Study On Fermentation Of Aureobasidium Pullulans Polysaccharide

Pullulans polysaccride, produced from aureobasidium pullulans, is a kind of extracellular polysaccride. Because of its excellent properties such as easy fabrication of film and fibre, good cohesivness, easy biodegradation, and oxygen permeation proof etc., pullulans, a new type of biological materials, has a wide application in pharmacy production, food industry and cohesivness of fruits, vegetables and seafood. Lots of scientists and enterprisers in the world focus on it, but its synthetic mechanism of polysaccride is still unknown, and there are different reports about its industrial ferment. In the process of fermenting, aureobasidium pullulans can produce various pigments, such as black pigments, brown pigments, and green pigments, etc., which pollute the polysaccride. On the other hand, more steps to decolor and filter active carbon can lead to the fall of yield and the lower ability for colourless strains to produce polysaccride. So the report about colourless strains applied to industial production hasn't been seen up to now.In this paper, we abide the procedure of from primary strains to flask fermentation to magnifying for cultivation. First, rejuvenate and pick up the long-term keeping strain; then, focus on flask fermentation, in the course of which the following aspects should be stressed: 1. By changing the ion concentration, infiltration pressure of mediums and adding to surface active reagent, we try to influence the permeation character of cell membrane, which can promote the exchange of inside substances of cell membrane with the outside ones, and improve the profitability of mediums. Thus, there is a prominent impact on the improvement of the decentralization degree and yield of polysaccride by adding tween-80, which can solve the problem of macelium mass; As to the application of Ca2+, we replace CaCl2 with CaCO3, which has a very low dissolvability, to release Ca2+ and balance pH of fermenting medium. 2. In order to get the best formula for sucrose, K2HPO4, (NH4)2SO4 yeast extract and CaCO3, a five-factor and four orthogonal test was designed, and a high conversion rate of 70% and pullulan yield 35.0g/L were obtained from the medium with initial 5% sucrose. 3. The fermenting conditions such as initial PH, volume, inoculability quantity etc. were studied, and the optimum conditions have been found.At last, we study the magnifiying for cultivation by adopting Biostat?B 5L according to the optimum formula, and find the optimum aerat speed is 1.5wm, and the rate of circle is 500rpm and culture temperature is 28℃ ± 1.5℃, and initial pH is 6.5, so a high conversion rate of 60% was obtained from the light colour medium.The study conducted in this paper can lay a good foundation for applying colourless strain to industrialized production, and offer some references to studying the mechanism of producing polysaccride.