Screening Of Aureobasidium Pullulans With Reduced Pigmentation And Optimization Of Cultivation Conditions

Pullulan is an exopolysaccharide produced by Aureobasidium pullulans.This article had a research on the mutation and screening of aureobasidium pullulans with reduced pigmentation, optimization of medium and cultivation conditions, medium fermentation and the purification.Firstly, a pigment-free mutant Aureobasidium pullulans G-58 was got by UV and DES. The color of fermentation juice was milk with OD value 0.300, pH was 3.4-3.5. Pullulan production was 19.2g/L at least. According to the former result, this conclusion was received: when sugar 50g/L, MgSO40.4 g/L,(NH4)2SO4 0.4g/L, yeast extract 0.3g/L, NaCl 4g/L, K2HPO4 6g/L,inoculum time 36h, inoculum amount 2%(v/v), 28℃, the pullulan production was 23g/L ,OD is 0.04.Secondly, the medium fermentation conclusion was consilient with the former result. When the stir velocity 400 r/min air flux 3L/min, the pullulan production reached to 24.1g/L, sugar transformation rate was 48.2%.Finally, the purification conclusion was got that: after 120h fermentation, dilute the fermentation juice 5 times, centrifugal separation in 4000r/min for 30min, turn the pH value of upper liquid to 7.0, heat with 70℃for 10 min, added 3 times alcohol(95%), stirred, kept 12h at 44℃, centrifuged at 4500r/min for 15min,washed with alcohol(65%) for 3 times, centrifuged again, desiccated at 60℃, the purification production was obtained with the yield of 20g/L(89.2%). The production's purity was 95.2%. The production was white color, diffluent and similar to the standard pullulan.