Incorporation of polyethylene glycol in polyhydroxyalkanoic acids accumulated by Azotobacter chroococcum MAL-201.
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.
Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, 700019 Kolkata, India.
Soma Pal
SP
Saha
A
A
Patra
A K
AK
Paul
D001395:Azotobacter / Q000378:metabolism*; D019855:Ethylene Glycol / Q000378:metabolism; D005285:Fermentation; D006880:Hydroxy Acids / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000378:metabolism*; D013997:Time Factors
D006880:Hydroxy Acids; D011092:Polyethylene Glycols; D019855:Ethylene Glycol