Studies On Production Of Curdlan By Immobilized Cells

Curdlan is a heat-gelable bacterial polysaccharide. It could be widely used as food additives or ingredients and has been found wide spread commercial uses. The immobilized cell technology is a new biological engineering technique. It offers a number of advantages over free-cell fermentations, including greater productivity, long-term operating stability, improved process control, and the ability to apply high dilution rates in continuous processes. In this dissertation, curdlan production by immobilization cells, involved the selected of the carrier, the optimal immobilization conditions, culture conditions and medium were studied also.L-15 cells were embedded in various carriers and utilized them for curdlan continuous fermentation. After multiply compared with each other in the mechanical strengths of the prepared gels, the yield of the curdlan and manufacturing procedures. The sodium alginate and PVA hydrogel are selected as better carrier for immobilized cells.Taking the curdlan yield and immobilized cell's mechanical strengths as experimental criteria, the optimal immobilization is determined by means of immobilizing L-15 on the sodium alginate and making cross-test. And two kinds of methods: one is to add to natural substances and the other is to do surface chemical treatment are studied to improve the character of the calcium alginate immobilized cells. Meanwhile, using PVA hydrogel, the optimal immobilization is researched. Furthermore, compare with the property of the two immobilized cells, the result reveals that PVA hydrogel is better than calcium alginate.By trial and error, final medium is resulted: saccharose 4%, NH4H2PO4 0.03%,KH2PO40.15%, MgSO47H2O0.1%, growth element 0.0025%, ZnCl2 0.0015%, FeSO4.7H2O 0.004%, reagent F 0.0015%, CaCO30.3%, pH was 7.5,the shaking speed was!70 r.p.m. Process temperature was kept as 32C.In these conditions, the curdlan production by PVA hydrogel immobilized cells is 3.3g/100ml.It more than the yield by free cells, the fermentation cycle was shorten to 72 hours, and it can be continuous fermentation. Curdlan production by this way has not been reported yet.