Enzymatic treatment of lignocellulosic wastes for anaerobic digestion and bioenergy production

Active research has been conducted on the production of biofuels from the abundant and inexpensive lignocellulosic wastes of forestry, agriculture, and municipal solid wastes. However, degradation of lignocellulose is hindered by the recalcitrant nature of lignocellulose. Hence, hydrolysis/saccharification of lignocellulose becomes the rate-limiting step for the fermentative production of cellulosic biofuels (such as H₂ and ethanol). Hydrolysis of cellulosic materials by biological means is environmentally benign and could be achieved either by using cellulolytic microorganisms or cellulolytic enzymes collected from those microorganisms. Biofuels production could be achieved by direct fermentation of raw lignocellulosic wastes or by a twostage process, in which the hydrolysis step and the anaerobic fermentation step are operated separately. In this chapter, we review the state-of-the-art of the following aspects related to the enzymatic hydrolysis of lignocellulosic wastes for anaerobic fermentation and bioenergy production: (1) structure of plant cell walls and their cellulose, hemicellulose, and lignin components; (2) lignocellulose-degrading microorganisms and their characterisitics; (3) production of enzymes degrading lignocellulose; (4) treatment of wastes using lignocellulose-degrading enzymes; and (5) anaerobic fermentation process for bioenergy production from enzymatically pretreated lignocellusic wastes.