Optimization of Soil Bacteria for Bioplastic Production Using Organic Wastes as a Substrate Under Submerged Fermentation

Abstract

In the perspective of the threats to environment associated with petroium-derived synthetic plastics, there is a critical need to traverse biologically degradable polymeric material. Biologically synthesized polyhydroxyalkanoates are the most promising candidates to be used as bioplastic. Keeping in view the ecofriendly nature of bioplastics, the current study was designed to explore contaminated soil samples for bioplastic producing bacterial strains and use organic wastes as a sole carbon source to reduce cost of bioplastic production. Contaminated soil samples from various areas of Peshawar, Charsada and Dargai were screened for bioplastic producing bacterial strains by using primary stain Sudan black and confirmatory stain Nile blue A. The growth medium and physical parameters were optimized for efficient producers. A variety of organic wastes; fruits and vegetable wastes were used as carbon source in E2 medium under submerged fermentation in 1L flasks for bioplastic production by optimized higher yielding bacterial strain KHA-S-03. E.coli K12 and Ralstonia eutropha MTCC1285 were used as negative and positive control respectively. KHA-S-03 was molecularly identified to be Bacillus megaterium SFK by 16srDNA sequencing and Pha C gene of identified strain was sequenced and phylogenetically analyzed, this strain was able to utilize organic wastes as sole carbon source under optimized condition of incubation time 48 h, pH 7, temperature 37 °C, substrate concentration 5%, C/N ratio 8:1, agitation rate 200 rpm, inoculum size of 5% and nitrogen sources (NH4)2SO4 and NH4Cl. For efficient downstreaming, among various solvents tested, ethylene carbonate (nontoxic solvent) was found to have efficiency near to chloroform (toxic solvent).