Technological Advancements in Enzyme Production for 2G Ethanol

Bioethanol is projected as one of the major important renewable fuels with a pivotal role in reducing greenhouse gas emissions in the short term, as countries worldwide are adopting ethanol blending in gasoline due to the low-carbon footprint of 2G ethanol (2GE). While 1G ethanol technologies are mature and running, 2G has the unique advantage of better carbon capture and release figures and does not have the food versus fuel conflict. With 1GE poised to be phased out, there is huge pressure to have mature and cost-efficient 2GE technologies. The major bottleneck and cost contributor to 2GE production is the enzyme catalysts used in lignocellulose hydrolysis. While there are a few efficient biomass hydrolyzing enzyme cocktails in the market, the costs involved in using them for 2GE production do not seem to justify the returns, and onsite production of the enzyme is proposed for cost efficiency. Technological advancements in the production of enzymes for lignocellulose digestion need to be understood to identify the gaps and possibilities of further improvements in their hydrolytic efficiencies and address the lacunae of current production technologies and the enzymes themselves. The enzymes hydrolyzing biomass and their modes of action are introduced first, and the current status of cellulolytic enzyme production is elaborated focusing on the fugal sources of enzyme, production technologies, parameters affecting production, downstream operations, and creation of enzyme blends, specifically highlighting the challenges and the possibilities of improvement.