Optimization and characterization of pullulan obtained from corn bran hydrolysates by Aerobasidiom pullulan KY767024

Abstract

Abstract In this study, corn bran hydrolysates, as an inexpensive carbon source, were used to produce the pullulan biopolymer by Aerobasidiom pullulans KY767024. The enzymatic hydrolysis of corn bran was done in the presence of α-amylase and glucoamylase enzymes and the obtained results by HPLC analysis confirmed that the glucose concentration in corn bran was significantly increased after hydrolysis process. Also, the pullulan production optimization by Box-Behnken Design showed that the maximum yield (19.45 ± 0.40 g/L) was obtained after 96 h under optimum conditions (pH 5.5, yeast extract concentration of 0.2% w/v and corn bran hydrolysates concentration of 20% w/v). The results of FTIR, H NMR and XRD spectroscopies confirmed the presence of the chemical structure pullulan in the obtained supernatant. The weight–average molecular weight of the produced pullulan was determined to be 1.22×105 gmol−1 based on the gel permeation chromatography. Besides, the thermal decomposition temperature (Td) of the obtained pullulan was ~ 280 °C showing that the resulting sample had a good thermal stability. Also, the obtained sample solution had a Newtonian flow behavior in a wide range of concentrations.