Biological pretreatment offers some conceptually important advantages such as low chemical and energy use. However, a controllable and sufficiently rapid system has not yet been found. At the same time, chemical pretreatments have also serious disadvantages in terms of the requirement for specialized corrosion resistant equipment, extensive washing, and proper disposal of chemical wastes.

Table 9.14 Selected hydrolysis and fermentation strategies

Name Description Features

Biological pretreatment is a safe and environmentally friendly method for lignin removal from lignocellulose. Biological pretreatment comprises of using micro­organisms such as brown, white, and soft-rot fungi for selective degradation of lignin and hemicellulose out of which white-rot fungi seems to be the most effective microorganism. Lignin degradation occurs through the action of lignin­degrading enzymes such as peroxidases and laccase [136]. Biological pretreat­ments are safe, environmentally friendly, and less energy intensive compared to other pretreatment methods (Table 9.15). However, the rate of hydrolytic reaction is very low and needs a great improvement to be commercially applicable. Hat — akka [68] investigated the pretreatment of wheat straw using 19 white-rot fungi and found that 35% of the wheat straw was converted to reducing sugars after 5 weeks’ pretreatment with Pleurotus ostreatus compared to only 12% conversion of the untreated straw.