MICROBIAL POLYSACCHARIDE PRODUCTION

Polysaccharides belong to the group of carbohydrates and are polymers made up of monomers linked by O-glycosidic bonds. They can be obtained by extraction processes, whose synthesis occurs directly from plant sources or through fermentation processes, in which biosynthesis occurs from microorganisms. Considering the latter, it is possible to find them in the intracellular form (they provide energy to the cell and act as a carbon source) or extracellular form (the polysaccharides are excreted in the extracellular environment), these are known as exopolysaccharides (EPS). The EPS are of great industrial interest, since they have important ecological and physiological functions, as they protect microorganisms from unfavorable conditions, such as: action of antimicrobial substances of bacterial origin, desiccation, bacteriophages, osmotic stress, antibodies, selectivity to the diffusion of nutrients to the inside or outside of the cell and also adhere to the solid surface for biofilm formation. Therefore, the objective of this work was to produce EPS using different carbon sources, such as: fructose, glucose, lactose and sucrose. In advance, the microorganism called LBA-814 was inoculated in petri dishes containing Yeast Malt Medium – YM (%): bacteriological peptone 0.5; carbon source (glucose) 1; yeast extract 0.3; agar 2; distilled water previously solidified for 48 hours at 30 °C in a bacteriological oven. Subsequently, three layers of bacterial culture were added to Erlenmeyer flasks containing 100 mL of submerged YM. In this step, the carbon source was varied (fructose, glucose, lactose and sucrose) and the other components were maintained. These were incubated in a refrigerated incubator with shaking for 120 hours at 30°C and 150 rpm. Every 24 hours of the process, 3 mL aliquots were withdrawn to check the EPS production. For this, the samples were centrifuged at 3000 g for 12 minutes, to separate the biomass from the supernatant. Then, EPS precipitation was performed by adding ethyl alcohol at 4°C (1:3 v.v -1) to the supernatant. Subsequently, the mixture was conditioned for 24 hours at 5°C. After this time, the mixture was centrifuged again and subsequently dried in an oven at 45°C until constant mass. Statistical treatment was performed using the Statistica 7.0 software. As a result, it was observed that the carbon sources studied had a positive effect on EPS production. The highest production was observed using sucrose (6.71 g/L), followed by glucose (5.05 g/L), lactose (3.27 g/L) and fructose (2.87 g/L) with 120 hours of fermentation process. However, sucrose was the source with the best production, in addition, it showed a significant difference (p-value<0.05) in relation to the other sources studied. Thus, it is concluded that the evaluation of carbon sources made it possible to find the source with the best assimilation and production of EPS, from the LBA-814 lineage. Therefore, sucrose as a source is already widely explored in industries for different fermentation processes, especially for the production of EPS.