Pretreatment and fermentation of lignocellulosic biomass: reaction mechanisms and process engineering

In the time of rapidly depleting petroleum resources, worldwide food shortages, and solid waste problems, it is imperative to promote dedicated research into using an appropriate pretreatment technique utilizing regeneratable raw materials such as lignocellulosic biomass. However, not all pretreatment techniques are viable alternatives for industrial practice. Pretreatment is an important step to upgrade different kinds of lignocellulosic biomass into more valuable products, including biofuels and bio-based industrial chemicals. Most of the pretreatment techniques have their limitations or weaknesses, including high operational costs and temperature, toxicity and corrosiveness to the instrument, etc., while, some other pretreatment methods such as biological and plasma pretreatment are green procedures that can also be used to alter the physical and chemical properties of lignocellulosic materials. Although our present understanding is still low and not much research has been done to guarantee which pretreatment method is the reliable alternative, the combination of different pretreatment methods could be a good strategy to overcome the limitations of each approach. This review presents an overview of different pretreatment methods of lignocellulosic biomass to increase the rate and the degree of cellulose hydrolysis and subsequent processing steps as well as future perspectives.