Biohydrogen production from lignocellulosic hydrolysate: Unveiling the synergistic impact of substrate concentration and furfural inhibition.

Abstract

Lignocellulosic biomass offers substantial potential as an ideal feedstock for dark fermentative hydrogen production due to its sustainability and cost-effectiveness. The current study examined the influence of furfural on fermentative hydrogen production using lignocellulosic hydrolysate in the presence of furfural. Synthetic lignocellulosic hydrolysate, consisting primarily of 76% xylose, 10% glucose, 9% arabinose, and a mixture of other sugars such as galactose and mannose (85% pentose sugars and 15% hexose sugars), was employed as the substrate. Various substrate concentrations ranging from 2 to 32g/L were tested, along with furfural concentrations of 0, 1, and 2g/L. The investigation aimed to assess the effects of initial substrate concentration, initial furfural concentration, furfural-to-biomass ratio (F/B), and furfural-to-substrate ratio (F/S) on biohydrogen production yields. The maximum specific substrate utilization rates at different substrate concentrations were effectively characterized using Haldane's substrate inhibition model. Among the tested concentrations, the 16g/L emerged as the optimal substrate concentration. The initial furfural concentration was identified as the most significant parameter impacting biohydrogen production, with complete inhibition observed at a furfural concentration of 2g/L. Higher F/S ratios at substrate concentrations ranging from 2 to 16g/L resulted in reduced maximum specific hydrogen production rates (MSHPR) and hydrogen yields. Substrate inhibition was observed at 24g/L and 32g/L. Lactate was the predominant metabolite in all batches containing 2-g/L furfural, as well as in batches with 1-g/L furfural and substrate concentrations of 24 and 32g/L. Furfural at a concentration of 1g/L was not inhibitory in any of the batches. Overall, the mixed cultures in this study could efficiently produce hydrogen from lignocellulosic hydrolysates and degrade furfural, providing new insights into fermentative hydrogen-producing bacteria with furfural tolerance.