Evaluation of alginate production by native strains of Azotobacter isolated from soil by carbazole reagent by Nutson-Jeans method

Background and Aim : production of alginate through microbial biotechnology has become important due to the reduction of production time and costs and also the damage to the marine ecosystem due to the uncontrolled extraction of alginate from marine kelps. Azotobacter are a better choice for producing alginate than pathogenic Pseudomonas. we have tried to evaluate the ability of alginate to produce native isolates of Azotobacter from the soil by the Nutson-Jeans method and finally spectrophotometry.Methods : Azotobacter strains were monitored and purified through differential cultures. Each strain was inoculated into mannit broth and incubated at ۳۷ ° C for ۴۸ hours. Alginate production was evaluated by carbsol reagent test using Nutson-Jane method at two temperatures of ۵۵ ° C and ۱۰۰ ° C in borate and non-borate conditions. Finally, by spectrophotometry at ۵۲۰ nm with two repetitions of positive and negative control of culture tubes were examined.Results : The culture tubes of the carbazol reagent test stage had a pink to purple color spectrum that indicated the presence of alginate produced by native Azotobacter. Increasing the color spectrum from pink to red and finally purple indicated an increase in alginate production.Conclusion : This study showed that native Azotobacter isolated from soil have the ability to produce alginate, which carbazol reagent test along with spectrophotometry was able to prove their ability to produce alginate.