Abstract
Chitosan is worthy to be explored and utilized since it has plenty of magical properties and being abundant reserved. Chitosan produced by fermentation possessed many characteristics such as high molecular weight, high degree of deacetylation and high purity. It was suitable to be applied in biomedical area. A detailed manufacturing process of chitosan using fermentation had been established from the results of literature and experiments. The Absidia coerulea CCRC 32931 was cultivated in shake-flask with soy bean protein medium at 25℃. It provided higher yield of chitosan and weight-averaged molecular weight. Then cultivation was carried out in a 20-L airlift bioreactor with wire-mesh draft plates which possessed low shear stress, high oxygen transfer rate and well liquid mixing. The yield of chitosan was 2.98 g/l . Afterwards, a rise in the yield of chitosan to 4.98 g/l was achieved by using fed-batch cultivation with feedback intermittent feeding strategy. Evaluating the performance of pilot-scale airlift bioreactor with wire-mesh draft plates had been done from the following performance index: gas hold-up, liquid mixing time and volumetric oxygen transfer coefficient (KLa). The experimental results showed that the airlift bioreactor still had the characteristics of high oxygen transfer rate and well mixing after scale up. Besides, airlift bioreactors had the advantages of simple structure and low shear stress. Those advantages had great benefit on scale up of chitosan production by fermentation. The concluded results demonstrated that the scale up of chitosan produced by fermentation in airlift bioreactors with wire-mesh draft plates was feasible and practicable.