Identification of Fusarium oxysporum Genes Associated with Lignocellulose Bioconversion Competency

Abstract

Fusarium oxysporum can convert straw to ethanol via consolidated bioprocessing (CBP)—a two-stage process that firstly involves aerobic saccharification and thereafter an oxygen-limiting fermentation phase. The efficacy of CBP is dependent upon the fungal strain used. Using suppression subtractive hybridisation (SSH), a total of 210 transcripts were identified as being overexpressed in a high as compared to low efficacy CBP strain in the aerobic and oxygen-limiting growth stages on a straw/bran mix. These transcripts encode proteins assigned to various categories, including carbohydrate metabolism, energy, protein and sugar transport and detoxification. Real-time RT-PCR analysis of 12 transcripts, including an endoglucanase III (EGIII), a novel ricin toxin A1 chain-like protein (RTA1), and two unknown transcripts (JX308289 and JX308290) validated the SSH findings. Post-transcriptional silencing of EGIII, RTA1 and an unknown transcript JX308289 in F. oxysporum strain 11C significantly reduced the capacity of the fungus to produce ethanol from a straw/bran mix. Thus these and other genes identified in this study are likely factors that determine the efficacy of CBP and such genes can be used as candidates for enhancing microbial ethanol production from straw and other lignocellulosic substrates.