Recent advances in process modifications of simultaneous saccharification and fermentation (SSF) of lignocellulosic biomass for bioethanol production

Abstract

The utilization of lignocellulosic biomass for second-generation (2G) bioethanol promotes green energy. Simultaneous saccharification and fermentation (SSF) is the first integrated bioprocess for both hydrolysis and fermentation. It's designed to primarily tackle enzyme inhibition during ethanol production. However, certain limitations have led to modifications in the traditional or batch SSF process to improve overall performance and yield. Recent SSF modifications have shown significant progress, with improvements in both enzyme technology and tailored strains for SSF. This has led to more efficient hydrolysis and fermentation. Experimental work plays a crucial role in providing insights into techno-economic and life-cycle assessments. Improvements in SSF involve key factors like biomass pretreatment, enzyme characteristics, hydrolysis duration, yeast strain selection, fermentation duration, co-fermentation strategies, and the integration of multiple stages. Notably, incorporating fed-batch modes and pre-saccharification into SSF allows handling high solids loading with improved ethanol concentrations. Design principles, including the structural characterization and evaluation of a bioprocess plant, are integral to the successful modification of SSF. Plant design for ethanol production is focused on the plant configuration, equipment size, and number of units with regards to reducing the total capital investment cost. Performing techno-economic analysis and life cycle assessment shows that SSF modifications reduce the use of enzymes and chemicals, resulting in cost savings and environmental benefits. The SSF modifications hold the promise of more sustainable and economically viable biofuel production, aligning with the global transition to greener energy sources.