Elimination of carbon catabolite repression through gene-modifying a solventogenic Clostridium sp. strain WK to enhance butanol production from the galactose-rich red seaweed

With the determination of the Leloir pathway in a solventogenic wild-type strain WK through the transcriptional analysis, two pivotal genes (galK and galT) were systematically co-expressed to demonstrate a significantly enhanced galactose utilization for butanol production with the elimination of carbon catabolite repression (CCR). The gene-modified strain WK-Gal-4 could effectively co-utilize galactose and glucose by directly using an ultrasonication-assisted butyric acid-pretreated Gelidium amansii hydrolysate (BAU) as the substrate, exhibiting the optimal sugar consumption and butanol production from BAU of 20.31 g/L and 7.8 g/L with an increment by 62.35 % and 61.49 % over that by strain WK, respectively. This work for the first time develops a feasible approach to utilizing red algal biomass for butanol fermentation through exploring the metabolic regulation of carbohydrate catabolism, also offering a novel route to develop the future biorefinery using the cost-effective and sustainable marine feedstocks.

Automated summary

By determining the Leloir pathway in strain WK and co-expressing the genes galK and galT, carbon catabolite repression (CCR) was eliminated and galactose utilization for butanol production was significantly enhanced. The gene-modified strain WK-Gal-4 effectively co-utilized galactose and glucose using a pretreated red algal hydrolysate as the substrate, resulting in optimal sugar consumption and butanol production, with increments of 62.35% and 61.49% over strain WK, respectively. This work provides a feasible approach to utilizing red algal biomass for butanol fermentation and offers a novel route for the future development of cost-effective and sustainable marine biorefinery.