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Production of Polyhydroxyalkanoates from Thermophilic Bacilli

Divya, M.V. (2008) Production of Polyhydroxyalkanoates from Thermophilic Bacilli. [Student Project Report]

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Abstract

This Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page.

Item Type: Student Project Report
Additional Information: Plastic materials have become an integral part of contemporary life because of many desirable properties including durability and resistance to degradation. PHAs are produced by many bacterial species under nutrient limiting condition with excess carbon. These water insoluble storage polymers are biodegradable exhibit thermoplastic properties. Microorganisms are known to produce PHAs by utilizing some of the industrial byproducts and other cheaper raw materials as carbon sources (molasses, starch, whey, methanol etc). Nearly 88% of P(3HB) /I /h has been obtained by fermentation process and the cost is estimated to be $2.6/kg. With current advances in PHA research, a concentration of more than 80 g/l and productivity of more than 2 g/l/h have been obtained in the laboratory. In the present work, Gram positive thermophilic Bacillus spp. were isolated from different soil samples and screened for PHA production at 37°C and 45°C. The isolated thermophilic Bacillus spp. failed to produce substantial amount of PHA at 45°C and PHA was produced by carrying out fermentation at 37°C. The isolates were identified based on the microscopic observation as well as by performing biochemical tests. On the basis of the data obtained, isolates capable of accumulating PHA were selected for optimization. PHA extraction was carried out by treatment with sodium hypochlorite and chloroform extraction method. Different parameters used for the optimization were temperature, initial pH, rate of inoculum and fermentation period. After obtaining PHA films, characterization was carried out by performing FTIR, GC and NMR analysis. Optimized parameters like 30°C, pH- 7.0 and rate of inoculum- 10% were found to be favourable for the Bacillus sp. isolate no. 18. Similarly, for the isolate no. Xb, 37° C, pH- 6.0 and rate of inoculum- 10% gave remarkable results for an incubation period of 72 h. In case of isolate no. 18, 72 h fermentation period gave the highest biomass i.e., 5.54 g/l, likely 46.48 % was PHA yield. Due to difference 55 in the culture conditions, isolate no. Xb produced little biomass i.e., 2.08 g/l with 26.92% PHA yield. The GC analysis showed the monomer composition of PHA molecules. Here, butyrate was present in the concentration of 95-97 %, whereas, valerate was very less i.e., from 0.62-1.39 %. The FTIR spectrum of the PHA extracted from isolates 18 and Xb, showed the presence of the bends which was compared with the standard and confirmed as PHB. From the NMR data, it was observed that both the isolates showed similar peaks interpreting that the polymer produced is prominently PHB. It was also noted that, there were no peaks attributing the presence of the co-polymer in the PHA produced. Hence, the result describes the presence of PHB in significant amounts. It was concluded that although the isolates were of thermophilic nature, they fail to produce PHA at higher temperatures. However, PHA yield of 46% was noticed with one of the isolates (Bacillus Sp. 18), which is encouraging to take up this strain for further studies to increase the yield of PHA. Use of cheaper carbon and nitrogen substrate may substantially reduce the cost of the PHA, which is essential to commercialize this biodegradable polymer as an alternate to non biodegradable petroleum derived packing materials.
Uncontrolled Keywords: polyhydroxyalkanoates thermophilic Bacillus
Subjects: 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 27 Polymer Chemistry
500 Natural Sciences and Mathematics > 07 Life Sciences > 04 Microbiology
Divisions: Food Microbiology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 04 Jun 2009 09:33
Last Modified: 28 Dec 2011 10:08
URI: http://ir.cftri.com/id/eprint/9001

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