Effects of Enzyme-Microorganisms Synergy Treatment on Nutrient Functional Components and Biological Activities of Nannochloropsis oceanica

In order to improve the utilization value of N. oceanica, the effects of enzyme-bacteria synergy treatment on its nutritional and functional components as well as its biological activities were investigated. Papain was used to hydrolyze N. oceanica, and the enzymolysis process was optimized by single factor and response surface test. After fermented by lactic acid bacteria, the contents of total phenols, peptides and flavonoids as well as the antioxidant and hypolipidemic activities in vitro before and after fermentation were measured. Sensory evaluation was also performed. The results showed that the optimum enzymolysis process of N. oceanica was as follows: Enzyme amount 5.0%, pH8.0, enzymolysis time 4.0 h, enzymolysis temperature 76 ℃. Under this condition, the content of polypeptide significantly increased by nearly 1.3 times and the total phenolic content increased by 5.1%, while the total flavonoid content decreased by 32.5%. The antioxidant activity and pancreatic lipase inhibitory activity of the fermented products were enhanced, among which the DPPH free radical scavenging rate in mixed bacteria fermented group increased by 1.2 times, and the pancreatic lipase scavenging rate in mixed bacteria fermented group increased by 59.4%. Moreover, the sensory score of the sample after fermentation was significantly improved. In conclusion, the synergistic fermentation of enzyme-bacteria can significantly improve the polypeptide content, antioxidant activity, hypolipidemia activity and sensory properties of N. oceanica, thus provides reference and technical support for the development of functional fermentation products.