Assessment of enzyme addition strategies on the enhancement of lipid yield from microalgae

Enzymatic hydrolysis is emerging as a promising unconventional pretreatment method for disrupting microalgae cells. However, the sustainability of biological enzyme needs to be improved due to low efficiency of enzymatic hydrolysis with single enzyme. Cellulase, xylanase, pectinase, snailase, lysozyme and trypsin were selected to pretreat microalgae Scenedesmus sp. for lipid extraction. The results shown that the pretreatment of a multi-enzyme combination of cellulase, xylanase and pectinase perform a better enzymatic hydrolysis effect than each single enzyme. Results shown that different sequences of enzymatic hydrolysis had a significant effect on the lipid extraction performance from microalgae, the lipid recovery yield of 100% (total lipids content) could be achieved with the sequence of stepwise enzymatic hydrolysis: pectinase (10 mg g-1 dry weight microalgae), cellulase (20 mg g-1) and xylanase (14 mg g-1). The SEM image, FTIR measurement, HPLC and XPS analysis indicated that the outer layer of trilaminar sheaths in the microaglal cell walls was first degraded by pectinase, and then cellulose and hemicellulose in the inner layer were destroyed by cellulase and xylanase. This study provides an efficient and environmental-friendly route for lipid extraction as a new strategy of enzymatic hydrolysis to valorize high-value added products in microalgae downstream processing.