Simultaneous preparation of antioxidant peptides and lipids from microalgae by pretreatment with bacterial proteases

[Display omitted] •High antioxidant activity hydrolysates were obtained by enzymatic hydrolysis.•Radical scavenging activities were: DPPH 33.5%; OH• 46.8%; ORAC 7.4 µmol TE/µmol.•Enzymatic treatment reduces the amount of lipid leaching reagent by 35.34–45.49%.•Modified methods help to increase the amount and variety of extracted lipids.•Comprehensive utilization of algae can be achieved through enzymatic hydrolysis. Chlorella can produce large amounts of lipids and therefore has great potential for biodiesel production. In this study, Chlorella protothecoides was hydrolyzed by several kinds of extracellular bacterial proteases produced by Pseudoalteromonas sp. ZB23-2, B27-3 and JS4-1 before lipid extraction. Hydrolysates with high antioxidant activity were obtained. The scavenging activities of 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydrogen peroxide, and hydroxyl free radicals reached 33.47 ± 0.68%, 46.81 ± 2.38%, and 7.35 ± 0.37 µmol·TE/µmol, respectively. Likewise, proteolysis reduced biomass, which resulted in a reduction in lipid leaching reagents by 35.34–45.49%. Compared to the commonly used Kates and Paradis method (171.77 ± 2.50 mg/g), the modified ethanol lipid extraction combined with JS4-1 enzyme pretreatment (291.06 ± 1.70 mg/g) and acetone-ethanol lipid extraction combined with B27-3 protease pretreatment (277.20 ± 3.30 mg/g) resulted in a larger and more diverse lipid extraction. Protease pretreatment combined with less toxic solvents for lipid extraction improved microalgal biorefinery and reduced environmental pollution.