Bioactivity Evaluation of Crude Polysaccharide from Rice Bran Fermented by Preussia Aemulans and the Changes in its Nutritional Contents

Abstract

A new functional fungus named Preussia aemulans isolated from the Cordyceps sinensis fruiting body was fermented with rice bran (RB). Under the optimal conditions for polysaccharide fermentation (15% maltose, 3% yeast extract, 15 days of fermentation time and 60% moisture content) polysaccharide content was increased from 19.80 ± 1.23 to 71.16 ± 2.63 mg/g dry matter. The amino acid, protein, phenolics and nucleoside contents were also significantly improved. The crude polysaccharide (CPS) sample isolated from the fermented RB indicated significant antioxidant activity. The EC50 values of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid; ABTS.+) and hydroxyl radicals (HO•) scavenging activities were 0.74, 0.76 and 0.22 mg/mL, respectively. The FT-IR spectrum indicated CPS contained a β-glycosidic linkage. For immunomodulatory activities, CPS strongly stimulated proliferation of macrophages (170.03 ± 9.64%), and production of nitric oxide (15.01 ± 0.33 μM). Practical Applications An approach to reuse RB was developed in this research. RB is actually rich in vitamins, minerals, amino acids and essential fatty acids and could be used as a fermentation medium. Cordyceps sinensis is a rare resource due to its specific growth environment, and it is diminishing because of over-exploitation. The P. aemulans isolated from the C. sinensis fruiting body has similar physiological activity as C. sinensis. Using RB as a medium for fermentation by P. aemulans not only enables reuse of RB, but also ensures protection of a rare resource while enriching food diversity.