RESEARCH ARTICLE Chromate Reduction by Purple Non Sulphur Phototrophic Bacterium Rhodobacter sp. GSKRLMBKU–03 Isolated from Pond Water K. Rajyalaxmi 1 • Ramchander Merugu 2 • S. Girisham 1 • S. M. Reddy 3 Received: 31 May 2017 / Revised: 29 August 2017 / Accepted: 14 November 2017 Ó The National Academy of Sciences, India 2017 Abstract A purple non sulphur phototrophic bacterium (PNSB) Rhodobacter sp. GSKRLMBKU–03 was isolated from pond water of Thadoba forest, Chandrapoor District, India and its ability to reduce hexavalent chromium was discussed in the present study. Both free and immobilized cells of this bacterium were employed for chromate reduction. Immobilization of cells resulted in enhanced reduction of chromate. Sodium alginate entrapment could reduce chromate up to 40 lM, while free cells of Rhodobacter sp. GSKRLMBKU–03 could reduce about 35 lM of chromate on 8th day of its incubation under anaerobic light conditions. Both free and immobilized cells could reduce chromate even on the 20th day. Optimal growth and chromate reduction was observed on 8th day of its incubation period. The final pH of the free cells and immobilized cells in growth medium was recorded in the range of 7.5 ± 0.25–7.6 ± 0.15 at optimal incubation period respectively. The optimal growth of free cells and immobilized cells in terms of dry cell weight (DCW) was recorded as 1.80 ± 0.15 and 2.2 ± 0.20 g/L respectively. The optimal growth observed upon complete chromate reduction. The results are expressed in mean and standard deviations which are statistically significant at P B 0.05 level. The employment of Rhodobacter sp. in bioremedi- ation to detoxify chromium in large-scale systems is proposed. Keywords Chromate reduction Á Heavy metal Á Rhodobacter sp. GSKRLMBKU–03 Á Immobilization Introduction Chromium is the second most common and serious envi- ronmental inorganic pollutant widely distributed in nature. In most of the industrial waste water the chromium is available as trivalent Cr(III) or hexavalent Cr(VI) form. Hexavalent Cr(VI) is more toxic than Cr(III), which is less toxic. Microbial reduction of toxic heavy metals to less soluble non–toxic forms represents a useful detoxification process. This was shown to be of great importance in treating many types of metal containing industrial wastes [1]. Chromium has a large number of industrial applications mostly in chemical, metallurgical and refractory industries. Oxyanions of hexavalent chromium Cr(VI) have been extensively used in leather processing, finishing metal plating, corrosion inhibition, cooling tower water treat- ment, pigment manufacture, hide tanning and wood Significance statement Purple non sulphur bacterium is known for hydrogen production. In this paper, employment of Rhodobacter sp. to detoxify chromium in large-scale system is proposed with simultaneous production of biohydrogen, bioplastic, bioherbicide in a single pot. & K. Rajyalaxmi laxmi.kadari10@gmail.com Ramchander Merugu rajumerugu01@gmail.com S. Girisham sivasrigirisham@gmail.com S. M. Reddy profsmreddy@yahoo.com 1 Department of Microbiology, Kakatiya University, Warangal, Telangana 506009, India 2 Department of Biochemistry, Mahatma Gandhi University, Nalgonda, Telangana 508254, India 3 Department of Botany and Microbiology, Kakatiya University, Warangal, Telangana 506009, India 123 Proc. Natl. Acad. Sci., India, Sect. B Biol. Sci. https://doi.org/10.1007/s40011-017-0939-8