Chemical Mutagenesis for Improvement of Production of a Biologically Active Extracellular Polymeric Substance by Halomonas xianhensis SUR308

A moderately halophilic bacterium, Halomonas xianhensis SUR308 (Genbank Accession No. KJ933394) isolated from solar saltern of Surala, Odisha, India was found to produce significant amount of a biologically active extracellular polymeric substances (EPS). Under optimized cultural conditions, the strain was able to produce 7.05 g L^-1 of EPS after 8 days of incubation under shake culture. To enhance the EPS production efficiency, the isolate SUR308 was subjected to chemical mutagenesis following the use of hydroxylamine (HA), acridine orange (AO) and ethyl methanesulfonate (EMS). Evaluation of the toxicity of these mutagens indicated that EMS was comparatively toxic but effective for mutagenesis. Mutagenic treatments have resulted in the isolation of 58 amoxycillin resistant morphologically distinct phenotypes. Three of these mutant phenotypes (EM3, EM13 and HM6) were capable of producing 12.98, 11.97 and 11.21 g L^-1 of EPS respectively in malt extract-yeast extract medium supplemented with casein hydrolysate with significant reduction of incubation  period. Compared to wild type strain, mutant strains were found to produce 1.6-1.8 fold more EPS. However, the physico-chemical nature of the EPS derived from the mutants remained unaltered when compared with that of the wild type strain. These findings, therefore, have more impact on production economy of EPS for biotechnological applications.