Fungal enzyme cocktail treatment of biomass for higher biogas production from leaf litter

Abstract

Biogas production from leaf litter (road sweepings of MSW) is difficult under normal conditions requiring longer retention time due to the complex chemistry involving interlinking structures of lignin and cellulose where in lignin is considered recalcitrant under anaerobic conditions while also limiting access to the cellulose and hemicelluloses. Pre-treatment of biomass with single enzymes system is expensive and uneconomic and an alternative option has been tried. P. florida “ready-to-fruit” bags were sprinkled with biogas digester liquid (BDL) from a plug-flow reactor (PFR) type biogas plant fed with leaf litter. Spraying BDL not only increased the mushroom yields from 1.6 to 2.3kg/kg substrate but also gave around ∼85ml of leachate rich in lignocellulolytic enzymes. Analysis of this enzyme cocktail at various stages of mushroom growth showed that on the 8d a combination of lignocellulolytic enzymes rich in peroxidase (46.67U/gTS) and laccase (204.38U/gTS) and low in cellulase (8.87U/gTS) could be obtained which can be used for various industrial applications such as softening of biomass for higher biogas production and/or bioethanol production. In this study the enzyme cocktail was used for softening paddy straw, a typical lingo-cellulosic biomass, for increasing biogas yields. This type of an enzyme treatment for paddy straw increased biogas yields by 29% and also enhanced sustainability by recycling end product of one process (mushroom cultivation) in softening biomass for higher biogas production and thereby overall system efficiency.