Laxuman Sharma

Poly‐β‐hydroxybutyrate accumulation in cyanobacteria under photoautotrophy

Poly-β-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-β-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.

Enhancement of poly-β-hydroxybutyrate accumulation in Nostoc muscorum under mixotrophy, chemoheterotrophy and limitations of gas-exchange

Nostoc muscorum, a heterocystous cyanobacterium, produced poly-β-hydroxybutyrate ( PHB) up to 8% (w/w) dry cells when grown photoautotrophically but 35% when grown mixotrophically with 0.4% (w/v) glucose and acetate after 21 d. Gas-exchange limitations under mixotrophy and chemoheterotrophy with 0.4% (w/v) acetate enhanced the accumulation up to 40–43% (w/w) dry cells, the value almost 5-fold higher with respect to photoautotrophic condition.