Research For Immobilized Aspergillus Niger K7 Producting Isomaltooligosaccharide

Aspergillus niger K7 is a strain screened with high a-glucoside enzyme activity in this group.In this paper,by studying to use immobilized Aspergillus niger K7 to convert cassava starch into product isomaltooligosaccharide(IMO),got sodium alginate as the immobilized cell carrier.By single factor experiment and response surface method optimization experiments to optimize immobilized cell carrier conditions,and by Box-Behnken experimental design(BBD)and response surface method to optimize and analyze immobilized cell carrier conditions,got the optimal conditions of immobilization carrier:sodium alginate 21g/L,calcium chloride 20g/L,the mycelium plus 87g/L,and particle diameter 3mm,immobilization time 120 min,under this condition,the enzyme activity of immobilized cells increased from initial 187.25U/g to 235.23U/g,nearly 25%.Under the optimal carrier conditions,researched the enzymatic properties of immobilized cell and known the optimal temperature 45 ℃,the optimal pH 5.5,the storage half-life 127d to immobilized cell.In the optimal immobilization conditions,optimized the reaction conditions of immobilized cell transforming cassava starch into IMO,and by single factor and orthogonal experimental design,got the best conversion condition:the speed 160r/min,the temperature 40℃,the initial pH 5.0,the colloidal dosage of immobilized cells 20ml,cassavastarch concentration 250 g/L.Under the optimal conversion conditions,which can be used for 20 batches continuously,the valid IMO content of remained stable and reached to 36.8%.Compared with the free mycelium,immobilized cells increased the stability of the intracellular enzyme significantly.On the basis of the shake flask experiments,had a research on the two different amplification process of conducting to product IMO in batches and flowing continuously to product IMO experiment for using immobilized cell technology to product IMO.In the simply enlarged experiments,to do pretreatment on the reaction system by pasteurization combined with temperature and initial pH value controlled,controlled effectively the phenomenon of bacterial contamination in the reaction process.Repeated the reaction for 10 batches in the 3.6L fermentor,the valid IMO content can reach more than 37.1%,the total IMO up to 67%.When the continuous reaction achieved to 36h in column reactor,the valid IMO content more than 40%,the total IMO up to 65%.