Study On Fermentation Conditions And Glycolytic Pathway Of Aureobasidium Pullulans

Aureobasidium pullulans is a yeast-like fungus with complex life cycle, the change of its morphological forms is affected by many factors. In suitable conditions, the strain of Aureobasidium pullulans produces a major polysaccharide—Pullulan. The pullulan has been widely used in many fields owing to its characteristics of water-soluble, no-gelation, good thermo stability, viscosity stability, and pollution-free.This study chose metabolism characteristic in A.pullulans G-58, a laboratory mutants, as a model system to build and optimize the cultural conditions by the dialysis cultivation. Based on this work, the effect of different fermentation substrates and glycolytic pathway of G-58 was studied. The main results were described as follows:①Optimize the cultural conditions of Aureobasidium pullulans G-58: bacterial suspension by dialysis cultivation was easy for controlling inoculum size. OD600 of bacterial suspension 0.442, the inoculation time 36 h, fermentation temperature 28℃, initial pH 7.0, 250 mL shake flask containing 50 mL of sucrose medium and shaking revolution 200 r/min. Under these conditions, the highest pullulan yield with the lowest pigment was obtained; the reproducibility of fermentation in batches was good, the stability of experiments effectively was improved.②The effects of different fermentation substrates on G-58: the effects of different carbon and nitrogen sources on A. pullulans G-58 growth, pullulan production and the morphological forms were studied. A. pullulans G-58 grow in glucose and sucrose media produced the highest pullulan yield with the lowest pigment; the organic nitrogen sources were better than inorganic and the composite nitrogen sources were better than single. Yeast extract and (NH4)2SO4 as nitrogen sources had good effect on pullulan yield. The morphological forms of A.pullulans G-58 with high pullulan yield were predominantly chlamydospores and swollen cells③The effects of inhibition on glycolytic pathway of A. pullulans G-58: Pullulan production by A. pullulans G-58 was used as a model for investigating the effects of glycolytic inhibiton on the two key enzymes. The study showed glycolytic inhibiton affect the biomass and the pullulan yield of A.pullulans G-58 on certain level. It could predicate the growth of A. pullulans G-58 based on EMP, EMP and HMP acted together on the glycolytic pathway. The increase of metabolic flux of HMP could promote the growth of A. pullulans G-58, and the polysaccharide biosynthesis was mainly relied on EMP.