Poly-ß-hydroxybutyrate accumulation in cyanobacteria under photoautotrophy.

Poly-ß-hydroxybutyrate (PHB) is a biodegradable and biocompatible polymer that has immense potential in the field of environmental, agricultural and biomedical sciences. An alternative host system has been explored in this study for low-cost production. Examination of 25 cyanobacterial species from 19 different genera for photoautrophic production of polyhydroxyalkanoates (PHAs) under batch culture demonstrated that 20 species were poly-ß-hydroxybutyrate (PHB) accumulators, while others were found to be negative. Presence of PHB was confirmed by UV-spectroscopy, (1)H-NMR spectroscopy and GC-MS analysis. Accumulation of PHB in cyanobacteria was found to be species specific. The PHB extracted from Nostoc muscorum exhibited comparable material properties with the commercial PHB, thus advocating its potential applications in various fields.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) co-polymer production from a local isolate, Brevibacillus invocatus MTCC 9039.

Accumulation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] co-polymer by a local isolate, Brevibacillus invocatus MTCC 9039 under batch mode was investigated under glucose, acetate and propionate-supplemented conditions. Cells harvested at the stationary phase of growth depicted maximum accumulation of poly-3-hydroxybutyrate (PHB), i.e. 3% of dry cell weight (dcw) at pH 7.0 and temperature 30 degrees C at 48h of incubation. PHB accumulation reached up to 52% (dcw) under 3% glucose with 1% acetate supplementation. P(3HB-co-3HV) co-polymer synthesis was observed under propionate-supplemented condition, which reached up to 45% under 3% glucose with 1% propionate supplementation. Optimization of process parameters by response surface methodology (RSM) resulted into co-polymer accumulation up to 65% (dcw) at 2.08% glucose, 1.62% acetate, 0.75% propionate and 2.15 g l(-1) KH(2)PO(4) concentrations. This co-polymer exhibited comparable material properties with the commercial [P(3HB-co-3HV)] co-polymers, whereas the elasticity was tremendously high and could be comparable with polypropylene. Thus, B. invocatus MTCC 9039 is emerging as an interesting organism and could be exploited further for P(3HB-co-3HV) co-polymer production.