Curtailing citrate buffer inhibition effect on S. cerevisiae to enhance the fermentability of cellulosic hydrolysate

Abstract The current investigation emphasizes the effect of different citrate buffer strengths on cellulose conversion efficiency during the enzymatic hydrolysis of pretreated sorghum stalks, and the subsequent fermentation of enzymatic hydrolysates to achieve the industrial titer of bioethanol. A set of enzymatic hydrolysis experiments were conducted in 50 mM, 5 mM and 0.5 mM citrate buffer mediums which contain dilute sulfuric acid pretreatment derived biomass as substrate. As a result, similar cellulose conversion efficiencies such as 68.7%, 68.8% and 69% were observed during enzymatic hydrolysis of pretreated biomass at 50 mM, 5 mM and 0.5 mM citrate buffer strengths, respectively. Enzymatic hydrolysates derived from 50 mM, 5 mM and 0.5 mM citrate buffer mediums has been fermented by S. cerevisiae, which resulted in ethanol yield of 0.38 gp/gs, 0.47 gp/gs, and 0.47 gp/gs, respectively. As per the fermentation results, it has been observed that, metabolic growth of S. cerevisiae has been hindered due to the presence of high concentration of citric acid (50 mM) in the enzymatic hydrolysate.