The hunt for alternative sources of energy generation that are inexpensive, ecofriendly, renewable and can replace fossil fuels is on, owing to the increasing demands of energy. One approach in this direction is the conversion of plant residues into biofuels wherein lignocellulose, which forms the structural framework of plants consisting of cellulose, hemicellulose and lignin, is first broken down and hydrolyzed into simple fermentable sugars, which upon fermentation form biofuels such as ethanol. A major bottleneck is to disarray lignin which is present as a protective covering and makes cellulose and hemicellulose recalcitrant to enzymatic hydrolysis. A number of biomass deconstruction or pretreatment processes (physical, chemical and biological) have been used to break the structural framework of plants and depolymerize lignin. This review surveys and discusses some major pretreatment processes pertaining to the pretreatment of plant biomass, which are used for the production of biofuels and other value added products. The emphasis is given on processes that provide maximum amount of sugars, which are subsequently used for the production of biofuels.

Keratinolytic potential of Pseudomonas aeruginosa strain SDS3 has been evaluated for the metabolism of chicken feathers. Results indicated that strain SDS3 showed complete metabolism of 0.1 and 0.5% (w/v) chicken feathers in minimal medium. Feathers were metabolized up to 80% at 1% (w/v) concentration. Maximum soluble protein (480.8±17.1 μg/mL) and keratinase (15.4±0.25 U/mL) were observed in the presence of 1% chicken feathers after five days of incubation. The effect of carbon and nitrogen sources showed that feather degradation was stimulated by complex carbon/nitrogen sources such as starch, malt extract, tryptone, and beef extract and was inhibited by simple carbon and nitrogen sources. Electricity production by employing chicken feathers as a substrate in microbial fuel cell (MFC) was evaluated. It was observed that maximum voltage corresponding to 141 mV was observed after 14 days of incubation. Maximum power density of 1206.78 mW/m² and maximum current density of 8.6 mA/m² were observed. The results clearly indicate that chicken feathers can be successfully employed as a cheap substrate for electricity production in MFC. This is the first report showing employment of chicken feathers as substrate in MFC.