase from Kluyveromyces marxianus Y179 was identified, which was subsequently achieved over-expression in Saccharomyces cerevisiae 280. In spite of the negative effects by expression of thioredoxin gene (KmTRX), the thioredoxin reductase (KmTrxR) helped to enhance tolerance to multiple lignocellulose-derived inhibitors, such as formic acid and acetic acid. In particular, compared with each gene expression, the double over-expression of KmTRX2 and KmTrxR achieved a better ethanol fermentative profiles under a mixture of formic acid, acetic acid, and furfural (FAF) with a shorter lag period. At last, the mechanism that improves the tolerance depended on a normal level of intracellular ROS for cell survival under stress.ConclusionsThe synergistic effect of KmTrxR and KmTRX2 provided the potential possibility for ethanol production from lignocellulosic materials, and give a general insight into the possible toxicity mechanisms for further theoretical research.
Highlights
Multiple lignocellulose-derived inhibitors represent great challenges for bioethanol production from lignocellulosic materials
Alignment of KmTrxR with other related TrxR sequences revealed that active site is highly conserved from bacteria to fungi
An enhanced tolerance of yeasts to multiple lignocellulose-derived inhibitors contributes to the process of lignocellulosic ethanol production
Summary
Multiple lignocellulose-derived inhibitors represent great challenges for bioethanol production from lignocellulosic materials. These inhibitors that are related to the levels of intracellular reactive oxidative species (ROS) make oxidoreductases a potential target for an enhanced tolerance in yeasts. Destroying the complex structure of lignocellulose mainly depends on some physicochemical methods like steam explosion, acids or alkali, which may generate inhibitors [3], such as weak. Mechanisms of toxicities of these inhibitors in yeasts are very complex and greatly variable depending on strains [9]. Inhibitors like acetic acid, furfural and phenol have been reported to be related to the redox state inside cells, inducing reactive oxidative species (ROS) generation [10,11,12]
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