Co-production of ethanol-hydrogen by genetically engineered Escherichia coli in sustainable biorefineries for lignocellulosic ethanol production

Abstract

This work shows the impact of the hydrogen and ethanol co-production –via dark fermentation– using a genetically engineered Escherichia coli in the environmental and economic sustainability of a lignocellulose-based biorefinery. Wheat straw (WS) and corn stover (CS) were used as feedstock. These were treated with either a 1.5% dilute sulphuric acid pretreatment (DAP) or an autohydrolysis followed by a 0.25% dilute sulphuric acid pretreatment (AH-VDAP) to compare the effect of the lignocellulosic matrix and its pretreatment as strategies for obtaining rich hemicellulosic hydrolysates, which were used as substrate in the dark fermentation experiments. The engineered E. coli strain used here increased 30% the co-production of hydrogen and ethanol compared to other genetically modified strains. Further, their impact on the profitability was determined on biorefinery conceptual designs incorporating the pretreatment and dark fermentation stages experimental results. The dark fermentation stage contributed with 20% to 30% of the total ethanol production in the lignocellulose-based biorefinery designs proposed here. Techno economic and sustainability analyses established that the biorefinery design using WS as feedstock and employing AH-VDAP presented the lowest negative environmental impact with the lowest Total Production Cost (TPC). This design produced 187,846 L EtOH/day with a TPC of $1.37 USD/L EtOH. The results showed that co-production schemes could be an alternative for lignocellulosic ethanol biorefineries.