**Author details**

*Biomass for Bioenergy - Recent Trends and Future Challenges*

were achieved for rice husk [98].

**5. Biological pretreatment**

high efficiency for delignification [41, 99].

for dilute acid treatment and 66.6% through alkali pretreatment. When sodium sulfite, sodium hydroxide, and sodium sulfide were used in SPORL pretreatment of switch grass, an improved digestibility of switch grass was achieved. When SPORL treatment was applied with optimized conditions, 97% lignin and 93% hemicellulose were removed from water hyacinth, and 90% hemicellulose and 75% lignin

Conventional methods for chemical and physical pretreatments require expensive reagents, equipment, and high energy. On the other hand, biological pretreatment requires live microorganisms for the treatment of lignocellulosic material, and this method is more environment friendly and consumes less energy. There are certain microorganism present in nature that exhibit cellulolytic and hemicellulolytic abilities. White-rot, soft-rot, and brown fungi are known for lignin and hemicellulose removal with a very little effect on cellulose. White rot is able to degrade lignin due to the presence of lignin degrading enzymes like peroxidases and laccases. Carbon and nitrogen sources are involved in the regulation of these degrading enzymes [41]. Cellulose is commonly attacked by brown rot, whereas white and soft rot target both lignin and cellulose contents of plant biomass. Commonly used white-rot fungi species are *Pleurotus ostreatus, Ceriporiopsis subvermispora, Ceriporia lacerata, Pycnoporus cinnabarinus, Cyathus cinnabarinus*, and *Phanerochaete chrysosporium. Basidiomycetes* species including *Bjerkandera adusta, Ganoderma resinaceum, Trametes versicolor, Fomes fomentarius, Irpex lacteus, Lepista nuda*, and *Phanerochaete chrysosporium* are also tested, and these species showed

Pretreatment of wheat straw was studied by Hatakka [100]. The results showed

13% conversion of wheat straw into sugars by *Pleurotus ostreatus* in duration of 5 weeks, whereas *Phanerochaete sordida* and *Pycnoporus cinnabarinus* showed almost the same conversion rate but in less time. For degradation of lignin in woodchips and to prevent cellulose loss, cellulase-less mutant of fungus *Sporotrichum pulverulentum* was developed [101]. Delignification of Bermuda grass by white-rot fungi *Ceriporiopsis subvermispora* and *Cyathus stercoreus* was studied that resulted in 29–32 and 63–77% improvement in delignification [102]. During the secondary metabolism in fungus *P. chrysosporium*, two lignin degrading enzymes, lignin peroxidase and manganese-dependent peroxidase, are produced in response to carbon and nitrogen limitation. Extracellular filtrates of various white-rot fungi contain these

**30**

two enzymes.

Muhammad Nauman Aftab1 \*, Irfana Iqbal2 , Fatima Riaz1 , Ahmet Karadag3 and Meisam Tabatabaei4

1 Institute of Industrial Biotechnology, Government College University, Lahore, Pakistan

2 Department of Zoology, Lahore College for Women University, Lahore, Pakistan

3 Faculty of Science, Bartın University, Bartın, Turkey

4 Agricultural Biotechnology Research Institute of Iran (ABRII), AREEO, Karaj, Iran

\*Address all correspondence to: nauman535@yahoo.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
