Effects of Chlorella vulgaris polysaccharides accumulation on growth characteristics of Trachemys scripta elegans

The present study investigated the effects of the accumulated polysaccharides in Chlorella vulgaris microalgae on the growth characteristics of Trachemys scripta elegans. Sodium alginate was used to prepare immobilized C. vulgaris, and the antioxidant effects of the accumulated polysaccharides in it were determined using Caenorhabditis elegans as a model. We determined the specific growth rates of T. s. elegans (10 in each group) and their levels of non-specific immune-related indexes (including alkaline phosphatase; total superoxide dismutase; catalase; malondialdehyde). Under optimal culturing conditions, the accumulated polysaccharide content in C. vulgaris reached 32.7% (dry weight). Polysaccharides from C. vulgaris significantly improved the hydrogen peroxide-induced oxidative stress resistance and resulted in the enhancement of stress resistance-related antioxidant enzymes, including total superoxide dismutase and catalase (p < 0.05). The accumulated polysaccharides in C. vulgaris were heteropolysaccharides comprising rhamnose, ribose, arabinose, xylose, 2-deoxy-D-glucose, mannose, glucose, galactose, and glucosamine with a molar ratio of 0.26: 0.62: 0.21: 0.10: 0.08: 0.18: 1.00: 0.42: 0.17. Compared with the control group with common feeds, suspended and immobilized C. vulgaris with higher accumulated polysaccharide levels had a positive effect on the specific growth rate of the T. s. elegans (p < 0.05). Further, the suspended and immobilized C. vulgaris with higher accumulated polysaccharide levels significantly increased serum alkaline phosphatase, total superoxide dismutase and catalase activity (p < 0.05) and decreased serum malondialdehyde levels of T. s. elegans (p < 0.05).