Hydrogen and butanol production from native wheat straw by synthetic microbial consortia integrated by species of Enterococcus and Clostridium

Abstract

Abstract A consolidated two-stage bioprocessing scheme integrates the hydrogen and acetone–butanol–ethanol (ABE) production from wheat straw (WS). In the first stage, hydrogen production was performed from the xylan fraction of native WS with synthetic microbial consortia integrated by epiphytic species of Enterococcus. Three species showed a synergic effect between them attaining the maximum production of 79.5 mL H2 per gram of added wheat straw xylose. In the second stage, ABE production was carried out from biologically treated WS enriched in cellulose with a coculture of Clostridium beijerinckii 10132 with Clostridium cellulovorans 35296. The maximum ABE production was 23.3 g/L obtained in 5 days (3.7 g/L ethanol, 14.2 g/L butanol, and 5.4 g/L acetone). The structural changes in the WS were analyzed by FTIR and X-ray diffraction. The biological treatment applied to the native WS reduced the contents of lignin, hemicellulose and amorphous cellulose, increasing the cellulose availability for ABE production. This work proposes a biorefinery for hydrogen and ABE production from native wheat straw using two synthetic microbial consortia with hydrolytic and fermentative capacities. This configuration obviates the need for dedicated units for exhaustive pretreatments, enzyme production, and cellulose saccharification, which could reduce the operational costs considerably.