Influence of a facile pretreatment process on lipid extraction from Nannochloropsis sp. through an enzymatic hydrolysis reaction

Abstract

Microalgal lipid is being considered as an alternative source of ω-3 polyunsaturated fatty acids (ω-3 PUFAs); however, the extraction of ω-3 PUFA-rich algal lipid still needs further research. In this study, single enzyme and their combinations were screened based on their cell wall disrupting capability and lipid recovery yield, and economical and feasible extraction parameters were determined. Lipid recovery could reach 22.18 ± 0.26 wt% when algae was treated with an 8 : 1 (w/w) algae/cocktail enzyme ratio and a 2 : 1 cellulase/lysozyme mass ratio at 50 °C under stirring for 5 h at a pH of 4.0, and the content of PUFAs was as high as 23.30%. In addition, alkaline pretreatment efficiently facilitates the degradation of algal cell wall in the enzymatic hydrolysis, and it has been verified that cell wall ruptures via two steps: swelling by a weak alkali pretreatment and decomposition by enzymatic hydrolysis. Furthermore, all the extraction operations can take place under facile conditions. These results imply that algal lipid extracted by a weak alkali pretreatment aiding enzymatic hydrolysis, is the most appropriate raw material for ω-3 PUFAs.