Pullulan production in stirred tank reactor by a colour-variant strain of Aureobasidium pullulans FB-1

Abstract

A colour-variant strain of Aureobasidium pullulans FB-1 was used for the production of pullulan in a stirred tank reactor in a medium composed of sucrose, ammonium sulphate, yeast extract, K2HPO4, NaCl and MgSO4. Maximum pullulan production (4.8%, w/v) was obtained at an agitation rate of 300 rpm and aeration of 0.75 vvm in a stirred tank reactor (1 L) with a fermentation time of 6 days. Fourier transformed infrared and NMR spectrum of crude pullulan from A. pullulans FB-1 revealed solely α-(1→6) linked maltosyl units, in accord with the generally accepted structure of pullulan. Hydrolysis of crude pullulan, i.e. digestion with pullulanase also confirmed the identity as well as homogeneity of the produced pullulan. XRD analysis of crude pullulan verified its amorphous nature. Thermal analysis showed melting range of crude pullulan from 245.99–295.71 °C.