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Characterization of Bacterial Polyhydroxyalkanoates from Agro-Industrial Residues

Esaivani, E. (2010) Characterization of Bacterial Polyhydroxyalkanoates from Agro-Industrial Residues. [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: The aim of the present work is to characterize the PHA produced by Bacillus sp. using agro-industry residues such as Groundnut oil cake, Til oil cake and Rice bran as their supplement. They are supplemented as fatty acid source to increase the quality of the PHA produced and to find out whether they give rise to co-polymers. The work was first started with supplementing the PHA production medium with different oil cakes. Five different oil cakes were first used. They include- GOC, TOC, COC, SOC and CSOC. Throughout the study, the concentration of oil cake was maintained at 2% level and that of Rice bran was 0.5% level. Among the five, GOC and TOC along with RB were found to be the best. Hence, these two oil cakes were taken for further analysis and the experiment was tried with both crude oil cakes and their hydrolysates. It was found that GOC with RB Unhydrolysed (Sample no.6) and TOC with RB (Hydrolysed) were best. And the PHA produced by these oil cakes at different combinations was subjected to direct chloroform extraction and these samples were taken for characterization. For characterization, Crotonic acid assay, UV-Spectrophotometry for determination of λ-max, FT-IR, Gas chromatography and NMR spectroscopy were performed. Finally, molecular weight was determined for one PHA sample no.10 from Production medium produced by Bacillus sp. λ-max determination revealed that the polymers obtained were PHA. By crotonic acid assay, concentration of the samples was determined and it showed that Sample no. 6 and Sample no.10 were pure when compared to other samples. However, PHA obtained from production medium was more pure than sample no.6 and 10. FT-IR analysis showed that the spectrum for sample no.7, 9 and 11 indicated as PHB molecules. In sample no.6, the band at 2931 cm-1 indicates that it may be a scl-co-mcl PHA. In sample no.10, transmittance band at 1730.4 cm-1 indicates that it may be a copolymer. GC analysis showed that many of the polymers obtained were Polyhydroxybutyrate. All the samples showed retention time around 6th minute. None of the samples showed retention time around 11th minute. But sample no. 6 and 10 showed a peak with retention time around 28th min and it is due to mcl-PHA molecule. PHA films formed after sodium hypochlorite extraction showed good quality film with more flexibility. Hence, it can be concluded that the sample no. 6 and 10 were co-polymers of PHB and mcl-PHA molecule and sample no. 7, 9 and 11 were PHB molecules.In sample no. 6, the area (%) of PHB is 66.1 and that of the mcl-PHA molecule is 1.1. The ratio of co-polymer PHB : mcl PHA is 98 : 2. Similarly, in sample no.10, the area (%) of PHB is 60.5 and that of mcl-PHA molecule is 2.7. The ratio of co-polymer PHB : mcl PHA is 95 : 5. 1H NMR studies showed that, sample no.6 contains PHB and mcl- PHAs. The peaks between 4 – 4.5 ppm indicates the presence of mcl-PHA. The peak at 0.53 indicates that the sample contains trace amount of valerate (HV). Sample no.10 also shows the presence of mcl-PHA. Hence, we conclude that the sample no. 6 is a copolymer of PHB and mcl-PHA along with trace amount of PHV and sample no.10 is a copolymer of PHB and mcl-PHA Molecular weight was determined for sample no.10 produced by Bacillus sp. in PHA production medium. Molecular weight was determined using Oswald viscometer by calculating intrinsic viscosity. The molecular weight of the sample was found to be 3.96 x105 Da. Mineral oil prices will rise substantially in the next century, forcing the world to consider alternatives for petrochemical plastics. PHAs are gaining serious consideration as substitute for non-biodegradable petrochemical plastics. Currently their production is expensive, but these plastics are only in their first stage of commercial development (Lee, 1996). Further research on recombinant microbial strains, mixed cultures, efficient fermentation, recovery, purification and the use of inexpensive substrates like agro-industry residues can substantially reduce the production cost.
Uncontrolled Keywords: PHA; Bacillus sp.; oil cakes; polyhydroxyalkanoates
Subjects: 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 27 Polymer Chemistry
Divisions: Food Microbiology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 08 Jul 2010 11:42
Last Modified: 28 Dec 2011 10:15
URI: http://ir.cftri.com/id/eprint/9482

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