| Pullulan is a major polysaccharide produced by strains of Aureobasidium pullulans. It can be produced by fermenting with sugar such as hydrolyzed amylum,sucrose and glucose. The pullulan has the characteristics of water-soluble, no-gelation, no-aging and without any toxicity.Pullulan is one of the few neutral water-soluble microbial polysaccharides that can be produced in large quantities by fermentation. It can be widely used in foodstuff, cosmetic, energy production and pharmaceutical industries. It can be decomposed by certain microorganisms and will not pollute the envioment. It has been studied by fermenting A. pullulans in a rotary shaker incubator and a stirred tank reacter. And a fermentation technics of pullulan's production was built. A optimized culture medium(pH6.5) of the following composition(g/L): solution of hydrolyzed cornmeal 100, yeast extract 2.0, (NH4)2SO4 0.4,K2HPO4 4.0,KH2PO4 2.0,NaCl 1.0, and MgSO4?7H2O 0.2 has been achieved. A. pullulans cells were transferred to 500ml conical flasks containing 150ml of the culture medium. The flasks were incubated at 28℃ in a rotary shaker incubator at 200rpm. And the optimized culture medium also used for the batch culture in a stirred-tank fermentor (B5) with the impeller speed of 700rpm after 500rpm for 48 hours. The batch fermentation of pullulan with A. pullulans as well as kinetics for pullulan production was studied. The mathematical kinetic models were obtained in this paper which provided a reasonable description for biomass, product and substrate variation along with the fermentation process. In the formentation of A. pullulans it would cost a lot of O2, and pullulan synthesized by the organized ferment would lead to prolonging the formentation time for stemming the productions. So it was brought forward to changing the osmosis of the cells by adding the surfacetant to the substrate. And it was found that adding Tween80(0.05%) had not only improved pullulan yield, but also shortened the formentation time. |
PDF Full Text Request