Rapid analysis and optimization of naringin enzymolysis by means of DNS method

[Objective] 3,5-Dinitrosalicylic acid(DNS) assay,a rapid detection method of naringin conversion rate established and used to analyze the dynamic process of naringin conversion into naringenin catalyzed by naringinase.[Methods] Naringinase was obtained from Aspergillus aculeatus JMUdb058 under solid-state fermentation.The 3,5-dinitrosalicylic acid(DNS) method was used to determine the yields of reducing sugars to calculate the conversion rate of naringin via a certain way.Then the conditions of naringin enzymolysis were optimized by traditional one-variable-at-a-time strategy.[Results] Good linear relationships were showed among the yields of reducing sugars and hydrolysis of naringin as well as the yields of naringenin in the process of naringin enzymolysis.Therefore,the DNS method that was used to determine the yields of reducing sugars can be applied to analyze the process of naringin bioconversion into naringenin by naringinase.The optimum operating conditions obtained from the one-variable-at-a-time design were temperature of 50 °C,pH value of 5.0,enzyme dosage of 8 U/mL,and substrate concentration of 0.2 g/100 mL.Under the optimal condition,the conversion rate of naringin reached 85% after 150 min.Then Km =413.44 mg/L and Vmax =0.022 g/(min·L) were got by the double reciprocal plot of Lineweaver-Burk.[Conclusion] The DNS assay can be used to analyze the process of naringin bioconversion into naringenin by naringinase,which provided a new convenient and simple method for study on naringin enzymolysis into naringenin.