ISOLATION, SCREENING AND SELECTION OF EFFICIENT POLY-p-HYDROXYBUTYRATE (PHB) SYNTHESIZING BACTERIA
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Date
2007-08-30
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University of Agricultural Sciences GKVK, Banglore
Abstract
In 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. eutropha
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