Abstract
Escherichia coli AH003, a derivative of E. coli KO11 with the L-lactate dehydrogenase (ldh) and pyruvate formate lyase (pfl) genes deleted and its parent strain E. coli KO11 were used as the ethanologen to convert glucose and gluconate to ethanol in M9 minimal medium. E. coli AH003 grew very poorly on glucose in M9 medium. However it achieved rapid growth when gluconate was used as the carbon source. The addition of gluconate to medium containing glucose improved the rate of glucose utilization. In contrast, E. coli KO11 grew well on both glucose and gluconate in M9 medium. The addition of gluconate to medium containing glucose did not improve the rate of glucose utilization. We believe that the deletion of the pfl gene in E. coli AH003 led to the different fermentation results. The co-fermentation of gluconate and glucose could be a useful strategy to improve the rate of glucose fermentation and decrease nutrient requirements for engineered strains lacking the pfl gene and grown under anaerobic conditions.
Highlights
Cellulosic biomass is an attractive, renewable, abundant, and lowcost feedstock for fuel and chemical production [1]
The cellulosic biomass hydrolysate mainly contains hexose and pentose sugars, which can be fermented to various fermentation products including ethanol
Our lab proposed an alternative route for biofuel and chemical production from cellulosic biomass in which cellobionate instead of monomeric sugars is produced as the reactive intermediate for subsequent fermentation [4]
Summary
Cellulosic biomass is an attractive, renewable, abundant, and lowcost feedstock for fuel and chemical production [1]. Their biochemical conversion features cellulase mediated hydrolysis and microbial fermentation. The cellulosic biomass hydrolysate mainly contains hexose and pentose sugars, which can be fermented to various fermentation products including ethanol. The addition of LPMOs to cellulase enzyme cocktails to enhance cellulose degradation generates cellobionic acid and gluconic acid in addition to pentose and hexose sugars in the hydrolysate [3]. Our lab proposed an alternative route for biofuel and chemical production from cellulosic biomass in which cellobionate instead of monomeric sugars is produced as the reactive intermediate for subsequent fermentation [4]. Conversion of gluconic acid or cellobionic acid to biofuels is of importance for complete utilization of all the carbon sources available in biomass
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