Azotobacter was selectively isolated and purified from the soil samples of Xinjiang Salt Lake Scenic spot, the fermentation technology of exopolysaccharides (EPS) by Azotobacter was optimized, and the antioxidant activity of exopolysaccharides (EPS) was studied. The bacteria were isolated and purified from the soil samples by the scribing method and the 16SrRNA gene was used for molecular identification. The carbon source, fermentation time, inoculation amount and pH of target bacteria in the exopolysaccharides (EPS) fermentation process were optimized through single-factor experiments and their antioxidant activity was measured. Eight types of Azotobacter were isolated and purified from the soil samples of Salt Lake scenic spot. Among them, As101, which showed 99.58% homology with Azotobacter salinestris, was selected as the target strain. Through single-factor experiments which used exopolysaccharides (EPS) yield and exopolysaccharides content as indexes, the optimal conditions for the As101 fermentation process were determined as follows: fermentation temperature 35, fermentation time 96h, pH 7 and mannitol as carbon source. Exopolysaccharides content from Azotobacter salinestris  was 61.35% and the yield was 6.34 g/L. The results of the exopolysaccharides (EPS) antioxidant activity experiment under optimal conditions showed that As101 EPS had excellent scavenging ability against DPPH free radical, ABTS free radical and hydroxyl free radical, with IC50 values of 6.11 mg/ml, 2.42 mg/ml and 9.57 mg/ml, respectively. As101 with high yield and high exopolysaccharides content was isolated from saline soil in a special environment of Xinjiang, and the EPS obtained showed excellent antioxidant activity. The Azotobacter found in this study would provide the material basis for further opening up the adsorption of exopolysaccharides on heavy metals and the improvement of saline-alkali soil and contribute to further understanding of the structure and other activities of exopolysaccharides derived from Azotobacter.

Okra is an herbaceous hairy annual plant that belongs to the family Malvaceae. It is cultivated in tropical, subtropical, and warm temperate regions around the world. The present work was carried out to study the effect of biofertilizers (Azotobacter + Bacillus) and different concentrations of Nitrogen, Phosphorus, and Potassium i.e.NPK on growth and photosynthetic pigments of okra (Abelmoschus esculentus L. Moench). Okra can be named a multipurpose crop as its various parts such as leaves, buds, flowers, pods, stems and seeds can be used for different purposes [1]. Okra is rich in dietary fiber, vitamins, oils, etc. Application of hazardous fertilizers causes a nutrient imbalance in soil, With respect to reducing the causes due to chemical fertilizers, biofertilizers are suited best to maintain higher productivity and yield of crops. Random block design (RBD) was selected as an experimental design. The treatments combination taken are T0- Control, T1- Azotobacter + 50% NPK, T2- Azotobacter (2.5 kg/ha) + 100% NPK, T3- Bacillus (2.5 kg/ha) + 50% NPK, T4- Bacillus (2.5 kg/ha) + 100% NPK, and T5 with NPK 100%. The final result revealed, that the treatment combination with Azotobacter + 100% NPK (T2) showed the highest value of plant height (65.60 cm), number of leaves per plant(62.36), number of flowers per plant (27.40), and also carotenoid content (2.82 mg/g), chlorophyll a(2.47 mg/g) and chlorophyll b(3.25 mg/g) were observed maximum. So, it can be concluded through this paper that the combination of Azotobacter 2.5 kg/ha + 100% NPK (T2) is suitable for the okra plant for better growth and enhancement of photosynthetic potential in-field practices.