Biological pretreatments use microorganisms viz. fungi to solubilize the lignin. Biodelignification is the biological degradation of lignin by microorganism. Fungi have distinct degradation characteristics on lignocellulosic biomass. In general, brown and soft rots mainly attack cellulose while imparting minor modifications to lignin, and white-rot fungi more actively degrade the lignin component (Sun and Cheng 2002). Several white-rot fungi such as Phanerochaete chrysosporium, Ceriporia lacerata, Cyathus stercoreus, Ceriporiopsis subvermispora, Pycnoporus cinnabarinus, and Pleurotus ostreatus have been examined on different lignocellu — losic biomass showing high delignification efficiency (Kumar and Wyman 2009; Shi et al. 2008). Biological pretreatment by white-rot fungi has been combined with organosolv pretreatment in an ethanol production process by simultaneous sacchari­fication and fermentation (SSF) from beech wood chips (Itoh et al. 2003).

The biological pretreatment appears to be a promising technique and has very evident advantages, including no chemical requirement, low energy input, mild envi­ronmental conditions, and environmentally friendly working manner (Kurakake et al. 2007; Salvachua et al. 2011). However, its disadvantages are as apparent as its advantages since biological pretreatment is very slow and requires careful control of growth conditions and large amount of space to perform treatment. However, the main drawback to develop biological methods is the low hydrolysis rate obtained in most biological materials compared to other technologies (Sun and Cheng 2002).