Understanding response surface optimization of medium composition for pullulan production from de-oiled rice bran by Aureobasidium pullulans.

Central composite rotatable design of RSM was used for the optimization of medium composition for pullulan production from de-oiled rice bran by Aureobasidium pullulans in shake-flask fermentations. The sugars from de-oiled rice bran were extracted in distilled water under moist steam pressure and the obtained de-oiled rice bran extract (DRBE) was used for the optimization of medium composition. RSM optimized medium components (DRBE sugars, 3.88%; yeast extract, 0.24%; (NH4)2SO4, 0.06%; K2HPO4, 0.57% (w/v), and pH, 5.22) supported 5.48% (w/v) pullulan production and 0.88 (A600/100) biomass yield. Coefficient of determination for pullulan production (0.99) and biomass yield (0.99) was close to 1.0 which justifies significance of model. Lack of fit for both responses was non-significant, which shows fitness of quadratic model. FTIR and NMR spectral attributes confirmed the structure of pullulan. XRD patterns verified the amorphous nature of pullulan. De-oiled rice bran was found as a potential substrate for pullulan production. © The Korean Society of Food Science and Technology 2019.