Optimization of Exopolysaccharide Production by Bacteria Strains Isolated from Brewery Wastewater Sludge collected from a Brewery Company in Uyo, Akwa Ibom State, Nigeria

Abstract

Bacteria make expolysaccharides (EPS) in two basic forms; as firmly attached capsular-EPS and loosely attached slime-EPS. Hence, the objective of this paper was to investigate the optimization of exopolysaccharide (EPS) production by bacteria strains isolated from brewery wastewater sludge collected from a Brewery Company in Uyo, Akwa Ibom State, Nigeria using random mutagenesis. Bacterial isolates from brewery wastewater sludge samples were screened for EPS production using standard microbiological method. Six (6) best EPS-producing bacterial isolates were selected, identified molecularly as Bacillus altitudinis, Bacillus velezensis, Bacillus subtilis, Pseudomonas aeruginosa, Heyndrickxia oleronia, and Acinetobacter calcoaceticus, and used for optimization of EPS production after exposure to UV-irradiation and ethidium bromide (EtBr). In all the isolates, UV-irradiation caused the production of significantly (P<0.05) higher EPS yield than EtBr. However, both treatments induced the formation of mutant strains with higher EPS yields than the wild strains. The quantity of EPS produced varied among the mutant strains and ranged from 0.46±0.02 g/100ml in EtBr-mutant strain EPBS.6 to 0.86±0.01 g/100ml in UV-mutant strain EPBS.1, indicating 15.1% to 26.5% yield increase compared to the wild strains with EPS yields of 0.40±0.02 g/100ml to 0.68±0.01 g/100ml. Previous studies have reported Bacillus altitudinis, Bacillus velezensis, Bacillus subtilis, Pseudomonas aeruginosa, and Acinetobacter calcoaceticus as EPS-producers, but little or no known report was on ground regarding EPS producing capacity of Heyndrickxia oleronia, sufficing that it might be a novel EPS-producing bacteria strain. Based on these results, we therefore conclude that the bacteria strains obtained have the potential to produce EPS and the production can be improved through random mutagenesis with UV-irradiation and EtBr. We recommend brewery wastewater sludge as a rich source of novel EPS-producing bacteria and suggest further study on the mechanism of mutagenesis on EPS production by bacteria.

Keywords

• Optimization, exopolysaccharide production; bacteria; mutagenesis; brewery wastewater sludge