Enzymatic pretreatment of microalgae using fungal broth from Trametes versicolor and commercial laccase for improved biogas production

Abstract

Coupling microalgae production to wastewater treatment can reduce the costs of microalgae production for non-food bioproducts and energy consumption for wastewater treatment. Furthermore, microalgae anaerobic digestion can be enhanced by applying pretreatment techniques. The aim of this study is to improve the biogas production from microalgal biomass grown in urban wastewater treatment systems by applying an enzymatic pretreatment with crude fungal broth and commercial laccase. To this end, the fungus Trametes versicolor was cultured, and the enzymatic activity of the culture broth analysed by measuring laccase concentration. The results showed that both the fungal broth and commercial laccase pretreatment (100UL−1) over an exposure time of 20min increased the methane yield in batch tests. Indeed, the fungal broth pretreatment increased the methane yield by 74%, while commercial laccase increased the methane yield by 20% as compared to non-pretreated microalgal biomass. In this manner, laccase addition enhanced microalgal biomass anaerobic biodegradability, and addition of T. versicolor broth further improved the results. This fact may be attributed to the presence of other molecules excreted by the fungus.