Fermentable sugar production from wet microalgae residual after biodiesel production assisted by radio frequency heating

Abstract In this study, the feasibility of comprehensive recovery of lipid and carbohydrate in wet microalgae Chlorella vulgaris was explored. First, four sets of enzyme combinations of α-Amylase, Amyloglucosidase and CTec2 were evaluated for hydrolysis efficiency on microalgae disrupted with radio frequency heating. Then, the most suitable combination was applied to raw microalgae and microalgae residual after biodiesel production, respectively, for saccharification. Adsorption kinetics of the optimized enzyme combination on the aforementioned three samples were determined and adsorption isotherm was analyzed by Freundlich equation. Morphology of microalgae was also investigated by scanning electron microscopy. A yield of reducing sugars in microalgae residual at 54.5% was obtained after 72 h saccharification. The results from enzyme adsorption kinetics, isotherm and SEM images were consistent with each other. This study demonstrated that the microalgae residual after biodiesel production could be used as carbohydrate feedstock for fermentable sugar production through simple enzymatic hydrolysis.