Mass Cultivation and Secondary Metabolite Analysis of Rhodobacter capsulatus PS-2

Abstract

Plant growth promoting (PGP) hormones, which are produced in a small quantity by bacteria, affect in plant growth and development. PGPs play an important role on the crop productivity in agricultural field. In this study, a photosynthetic bacterial strain producing the PGP was isolated from paddy soil. Bacterial isolate was gram negative, rod-shaped and motility positive. From the 16s rRNA gene sequence analysis, the isolate was identified as Rhodobacter capsulatus PS-2. The mass cultivation of R. capsulatus PS-2 was optimized by considering of the carbon, nitrogen and inorganic salt sources. Optimal medium composition was determined as Na-succinate 4.5 g, yeast extract 5 g, K 2 HPO 4 1 g, MgSO 4 5 g , per liter. From the result of 500 L fermentation for 2 days using the optimal medium, the viable cells were 8.7×109 cfu/mL. R. capsulatus PS-2 strain produced the carotenoid and indole-3-acetic acid (IAA). The carotenoid extraction and quantitative analysis were performed by HCl-assisting method. Total carotenoid contents from R. capsulatus PS-2 culture broth were measured as 7.02±0.04 and 6.93±0.05 mg/L under photoheterotrophic and chemoheterotrophic conditions, respectively. To measure the productivity of IAA, colorimetric method was employed using Salkowski reagent at optical density 535 nm. The results showed that the highest content of IAA was 197.44 ±5.92 mg/L in the optimal medium supplemented with 0.3% tryptophan.

From Lab to Farm: Elucidating the Beneficial Roles of Photosynthetic Bacteria in Sustainable Agriculture

“…Rhodobacter capsulatus PS-2, which was isolated from paddy soil, was capable of producing a large amount of IAA (197.44 ± 5.92 mg/L) in an optimal medium containing 0.3% tryptophan. [103]. Recently, Kang and colleagues also reported that R. sphaeroides KE149 could produce 4.6-5.3 µg/mL of IAA in the presence of D-tryptophan in medium and was able to alleviate the adverse effect of water stress for adzuki bean plants [78].…”

Potential of Phototrophic Purple Nonsulfur Bacteria to Fix Nitrogen in Rice Fields

“…Among PNSB isolated from various paddy fields, R. palustris produces plant growth-promoting substances, ammonium, ALA, and indole-3-acetic acid (IAA); reduces methane emission from a mixture of soil slurry and ground rice straw; and removes Cd and Zn from the heavy metal-supplemented medium, whereas R. gelatinosus produces ammonium, ALA, and IAA and removes Cd and Zn [109]. R. capsulatus isolated from paddy soil produces carotenoids and IAA [110].…”