K. S.JAGADEESHCHANDRASHEKHARAIAH P. S.2019-06-202019-06-202007-08-30TH8733http://krishikosh.egranth.ac.in/handle/1/5810109316In the present study, an attempt was made to isolate efficient PHB producing bacteria from different environmental samples. A total of eight samples were collected and 656 bacteria were isolated and 24 bacteria were collected from the Departmental culture collection. Out of these, 101 were found to be PHB positive based on viable colony staining method using Sudan Black B. All the 125 PHB positive isolates were subjected to quantitative estimation of PHB production. PHB jdelds varied from 0.010 to 0.160 g/100 ml. Ten promising bacterial isolates were selected based on their PHB yields. They were EJC2, EJC5, KJC7, NJC3, FJC4, MJCIO, TJCl, BJC7, B25 and DJC6. The culture parameters were optimized for all the 10 isolates. Glucose was found to be the best carbon source for maximum PHB production by all the isolates. Ammonium sulphate supplementation at 0.1 per cent was found to be optimum. Maintaining the C:N ratio of 20:1 using the best C and N source was found to be optimum. Maintaining the pH of the medium at 7.0 was found optimum. In order to reduce the cost of PHB production.whey and waste water of a soft drink industry were tested as cheaper substrates. Although they supported PHB production, the yields were rather low when compared to those on standard media. However, the jdelds could be improved to some extent, by supplementation with glucose at 1 per cent level. But, the advantage is that the biowastes can not only be disposed off but also value added product like PHB can be obtained. DJC6 reduced COD of whey by 43 per cent, thus functioning as a bioremediating agent. Out of ten natural promising isolates, DJC6 and BJC7 were found to be the most efficient PHB producers. Under optimized conditions, DJC6 produced a PHB jdeld of 1.100 g/100 ml while BJC7 produced 0.85'90 g/100 ml. DJC6 performed better than the reference strain R. eutropha in PHB production. DJC6 and BJC7 were tentatively identified as Bacillus spp. and Pseudomonas spp. respectively, based on the morphological and biochemical tests. Scale up studies in 3 litre bottle fermenters were conducted under the optimized conditions. Pseudomonas sp. DJC6 produced a PHB yield of 1.100 g/100 ml which is marginally higher than 1.033 g/100 ml produced by K. eutrophaennullThesis