Bioethanol: Feedstock Alternatives, Pretreatments, Lignin Chemistry, andthe Potential for Green Value-Added Lignin Co-Products

摘要

Major challenges still exist in the cost-competitive production of cellulosic ethanol. Lignocellulose deconstruction using physiochemical pretreatments continues to be the most efficient way to remove lignin and expose cellulose for enzyme-mediated sugar reduction. Recent interest in the development of “value-added” lignin co-products and the desire to reduce the use of hazardous materials has prompted a resurgence of interest in alternative lignocellulosic feedstock and research into environment-friendly biological pretreatments. This article provides an overview of bioethanol processes and economics, standard and alternative feedstocks, physiochemical and biological pretreatments, and lignin chemistry. The chemistry and mode of action of ligninolytic and cellulolytic enzymes naturally expressed by white-rot and brown-rot fungi are described. This comprehensive review offers a renewed perspective on alternative high-lignin content cellulosic feedstock - specifically, bamboo - and the potential for microbial-based pretreatments that release cellulose for enzymatic breakdown and the subsequent fermentation of reduced sugars, while leaving lignin structures intact for conversion to valuable co-products.