Bacterial Cellulose and Pullulan from Simple and Low Cost Production Media

Abstract

In this study, the production rate of both water-insoluble EPS, bacterial cellulose, and water-soluble EPS, P, was improved through сultivation of their producers on a nutrient media containing industrial wastes, and their material properties were analyzed. The growth rate and productivity of Gluconoacetobacter xylinus C3 strain on media with industrial wastes was investigated. An optimal nutrient medium based on molasses was selected for the bacterial cellulose producer. The nutrient medium contains 2% molasses, 1% yeast extract and peptone in a 1: 1 ratio, 0.3% sodium hydrogen phosphate, 0.1% citric acid and 1% ethanol. Cultivation of Gluconoacetobacter xylinus C3 strain on this medium for 7 days at 25–30 °С ensures its high productivity – 8.21 g/L. The composition of the optimized medium with molasses provides high mechanical properties (tensile strength – 37.12 MPa and relative elongation at break – 3.28%) of bacterial cellulose and does not affect the polymer microfibrillar structure. A modified Czapek-Dox medium with 10% molasses and 1% peptone is preferable for the exopolysaccharide accumulation by A. pullulans C8 strain. The optimized media has an advantage over the traditionally used media in terms of the efficiency of exopolysaccharide accumulation and cost reduction. The pullulan yield in media was 10.08 g/l, that is 1.5 times higher than in a standard Czapek-Dox medium. The surface morphology and microstructure of the pullulan samples obtained on different media showed minor changes. Therefore, the replacement of carbon source for molasses in a Czapek-Dox media for pullulan production did not alter the polymer content and viscosity.