Studies On The Solid-state Fermentation Of Pomelo Peel For The Production Of Naringinase From Aspergillus Aculeatus

Citrus fruit is the biggest production in the world,and China is the largest producer whose acreage is more than the United States and Brazil.However,our country faces with the phenomenon of excess production,in another word,supply exceeds demand at present.In addition to the table,too much citrus fruit needs to process to juice or other storable products.During the process,the production appears bitterness or astringency which is the biggest problem.Naringinase is the hydrolytic enzyme which is dedicated to taking off the bitter and improving juice.Besides,the enzyme can be used to the field of pharmaceutical and biological transformation.At present,reseachers focuse on screening of strain,optimization of fermentation,purification of protein and identification of structure.Among them,the optimization of fermentation is submerged fermentation mainly and the study of solid-state fermentation is seldom which has so many advantages(low cost,less waste,and small pollution).Therefore,this paper is to establish the high-yielding fermentation of naringinase as the starting point using the by-products pomelo peel as material to produce naringinase,the mainly conclusions are as follows.(1)Solid-state fermetation of pomelo peel could produce naringinase from Aspergillus aculeatus JMUdb058 and the enzyme could hydrolyzed naringin in the juice efficiently.Addition of nitrogen source could increase the activity of naringinase significantly.However,the sterilization of medium(121 °C,20 min)decreased the naringinase production seriously.During the fermetation,both of the naringinase and ?-L-rhamnosidase were synthesized in the logarithmic grown phase rapidly,and its kinetic model showed that the syntheses of those two enzymes were strictly associated with the growth.(2)During the solid-state fermetation,the production of naringinase was supressed by the catabolism of glucose.Adding soybean meal or strach to much,it may lead to the effect of glucose catabolism and reduce the yelid of naringinase.(3)To optimize the fermetation of medium sterilization by irradiation,the results were as follows,diammonium hydrogen phosphate 10%(w/w),yeast extract 1.5%(w/w),ratio of solid to water 1:1(w/v),5 g pomelo peel powder per 250 m L shake flask,temperature at30 °C.Under this condition,the activities of naringinase and ?-L-rhamnosidase were 8.19IU/gds and 9.92 IU/gds,increased by 75% and 93% than the original medium.(4)Medium treated by autoclaved sterilization may lead to high concentration of sugar and this may inhibit the growth of Aspergillus aculeatus and the synthesis of naringinase.Adding water to medium can reduce the high concentration of sugar and improve the properties of medium.The optimization processes of medium treated by autoclaved sterilization were as follows,5 g of pomelo peel,ratio of solid to water 1:1.5(w/v),diammonium hydrogen phosphate 30%(w/w),soybean meal 1.5%(w/w),cultivated for 6 days.Under this condition,the activities of naringinase and ?-L-rhamnosidase were 5.69 IU/gds and 11.10 IU/gds.This paper suggests that pomelo peel is a good material for naringinase fermetation,and it is an effective way to produce naringinase from Aspergillus aculeatus on soild-state fermetation.By setting up the fermetation of medium treated by irradiation sterilization and autoclaved sterilization,the production of naringinase was improved significantly.These results establish a fundation for further study of naringinase production and its application.