A Core-shell Structured Immobilized Lipase Production And Its Application In High Temperature Reaction

Lipase can catalyze hydrolysis,esterification,transesterification and a series of other reactions.Therefore,it is widely used in the fields of medicine,food,cosmetics and other industries,and has huge market value.Immobilized enzyme overcomes the disadvantages of free lipase,such as high cost,poor stability and difficulty in recovery and reuse.It is conductive to reduce the cost of production and produce continuously in industry.This paper aims to develop a preparation process of core-shell structured immobilized enzyme,which can improve temperature tolerance of lipase.In this study,diatomite,bamboo fiber and mycelium from Rhizopus arrizus were selected as carriers to immobilize Candida sp.99-125 lipase.The effects of carrier pretreatment conditions and the influencing factors(such as sodium alginate concentration,calcium chloride concentration and calcification time)in the process of adsorption-embedding on the performance of immobilized lipase were investigated,and the optimal conditions for the preparation of immobilized lipase were optimized.Then the structure of the immobilized lipase were characterized by scanning electron microscope,energy spectrometer and specific surface area meter.Finally,the immobilized lipase were applied to the synthesis system of wax esters to inveatigate the thermal stability and enzyme life.The preparation process of Candida sp.99-125 lipase with three different carriers was determined as follows:Firstly,Candida sp.99-125 lipase was immobilized with diatomite as the carrier.After optimization,immobilized lipase with core-shell structured was obtained.The preparation conditions of the immobilization process were 2 wt%sodium alginate,1 wt%calcium chloride and 120 min calcification time.At the same time,the immobilized lipase were used to catalyze the synthesis of wax esters.After repeated use of the lipase for 15 batches,the conversion rate of wax esters remained at 72%.The result indicated that the immobilized lipase had higher temperature tolerance and catalytic life.Then,Candida sp.99-125 lipase was immobilized with bamboo fiber as the carrier,and immobilized lipase with core-shell structured was obtained by optimizing experimental conditions.Optimum conditions of carrier pretreatment and immobilization preparation were as fellows:the carrier pretreated with 2 wt%sodium hydroxide,1.2 wt%sodium alginate,0.69 wt%calcium chloride and 100 min calcification time;After repeated use of the lipase for 20 batches,the conversion rate of wax esters remained at 81%.The result indicated that the immobilized lipase had higher temperature tolerance and catalytic life.Finally,Candida sp.99-125 lipase was immobilized with mycelium as the carrier,and the immobilized lipase had a core-shell structured.The optimal conditions obtained were 1 wt%sulfuric acid pretreatment carrier,1.1 wt%sodium alginate,0.76 wt%calcium chloride and 115 min calcification time.In the synthesis system of wax esters,the immobilized lipase were used for 20 batches,and the yield of wax esters remained 83%.The immobilized lipase produced by this process had good properties.Comparing the results of immobilized lipase with diatomite,bamboo fiber and mycelium,the immobilized lipase with mycelium pretreated by 1 wt%sulfuric acid was best.It had the highest stability.The immobilized lipase were used for 20 batches,and the conversion rate of wax esters remained 83%.