Screening and isolation of lactose – consuming strains of Xanthomonas citrisubsp citri (Xcici) to use in whey containing medium

Xanthomonas citri subsp. Citri (Xcici) is a gram –negative bacterium and casual agent of citrus cankerdisease .This bacterium also produces an acidic heteropolysaccharide called xanthan. Xanthan gum is oneof the most popular agents, widely used for stabilizing, emulsifying and suspending in many industriesincluding petroleum, textiles, food and etc. That is due to high viscosity and its other uniquecharacteristics. These bacteria are able to produce xanthan in glucose and sucrose media. Due to low of β-galactosidase activity in Xanthomonas bacteria, they cannot use lactose an consequently are able toproduce a little xanthan in lactose basic medium. Whey is a dairy byproduct and a rich source lactose andprotein, which can be used as a cheap and suitable substrate containing lactose, in xanthan productionindustries. In this research, we screened bacterial strains of Xcici collection existing in NIGEB for abilityto use lactose. Then we applied molecular methods for cloning of 16srDNA gene of bacterium andsequencing. Recently, was measurement number of strains viscosity in YMB maintains medium.

Keywords:

xanthan , Xanthomonas , β- galactosidas , whey