Determination of antimicrobial activity and production of some metabolites by Pseudomonas aeruginosa B1 and B2 in sugar beet molasses

In the present study, exopolysaccharide (EPS), pyocyanin, rhamnolipid productions, total cell proteins and antimicrobial activities were investigated in two strains of Pseudomonas aeruginosa (B1 and B2). Exopolysaccharide, pyocyanin and rhamnolipid production of strains were determined in nutrient broth medium (NB) as control and different sugar beet molasses concentrations (1-5 % w/v) at different periods (24, 48 and 72 h) by a spectrophotometric method. The exopolysaccharide, pyocyanin and rhamnolipid productions of both strains increased after incubation when 5% (w/v) of molasses were used. Therefore the results disclose the correlations between the increasing molasses concentrations and EPS, pyocyanin and rhamnolipid productions of P. aeruginosa B1 and B2 strains (P≤ 0.01). Bacillus subtilis ATCC 6633 was more sensitive than Escherichia coli 11230 to the inhibitory effect of P. aeruginosa B1 and B2. Moreover, these strains exhibited the highest antimicrobial activity against both test bacteria in sugar beet molasses (5% w/v) at 72 h. Significant increases in total cell protein and antimicrobial activity of P. aeruginosa B1 and B2 were observed with increasing the molasses concentrations (P≤ 0.01). The results also indicated that strains having high total cell protein were higher antimicrobial activity, EPS, pyocyanin and rhamnolipid productions.