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.

Production of copolymer, poly (hydroxybutyrate-co-hydroxyvalerate) by Halomonas campisalis MCM B-1027 using agro-wastes.

For cost effective production of PHA, agro-wastes like fruit peels, bagasse and deoiled cakes were screened as a sole source of carbon. Halomonas campisalis MCM B-1027, which was isolated from one of the extreme environment, i.e. Lonar Lake, India, was explored for the production of PHA using fruit peels and bagasse having fermentable sugars. Among the agro-wastes tested, 1% (v/v) aqueous extract of bagasse was found to be the optimum carbon source with 47% PHA production on dry cell weight basis. Significant amount of total sugars are utilized and converted into cell mass and PHA, e.g. 62% sugar utilized from bagasse extract, 84% from orange peel extract and 71% from banana peel extract as compared to 51% in case of maltose. Hence the cost of production would be positively reduced. The detailed characterization of PHA formed by H. campisalis using bagasse extract as sole carbon source revealed that the organism produces a copolymer of PHB-co-PHV (94.4:5.6) having molecular weight M(w) 1.394 × 10(6) and melting temperature 168.9 °C. Production of PHA by H. campisalis using aqueous extract of fruit peels and a copolymer PHB-co-PHV using aqueous extract of bagasse is presumably the first report.

Production and characterization of a biodegradable poly (hydroxybutyrate-co-hydroxyvalerate) (PHB-co-PHV) copolymer by moderately haloalkalitolerant Halomonas campisalis MCM B-1027 isolated from Lonar Lake, India.

Several microorganisms produce polyhydroxyalkanoates (PHA). They are accumulated intracellularly as energy storage compounds. The PHAs are of interest because of their potential in biomedical applications. Halophilic bacteria and archaea are known to produce polyhydroxybutyrate (PHB). This paper describes production of a biodegradable copolymer, PHB-co-PHV by a moderately haloalkalitolerant Halomonas campisalis, isolated from Lonar Lake, India. The production of PHA was in the range of 45-81% on dry cell weight basis when the organism was grown in a production medium containing 1% (w/v) maltose and 0.1% (w/v) yeast extract, at pH ranging from 6 to 9 with an inoculum density of 10(5)-10(7) cells/ml of medium, for incubation period of 15-30 h and at 37 degrees C. The polymer produced by the organism is a hydroxyester with molecular weight of 1.3014 x 10(6). Its melting temperature was 171 degrees C. The (1)H NMR analysis revealed that the polymer was a copolymer of PHB-co-PHV. This could be achieved by providing simple carbon source viz. maltose.