Protein extracted from symbiotic culture of Chlorella pyrenoidosa and Yarrowia lipolytica shows structure-related detoxifying effects against 2, 2’-azobis (2-methyl-propanimidamidine) dihydrochloride induced oxidative stress

Abstract

We characterized the co-culture system of Chlorella pyrenoidosa and Yarrowia lipolytica to identify co-culture products of high application value. We first optimized the co-culture parameters using different ratios of algae and Y. lipolytica, which highlighted the competitive relationship between the two organisms. Analysis of pH values indicated that a relatively alkaline symbiotic co-culture might result in undetectable amounts of Y. lipolytica. The ratio of C. pyrenoidosa and yeast did not influence the balance of dissolved oxygen, but showed an influence on the production of chlorophyll A and total protein, with the protein content significantly increasing after 5 days of co-culture. Two protein hydrolysates were extracted from a single culture of C. pyrenoidosa and from a co-culture with Y. lipolytica (3:1 ratio) after 5 days. Structure analysis indicated a high molecular weight and composition of antioxidative-associated amino acids in the co-culture protein, and the two spatial structures were quite diverse; the co-culture protein showed formation of side chain vibrations and unordered structures. Notably, Y. lipolytica could stimulate the formation of superoxide dismutase and the chlorophyll a-b binding protein. In contrast to the protein from C. pyrenoidosa single culture, the co-culture protein showed remarkable protective effects on erythrocytes under oxidative stress, which may be attributed to its specific structure. The activities of antioxidative-associated enzymes were significantly lower than those in the control group (without protein), and the contents of oxidation-related metabolic products, including total glutathione, increased, while the glutathione disulfide content decreased significantly. We hypothesize that this C. pyrenoidosa-specific protein structure obtained from co-culture with Y. lipolytica consists of more exposed hydrophobic residues on the surface of protein molecules, resulting in enhanced antioxidative activity. Therefore, the protein from the yeast-algal symbiotic co-culture has a larger variable structure and shows potent anti-hemolytic activity under oxidative stress.