Pretreatment methods for converting straws into fermentable sugars

With the rapid progress in economics and society, the energy crisis and environmental issues have become more serious, and the development of more clean, efficient, renewable, and sustainable energy has thus attracted more attention. Straw resources are the most potential feedstocks, which are rich in organic content but are poorly utilized worldwide and exhibit great potential to produce biofuels and valuable chemicals. Straws belong to lignocellulosic biomass, which involves two major cascade biotransformation processes: (1) reducing sugars produced from lignocellulosic biomass by enzymatic hydrolysis, and (2) ethanol and other chemicals generated by further conversion of fermentable sugars. One of the most crucial factors is the pretreatment of lignocellulosic biomass, which is a prerequisite for effective production of fermentable sugars. In recent years, progress has been made in the development of more effectual pretreatment technologies and hydrolysis processes to increase sugar production. The focus of this chapter is to summarize the effects of different pretreatment methods for converting straws into fermentable sugar, including chemical, physical, physicochemical, biological, and combined treatment. Altogether, every pretreatment approach has its advantages and disadvantages, while combined technology can be effectively used for the process of saccharification for efficient conversion of straws into fermentable sugars.