Furfural induces reactive oxygen species accumulation and cellular damage in Saccharomyces cerevisiae

Abstract

BackgroundBiofuels offer a viable alternative to petroleum-based fuel. However, current methods are not sufficient and the technology required in order to use lignocellulosic biomass as a fermentation substrate faces several challenges. One challenge is the need for a robust fermentative microorganism that can tolerate the inhibitors present during lignocellulosic fermentation. These inhibitors include the furan aldehyde, furfural, which is released as a byproduct of pentose dehydration during the weak acid pretreatment of lignocellulose. In order to survive in the presence of furfural, yeast cells need not only to reduce furfural to the less toxic furan methanol, but also to protect themselves and repair any damage caused by the furfural. Since furfural tolerance in yeast requires a functional pentose phosphate pathway (PPP), and the PPP is associated with reactive oxygen species (ROS) tolerance, we decided to investigate whether or not furfural induces ROS and its related cellular damage in yeast.ResultsWe demonstrated that furfural induces the accumulation of ROS in Saccharomyces cerevisiae. In addition, furfural was shown to cause cellular damage that is consistent with ROS accumulation in cells which includes damage to mitochondria and vacuole membranes, the actin cytoskeleton and nuclear chromatin. The furfural-induced damage is less severe when yeast are grown in a furfural concentration (25 mM) that allows for eventual growth after an extended lag compared to a concentration of furfural (50 mM) that prevents growth.ConclusionThese data suggest that when yeast cells encounter the inhibitor furfural, they not only need to reduce furfural into furan methanol but also to protect themselves from the cellular effects of furfural and repair any damage caused. The reduced cellular damage seen at 25 mM furfural compared to 50 mM furfural may be linked to the observation that at 25 mM furfural yeast were able to exit the furfural-induced lag phase and resume growth. Understanding the cellular effects of furfural will help direct future strain development to engineer strains capable of tolerating or remediating ROS and the effects of ROS.

Evaluation of different lignocellulosic biomass pretreatments by phenotypic microarray-based metabolic analysis of fermenting yeast

“…In addition to energy efficiency, the use of excessive pre-treatment reaction conditions results in the formation of compounds which act as inhibitors to downstream processes including enzymatic saccharification and fermentations (Palmqvist et al, 1998;Chheda et al, 2007;Allen et al, 2010). These compounds are often the result of thermal or chemical degradation of liberated sugars (to furan based inhibitors) or lignin (to phenolic/hydroxycinnamic acid based inhibitors).…”

Effect of Low-concentration Furfural on Sulfur Amino Acid Biosynthesis in <i>Saccharomyces cerevisiae</i>

“…High concentrations of furfural have inhibitory effects on yeast growth 5) and fermentation 6) , but the mechanism of inhibition is still under investigation. For example, the addition of furfural is shown to induce the generation of reactive oxygen species in Saccharomyces cerevisiae 7) . Comprehensive analyses of the inhibitory mechanisms of furfural, 5-HMF, and acetic acid on yeast growth and fermentation 8) 10) have shown that more genes are down-regulated than up-regulated in the presence of these compounds 8) .…”

Evaluation of Non-Saccharomyces Cerevisiae Strains Isolated from Sea Water Against Inhibitory Compounds for Ethanol Production

“…5-HMF, furfural, acetic acid, formic acid and levulinic acid to determine the tolerance level to the inhibitors tested. These inhibitor have been shown to have toxic effects on cells which causing damage by inhibiting enzymes produced by microorganisms (Cantarella et al, 2004;Allen et al, 2010) or by impeding enzymes responsible for fermentation which then affecting their membrane integrity (Mills et al, 2009;Queìmeìneur et al, 2012). However, the result showed that both A. pullulans LBF-3-0074 and S. etchellsii LBF-3-0034 strains were still optimally grown in the 5-HMF-added medium ( Figure 2A).…”