One-pot pretreatment, saccharification and ethanol fermentation of lignocellulose based on acid–base mixture pretreatment

Abstract

Currently, for the production of cellulosic ethanol, multi-step unit operations, including pretreatment, solid/liquid (S/L) separation, solids washing, liquid detoxification, neutralization, enzymatic hydrolysis and fermentation, are the commonly required steps responsible for elevating the capital and operating costs. To simplify these steps, consolidated bioprocessing (CBP), focusing on the multi-functional microbial strains, was proposed. However, this process has not been commercialized yet. In this study, using an acid–base mixture as a pretreatment catalyst, pretreatment, saccharification and fermentation were performed in one pot without S/L separation, neutralization and detoxification. From the one-pot process based on the acid–base mixture pretreatment (190 °C, 2 min and 0.15 (w/v) acid–base mixture) and 15 FPU of cellulase per g glucan and Sacchromyces cerevisiae, 70.7% of the theoretical maximum ethanol yield (based on the initial amount of glucan in the untreated rice straw) was obtained. This was comparable to the estimated ethanol yield of 72.9%, assuming a 90% glucan recovery yield after pretreatment × a 90% glucose yield from saccharification × a 90% ethanol yield from ethanol fermentation performed in three separate pots. These results suggest that the entire slurry processing of lignocellulose in one pot could be an attractive way to achieve economic sustainability in the production of fuel from lignocellulose.