Archive | 2019
Biodegradable Plastics Production by Cyanobacteria
Abstract
Commercial production of polyhydroxyalkanotes (PHAs), used as “green” thermoplastics in medicinal, fibre and agricultural field, is done by bacterial fermentation. The major drawback with bacterial system is high fermentation cost incurred due to expensive substrate and continuous oxygen supply. Therefore, in order to make PHAs production economically competitive, research efforts abound to exploit photoautotrophic hosts. In this context, phototrophic cyanobacteria are rising as a promising host for high PHAs accumulation in cytoplasm. Due to short generation time and minimum nutrient requirements, cyanobacterial cultivation is quite successful in wastewaters. Cyanobacteria accumulate high PHAs with various growth conditions, i.e. photoautotrophic, chemoheterotrophic with various carbon sources like glucose, fructose. It is evident from the recent studies that limiting nutrients supply and supplementation of excess carbon sources in the culture medium results in improved PHAs yield. Moreover, they grow better when fed with carbon dioxide, the major greenhouse gas. Therefore, utilization of cyanobacteria with wastewaters and carbon dioxide, for PHAs production seems highly promising as it has the dual advantage of polymer production and wastewaters recycling with photosynthetic utilization of CO2. This chapter presents an overview on the progresses and prospects of PHAs production from cyanobacteria. Different production strategies with nitrogen and non-nitrogen fixing cyanobacteria are discussed. Material and thermal properties of the produced PHAs are also analysed and compared with commercial polymers. This opens up the possibilities for low-cost production of PHAs polymers from cyanobacteria.