Engineering Clostridium acetobutylicum to utilize cellulose by heterologous expression of a family 5 cellulase

Abstract

Innovative processes to transform plant biomass into renewable chemicals are needed to replace fossil fuels and limit climate change. Clostridium acetobutylicum is of industrial interest because it ferments sugars into acetone, butanol and ethanol (ABE). However, this organism is unable to depolymerize cellulose, limiting its use for the direct transformation of lignocellulose. In this study, the freely secreted family 5 cellulase cphy2058 from Clostridium phytofermentans was efficiently expressed in C. acetobutylicum to enhance cellulolysis. RT-qPCR confirmed the transcription of the cellulase gene, and galactomannan and carboxymethyl cellulose plate assays showed endoglucanase and mannanase activity of cphy2058. ABE titers by the recombinant, cellulase-expressing C. acetobutylicum reached 85.83 mM in cellobiose cultures, whereas ABE titers by wild-type were 44.52 mM. ABE titers by the cellulase-expressing strain were similarly elevated relative to wild-type in cellulose and galactomannan cultures. These results demonstrate a novel strategy to enhance complex substrate utilization by heterologous cellulase expression in C. acetobutylicum.

Keywords:

• Fermentation
• biofuels
• gene expression
• bioprocessing
• bioproducts

Disclosure statement

No potential conflict of interest was reported by the author(s).