Incorporation of polyethylene glycol in polyhydroxyalkanoic acids accumulated by Azotobacter chroococcum MAL-201 |
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Authors: | Soma Pal Saha A Patra AK Paul |
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Institution: | (1) Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, 700019 Kolkata, India;(2) Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, 700009 Kolkata, India |
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Abstract: | Azotobacter chroococcum MAL-201 (MTCC 3853), a free-living nitrogen-fixing bacterium accumulates poly(3-hydroxybutyric acid) PHB, 69% of cell dry weight (CDW)] when grown on glucose and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) PHBV with 19.2 mol% 3HV] when grown on glucose and valerate. Use of ethylene glycol (EG) and/or polyethylene glycols (PEGs) of low molecular weight as sole carbon source were detrimental to A. chroococcum growth and polymer yields. PEG-200, however, in the presence of glucose was incorporated into the polyhydroxyalkanoate (PHA) polymer. Addition of PEG-200 (150 mM) to culture medium during mid-log phase growth favored increased incorporation of EG units (12.48 mol%) into the PHB polymer. In two-step culture experiments, where valerate and PEG simultaneously were used in fresh medium, EG was incorporated most effectively in the absence of glucose, leading to the formation of a copolymer containing 18.05 mol% 3HV and 14.78 mol% EG. The physico-mechanical properties of PEG-containing copolymer (PHBV–PEG) were compared with those of the PHB homopolymer and the PHBV copolymer. The PHBV–PEG copolymer appeared to have less crystallinity and greater flexibility than the short-chain-length (SCL) PHA polymers. |
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Keywords: | Polyhydroxyalkanoic acid Poly(3-hydroxybutyric acid) Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Polyethylene glycol PHBV– PEG copolymers |
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