Biogas production from high-protein and rigid cell wall microalgal biomasses: Ultrasonication and FT-IR evaluation of pretreatment effects

Abstract

Microalgal biomass is a valuable feedstock for biogas production, but the high protein content and the rigid cell wall are the main causes of disturbances in the methane fermentation process.In the paper, the influence of ultrasonic pretreatment of biomass of Chlorella vulgaris and Parachlorella kessleri, i.e. high-protein and rigid cell wall microalgal species, on their suitability for biogas production, was investigated. The ultrasonication effect was evaluated for the first time using Fourier transform infrared spectroscopy (FT-IR) of biomasses, and the fraction of neutral detergent fibre (NDF) isolated from the biomasses was analyzed. The results showed that the ultrasonic pretreatment of carbohydrate-rich biomass of P. kessleri caused a significant decrease in the content of structural complex carbohydrates and positive changes in the course of the methane fermentation process. On the contrary, the pretreatment of high-protein biomass of C. vulgaris negatively influenced its methane fermentation due to the aggregation of proteins and formation of a free NH2 group.