Isolation and Characterization of Phb Producing Micro-organisms Isolated from Root Nodules of Leguminous Plants

A number of the micro-organisms are capable of producing polyhydroxyalkanoates (PHA’s) as storage food reserve under unbalanced growth conditions. The mechanical properties of PHA’s are similar to that of synthetic plastics like polyethylene, polypropylene etc. The advantage of using PHA’s over synthetic plastic is that PHA’s are completely mineralized into carbon dioxide and water through the action of various microorganisms. Polyhydroxybutyrate (PHB), Polyhydroxybutyratecohydroxyvalerate (PHBV) are the best known representatives of PHA family. These representatives of PHA can be used to produce environment friendly alternative to the synthetic polymers which pose a number of environmental problems. PHB are produced intracellularly by various organisms such as Bacillus megaterium, Ralstonia eutrophus, Cupriavidus necator, Rhizobium spp., Azotobacter spp., Pseudomonas spp., etc under physiological stress conditions. These bacteria can accumulate up to 60-80% of their weight as PHB under limiting nitrogen substrate and in the presence of an abundant source of carbon (Anderson and Dawes, 1990). In last few years, various attempts have been made to use PHB for the production of biodegradable plastics (bioplastic) (Mercan, 2002; Mukherjee et al., 2011). The major limitation in the use of biodegradable plastic is their high cost as compared to the synthetic plastic. It is well established that the cost of production of any microbial product can be reduced significantly if these micro-organisms are harvested on low cost media having agro-industrial byproducts since media is the main component that add to cost of production (Dhingra, 2012; Goyal and Dhingra 2011).