Application of classical mutation and selection method for isolation of xanthomonas citri subsp.citri (xcc) mutants with capability to produce more xanthan gum

Xanthomonas citri subsp. Citri is a gram – negative bacterium casual agent of citrus canker disease. The bacterium also produces acidic heteropolysaccharide called xanthan. Xanthan gum is one of the most popular biochemical agents, widely used as stabilizer, emulsifier and suspender in many industries including cosmetics food, texitiles, drug and petroleum etc. This is mainly because of high viscosity characteristic of xanthan. Bacteria belonging to Xanthomonas genus are capable to produce this exopolysaccharid in glucose and sucrose containing media. In spite of, Xanthomonases not to capale to consume lactose-base culture, but Xanthomonas citri has a specific ability to consume lactose- base culture including whey, naturally. Therefor, Xanthomonas citri is purpose of this research. The purpose of this investigation is a using mutation and selection technics to creat Xanthomonas citri subsp.citri (Xcc) mutants with capability to producing more xanthan gum. In this study, a series of mutants were isolated from Xanthomonas citri k37 by classical mutagenesis, after using mutageneis agents for instance, UV and nitrouse acid, screening of different mutants was accomplished. Initial screening was based on the enhanced diameter of the colonies in comparison with that of the wild strain on lactose containing agar medium. Among numerous screened colonies, twenty mutants with colony diameter bigger than the parental strain, were isolated. At the next step, xanthan production and the viscosity of mutants was compared with that of the parental strain in production medium. In conclusion, among 20 screened mutants, 2 mutants, which produced 37.68 and 33.46 g/l xanthan gum that these values is more than of native strain, with production level of 27.9 g/l.

کلیدواژه ها:

xanthan gum ، xanthomonas citri subsp. Citri ، mutation and selection ، ultra violent ، nitrous acid