Enzymatic pretreatment of algal biomass for enhanced conversion to biogas

Abstract

"This paper presents a method for the enzymatic pretreatment of algal biomass used as a fermentation substrate in anaerobic bioreactors for biogas production, in order to improve the energy efficiency of the biogas systems. The pretreatment method aims at breaking compact carbohydrates (cellulose and hemicelluloses) macromolecular structures from algal biomass under the action of a hydrolytic enzymes mixture secreted by the fungal species Trichoderma reesei, Trichoderma versicolor, Penicillinum chrysosporium, Fusarium solani, Chaetomium thermophile and Myrothecium verrucaria, thus facilitating access of anaerobic fermentation bacteria to heavily biodegradable cellulosic fibres, reducing fermentation time length and implicitly increasing the biomethane yield of anaerobic reactors. The laboratory experiments involving the marine macroalgae Ulva sp. have proven a significant increase in the concentration and total volume of biomethane in the fermentation gas produced by the enzymatically pretreated sample with the selective fungal mixture, compared to the untreated sample. It is expected that such a non-corrosive pretreatment method can bring higher biomethane production with minimal conditioning costs and fewer process residues, thus increasing the biogas systems profitability."