Novel application of oligosaccharides as elicitors for the enhancement of bacitracin A production in cultures of Bacillus licheniformis

This work reports, for the first time, oligosaccharides as elicitors enhancing production of bacitracin A in liquid cultures of Bacillus licheniformis. A 33 fractional factorial design was used to investigate optimal elicitation conditions. Mannan oligosaccharide moiety (MO), oligomannuronate (OM) and oligoguluronate (OG) were used as elicitors with concentrations of 100, 200 and 300 mg/L and addition times of 0, 12 and 24 h. There was enhancement of bacitracin A production with no significant change in biomass levels using the oligosaccharides as elicitors. Supplementation of B. licheniformis liquid cultures with mannan oligosaccharide moiety and oligomannuronate resulted in similar bacitracin A titres of up to 782 mg/L after 52 h. Response surface methodology, showed statistically significant effect on the cultures by the elicitor type (P < 0.0001) and concentration (P < 0.005). The final optimal condition for highest bacitracin A production was 100 mg/L of OG added to 24 h old cultures. Overall, OG was found to be the most effective elicitor with bacitracin A yield significantly different compared to the control (P < 0.5). Yield improvements of 29%, 27% and 16% over the control were achieved with OG, MO and OM, respectively.