Exploration of a haloarchaeon, Halostagnicola larsenii, isolated from rock pit sea water, West Coast of Maharashtra, India, for the production of bacteriorhodopsin.

AIMS: The aim of the present investigation was to isolate haloarchaea from rock pit sea water, West Coast of India and to explore their potential in the production of bacteriorhodopsin (BR) which converts light energy into electrical energy. METHODS AND RESULTS: Haloarchaeal strains were isolated from rock pit sea water samples collected from Rock garden, Malvan, West Coast of India. Based on morphological, physiological and biochemical characteristics, and 16S rRNA gene sequencing, all the 11 strains were identified as Halostagnicola larsenii. All the strains require at least 1·5 mol l(-1) NaCl for growth; grow optimally in the range of 3·5-5·2 mol l(-1) NaCl. BR was detected in all the strains ranging from 0·035 to 0·258 g l(-1) . All 11 strains showed conversion of light energy into electrical energy in the range of 0·7-44·2 mV, when exposed to sunlight. CONCLUSIONS: A haloarchaeon, Hst. larsenii is isolated from rock pit sea water and demonstrated to have BR that converted light energy into electrical energy. SIGNIFICANCE AND IMPACT OF THE STUDY: The present investigation is presumably the first report of the isolation of Hst. larsenii from low salinity environment and its potential in production of BR. The haloarchaeon could be explored for the generation of electrical energy.

Bioremediation of nitroexplosive wastewater by an yeast isolate Pichia sydowiorum MCM Y-3 in fixed film bioreactor.

Nitroexplosives are essential for security and defense of the nation and hence their production continues. Their residues and transformed products, released in the environment are toxic to both terrestrial and aquatic life. This necessitates remediation of wastewaters containing such hazardous chemicals to reduce threat to human health and environment. Bioremediation technologies using microorganisms become the present day choice. High Melting Explosive (HMX) is one of the nitroexplosives produced by nitration of hexamine using ammonium nitrate and acetic anhydride and hence the wastewater bears high concentration of nitrate and acetate. The present investigation describes potential of a soil isolate of yeast Pichia sydowiorum MCM Y-3, for remediation of HMX wastewater in fixed film bioreactor (FFBR). The flask culture studies showed appreciable growth of the organism in HMX wastewater under shake culture condition within 5-6 days of incubation at ambient temperature (28 +/- 2 degrees C). The FFBR process operated in both batch and continuous mode, with Hydraulic Retention Time (HRT) of 1 week resulted in 50-55% removal in nitrate, 70-88% in acetate, 50-66% in COD, and 28-50% in HMX content. Continuous operation of the reactor showed better removal of nitrate as compared to that in the batch operation, while removal of acetate and COD was comparable in both the modes of operation of the reactor. Insertion of baffles in the reactor increased efficiency of the reactor. Thus, FFBR developed with baffles and operated in continuous mode will be beneficial for bioremediation of high nitrate and acetate containing wastewater using the culture of P. sydowiorum.