Biotransformation of Lignocellulosic Biomass to Value-Added Bioproducts: Insights into Bio-Saccharification Strategies and Potential Concerns

Lignocellulose is considered to be the most abundant and sustainable material on earth. The concept of lignocellulosic biomass conversion into value-added chemicals or materials is gaining in importance worldwide as a means of replacing conventional petrochemical resources for environmental sustainability. The production of biofuels such as bioethanol from lignocellulosic biomass consists of three main processes: pretreatment, enzymatic saccharification, and fermentation. As lignocellulose exhibits a highly recalcitrant structure, effective pretreatments are required for its deconstruction, making carbohydrates accessible for microbes to produce valuable bioproducts. These carbohydrate polymers (cellulose and hemicellulose) are then transformed into free monomeric sugars by the process of saccharification. Saccharification, especially enzymatic hydrolysis, is the crucial step for achieving lignocellulose bioconversion. Several strategies have been developed for diminishing biomass recalcitrance, ultimately improving the efficiency of product conversion, and reducing overall process costs. Some of these approaches include consolidated bioprocessing, consolidated bio-saccharification (on site), as well as simultaneous saccharification and fermentation, and separate hydrolysis and fermentation (off site). This review provides a detailed overview of current approaches to on-site and off-site saccharification and highlights the key factors for obtaining bioproducts from lignocellulosic feedstock via economically feasible bioconversion processes. Moreover, the key factors for process optimization and the production of various industrially important bioproducts from lignocellulosic biomasses are also summarized.