Abstract:Two Aspergillus strains (Aspergillus soji, A. orgzae) were used in this study for 6-day solid-state fermentation of rice at35°C and humidity >90%. The metal chelating, polyphenol oxidase inhibitory activity, oxygen radical absorbance capacity, and total phenolic contents of fermented rice during fermentation were analyzed. The rice fermented by A. orgzae had higher metal chelating, polyphenol oxidase (PPO) inhibitory activity and oxygen radical absorbance capacity (ORAC) than that fermented by A. soji. In terms of total phenol content, a similar fermentative effect was observed for both of the strains. In addition, these four properties of fermented rice tended to be stable at the fourth day of fermentation. Therefore, rice fermented by A. orgzae for four days was selected for the evaluation on anti-tyrosinase activity. Lineweaver-Burk Plot was adopted to investigate the inhibitory effects of bioactive compounds in fermented rice by A. orgzae on the oxidation of L-DOPA catalyzed by mushroom tyrosinase (M-PPO). The potential mechanism of the anti-tyrosinase activity was estimated based on the results of Lineweaver-Burk Plot. Moreover, the experiments on anti-melanosis of shrimp hemolymph and shrimp further supported the effective anti-tyrosinase activity of fermented rice by Aspergillus.
