EXOPOLYSACCHARIDE SYNTHESIS BY Bacillus thuringiensis HA1 USING CARBON SOURCES FROM THE SUGARCANE AGROINDUSTRY

Abstract

Exopolysaccharides are biopolymers produced by bacteria and have characteristics that make them suitable for applications in the pharmaceutical, environmental, and food industries. However, exopolysaccharide production faces challenges like high production costs. Therefore, strategies such as culture conditions improvement, strain selection, and the use of low-cost carbon sources have emerged as alternatives to improve exopolysaccharide production. In this work, the capability of Bacillus thuringiensis HA1 to produce exopolysaccharides using low-cost carbon sources (commercial sucrose, molasses, and panela) was explored. The production conditions were evaluated as follows: fermentation time (0–86 h), initial pH (5–9), temperature (31–43 °C), carbon sources (commercial sucrose, molasses, and panela), and concentration of carbon sources (50–350 g L^-1). The settled conditions to assess the carbon sources were 60 h, 37 °C, and pH 7.5. Exopolysaccharide production was higher using commercial sucrose (23.54 mg mL^-1), followed by molasses (8.62 mg mL^-1) and panela (6.37 mg mL^-1). The sucrose sample showed similarity to a glucan-type exopolysaccharide, since the presence of peaks at 1000–1200 is characteristic of C–O–C glycosidic linkages, while the molasses sample showed similarity to the standard levan. These results were achieved without pretreating the carbon sources, thus allowing the process to be economically feasible. To date, Bacillus thuringiensis has not been reported as a producer of two types of exopolysaccharides using different carbon sources.