Furfural tolerance and detoxification mechanism in Candida tropicalis. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Wang, Shizeng; Cheng, Gang; Joshua, Chijioke; He, Zijun; Sun, Xinxiao; Li, Ruimin; Liu, Lexuan; Yuan, Qipeng
• Is Part Of: Biotechnology for biofuels. Volume 9:Issue 1(2016)
• Page Start: 1
• Page End: 11
• Publication Date: 2016-12
• Subjects: Candida tropicalis -- Furfural tolerance -- Furfural detoxification -- Alcohol dehydrogenase 1; Biotechnology -- Periodicals; Biomass energy -- Periodicals; Energy-Generating Resources -- Periodicals; 662.88
• DOI: 10.1186/s13068-016-0668-x
• Languages: English
• ISSNs: 1754-6834

Abstract

Abstract Background Current biomass pretreatment by hydrothermal treatment (including acid hydrolysis, steam explosion, and high-temperature steaming) and ionic liquids generally generate inhibitors to the following fermentation process. Furfural is one of the typical inhibitors generated in hydrothermal treatment of biomass. Furfural could inhibit cell growth rate and decrease biofuel productivity of microbes.Candida tropicalis is a promising microbe for the production of biofuels and value-added chemicals using hemicellulose hydrolysate as carbon source. In this study, C. tropicalis showed a comparable ability of furfural tolerance during fermentation. We investigated the mechanism ofC. tropicalis 's robust tolerance to furfural and relevant metabolic responses to obtain more information for metabolic engineering of microbes for efficient lignocellulose fermentation. Results Candida tropicalis showed comparable intrinsic tolerance to furfural and a fast rate of furfural detoxification.C. tropicalis 's half maximal inhibitory concentration for furfural with xylose as the sole carbon source was 3.69 g/L, which was higher than that of most wild-type microbes reported in the literature to our knowledge. Even though furfural prolonged the lag phase ofC. tropicalis, the final biomass in the groups treated with 1 g/L furfural was slightly greater than that in the control groups. By real-time PCR analysis, we found that the expression ofADH1 inC. tropicalis (ctADH1 ) was induced by furfural and repressed by ethanol after furfural depletion. The expression ofctADH1 could be regulated by both furfural and ethanol. After the disruption of genectADH1, we found thatC. tropicalis 's furfural tolerance was weakened. To further confirm the function ofctADH1 and enhanceEscherichia coli 's furfural tolerance, ctADH1 was overexpressed inE. coli BL21 (DE3). The rate of furfural degradation inE. coli BL21 (DE3) with pET-ADH1 (high-copy plasmid) and pCS-ADH1 (medium-copy plasmid) was increased by 1.59-fold and 1.28-fold, respectively. Conclusions Candida tropicalis was a robust strain with intrinsic tolerance to inhibitor furfural. The mechanism of furfural detoxification and metabolic responses were identified by multiple analyses. Alcohol dehydrogenase 1 was confirmed to be responsible for furfural detoxification.C. tropicalis showed a complex regulation system during furfural detoxification to minimize adverse effects caused by furfural. Furthermore, the mechanism we uncovered in this work was successfully applied to enhanceE. coli 's furfural tolerance by heterologous expression ofctADH1 . The study provides deeper insights into strain modification for biofuel production by efficient lignocellulose fermentation.