Microbial Biotechnology

Electronic Journal of Biotechnology ISSN: 0717-3458 Vol. 11 No. 3, Issue of July 15, 2008
© 2008 by Pontificia Universidad Católica de Valparaíso -- Chile Received April 4, 2007 / Accepted December 6, 2007
DOI: 10.2225/vol11-issue3-fulltext-2
RESEARCH ARTICLE

Nutrient optimization for production of polyhydroxybutyrate from halotolerant photosynthetic bacteria cultivated under aerobic-dark condition

Kanokphorn Sangkharak
Department of Industrial Biotechnology
Faculty of Agro-Industry
Prince of Songkla University
Hatyai, Thailand P.O. Box 90112
Tel: 66 7428 6363
Fax: 66 7421 2889
E-mail: skanokphorn@yahoo.com

Poonsuk Prasertsan*
Department of Industrial Biotechnology
Faculty of Agro-Industry
Prince of Songkla University
Hatyai, Thailand P.O. Box 90112
Tel: 66 7428 6369
Fax: 66 7421 2889
E-mail: poonsuk918@yahoo.com

*Corresponding author

Financial support: This work was supported by Thailand Research Fund (TRF) under Royal Golden Jubilee (RGJ)-Ph.D Program.

Keywords: aerobic-dark cultivation, optimization, PHB, polyhydroxybutyrate, Rhodobacter sphaeroides.

Abbreviations:

DCW: dry cell weight
GC-MS: gas chromatography-mass spectrometry
GM: glutamate-malate
NTG: N-methly-N'-nitro-N-nitrosoguanidine
PHAs: polyhydroxyalkanoates
PHB: polyhydroxybutyrate
TEM: transmission electron microscopy
UV: ultraviolet
Abstract   Full Text

Three halotolerant bacterial strains; Rhodobacter sphaeroides ES16 (the wild type) and the two mutant strains of R. sphaeroides ES16, namely N20 and U7, were cultivated in glutamate-malate (GM) medium and screened for production of polyhydroxybutyrate (PHB). The mutant strains N20 and U7 were found to accumulate PHB (53.9 and 42.0% of DCW, respectively) 3.6 and 2.8 times higher than the wild type strain (19.5% of DCW), respectively. R. sphaeroides N20 were selected for studies on the effects of nutrient and environmental conditions on PHB accumulation. The optimal condition was 4 g/l acetate, 0.02 g/l (NH4)2SO4, C/N ratio of 6:1, 1.0 g/l K2HPO4, 1.0 g/l KH2PO4 and 3% NaCl with initial pH at 7.0. Under this optimal condition, the maximum PHB accumulation increased from 53.9% to 88% of DCW and 9.11 ± 0.08 g/l biomass, 8.02 ± 0.10 g/l PHB concentration were achieved after 60 hrs cultivation at 37ºC. These results are the highest values ever obtained from photosynthetic bacteria reported so far.

Supported by UNESCO / MIRCEN network