Production and characterization of polyhydroxybutyrate from Vibrio harveyi MCCB 284 utilizing glycerol as carbon source.

AIMS: Production and characterization of polyhydroxybutyrate (PHB) from moderately halophilic bacterium Vibrio harveyi MCCB 284 isolated from tunicate Phallusia nigra. METHODS AND RESULTS: Twenty-five bacterial isolates were obtained from tunicate samples and three among them exhibited an orange fluorescence in Nile red staining indicating the presence of PHB. One of the isolates, MCCB 284, which showed rapid growth and good polymer yield, was identified as V. harveyi. The optimum conditions of the isolate for the PHB production were pH 8·0, sodium chloride concentration 20 g l-1 , inoculum size 0·5% (v/v), glycerol 20 g l-1 and 72 h of incubation at 30°C. Cell dry weight (CDW) of 3·2 g l-1 , PHB content of 2·3 g l-1 and final PHB yield of 1·2 g l-1 were achieved. The extracted PHB was characterized by FTIR, NMR and DSC-TGA techniques. CONCLUSIONS: An isolate of V. harveyi that could effectively utilize glycerol for growth and PHB accumulation was obtained from tunicate P. nigra. PHB produced was up to 72% based on CDW. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of an isolate of V. harveyi which utilizes glycerol as the sole carbon source for PHB production with high biomass yield. This isolate could be of use as candidate species for commercial PHB production using glycerol as the feed stock or as source of genes for recombinant PHB production or for synthetic biology.

DNA sequence information resolves taxonomic ambiguity of the common mud crab species (Genus Scylla) in Indian waters.

For several years, mud crabs of genus Scylla have been misidentified owing to their high morphological plasticity and the absence of distinct morphological diagnostic characters. The taxonomic confusion of genus Scylla de Haan is considered to be a primary constraint to the development of aquaculture. Although genus Scylla was revised using morphological and genetic characteristics, taxonomy of Scylla species occurring in India is still not clear. In this study, partial sequences of two mitochondrial genes, 16S rRNA and CO1 (Cytochrome C oxidase subunit I) in populations of Scylla spp. obtained from eleven locations along the Indian coast were used to differentiate and resolve taxonomical ambiguity of the mud crab species in India. The sequences were compared with previously published sequences of Scylla spp. Both trees generated based on 16S rRNA and CO1 indicated that all S. tranquebarica morphotypes obtained during this study and S. tranquebarica sequences submitted previously from Indian waters reciprocally monophyletic with reference sequence of S. serrata. Both sequence data and morphological characters revealed that the species S. serrata (Forskal) is the most abundant followed by S. olivacea. Further, the 16S rRNA and COI haplotypes of Indian S. tranquebarica obtained in the study significantly differed with the known S. tranquebarica by 6.7% and 10.6% respectively whereas it differed with known S. serrata by 0.0-0.7% only, a difference that was not statistically significant. From these studies it is clear that "S. tranquebarica" commonly reported from India should be S. serrata (Forskal).