米曲霉发酵大米中抗氧化物质对酪氨酸酶的抑制作用

本实验采用两种不同米曲霉菌种(Aspergillus soji,A.orgzae)在35℃和湿度>90%的条件下对大米进行固态发酵6 d,比较发酵大米在发酵过程中活性物质的金属螯合、多酚氧化酶抑制、氧自由基吸收能力及总酚含量的变化。A.orgzae发酵的大米在金属螯合、多酚氧化酶抑制和氧自由基吸收能力上优于A.soji,两者在总酚含量上没有较大差别,且在发酵第4 d时大米的上述四项活性都趋于稳定,故选取A.orgzae发酵4 d的大米探讨其所含活性物质对酪氨酸酶的抑制作用。采用Lineweaver-Burk双倒数法探讨A.orgzae发酵大米中活性物质对蘑菇酪氨酸酶催化L-多巴氧化的抑制作用并推测其抑制机理。同时,虾血淋巴和虾黑变的抑制实验也证明了米曲霉发酵大米对酪氨酸酶的有效抑制作用。

Tyrosinase Inhibitory Activity of Antioxidants in Fermented Rice by Aspergillus

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.