Study On Transformation Of Hesperidin Into Hesperitin-7-O-Glucoside By Fusarium Nivalve And Aspergillus Sojae

The output of oranges in China is relatively large,mainly for fresh food,and a small part is processed into canned and fruit juice.Orange peel is a by-product of orange processing,which will produce more than 10 million tons of orange peel every year.Among them,90% of orange peel is discarded,resulting in environmental pollution and waste of resources.Hesperidin is the main active ingredient in orange peel,which has great extraction and utilization value.However,its poor water solubility limits its application range.Molecular modification must be carried out to improve its solubility,so as to broaden its application range.Based on this,firstly,taking hesperidin as raw material,this paper screens the suitable strains by exploring the effect fermentation of hesperidin into hesperitin-7-O-glucoside fermented by Fusarium nivalve and Aspergillus sojae.Then,in order to further improve the health value of orange peel,using orange peel as raw material,the technological parameters of the transformation of hesperidin to hesperitin-7-O-glucoside by fermentation of orange peel with suitable strains are continuously improved,and the effect of inoculation sequence on the transformation efficiency is discussed.At the same time,the structure of the isolated hesperitin-7-O-glucoside is characterized.Hesperidin is used as raw material,and Fusarium nivale and Aspergillus sojae are used as the production strains for liquid submerged fermentation.High performance liquid chromatography and ultra-high performance liquid chromatography-mass spectrometry are used to analyze the fermentation products,α-L-rhamnosidase enzyme activity and pH of fermentation broth of the single strain(Fusarium nivale,Aspergillus sojae)and the mixed strains(Fusarium nivale : Aspergillus sojae =1:1)in different time periods.The effect of converting hesperidin to hesperitin-7-O-glucoside from single strain and mixed strains were emphatically compared at 30℃ and 160 r/min.The study showed that when P<0.05,there was significant difference between the mixed strains and the single strain in transforming hesperidin to hesperitin-7-O-glucoside;when fermentation lasted for 84 h,the enzyme activity of the mixed strains(104.81 U)was significantly higher than that of the single strain(24.73 U,26.17 U);Whether the mixed strains or the single strain,the transformation of hesperidin was completed under acidic conditions(pH 4.0～6.0).When the pH was 4.0～6.0,the maximum concentration of hesperitin-7-O-glucoside(63.52 μg/mL)was obtained by the mixed strains fermented for 84 h.Besides,the mixed strains became the suitable strain for orange peel fermentation.On this basis,orange peel was used as substrate and hesperitin-7-O-glucoside concentration was used as experimental index.The effect of hesperidin,the ratio of orange peel,the amount of liquid filling and the initial pH on the fermentation of orange peel by the mixed strains were explored,so as to determine the optimal scheme of orange peel fermentation.That is,30°C,160 r/min,hesperidin 0.04%,orange peel ratio of 4%,liquid filling volume of 50%,initial pH of 6.5,the fermentation time of 84 h,orange peel fermentation effect is the best.Based on the above scheme,the effect of different inoculation methods on the yield of hesperitin-7-O-glucoside were studied.The results showed that the inoculation sequence of Aspergillus sojae and then Fusarium nivale was more conducive to the transformation of hesperidin.In particular,on this premise,if the inoculation time of the two strains differed by 24 h,the concentration of hesperitin-7-O-glucoside produced after 84 h of fermentation could reach the highest(90.00 μg/mL).Concentrating the fermentation broth is convenient for rapid separation and purification and preparation of hesperitin-7-O-glucoside solid compound.In addition,the compound structure was detected by high performance liquid chromatography and ultra-high performance liquid chromatography-mass spectrometry,which proved the feasibility of realizing the value-added utilization of orange peel through the fermentation of the mixed strains,and provided another idea for further excavating the potential value of orange peel.