Document Detail

Poly(3-hydroxybutyrate) production from glycerol by Zobellella denitrificans MW1 via high-cell-density fed-batch fermentation and simplified solvent extraction.
MedLine Citation:
PMID:  19666728     Owner:  NLM     Status:  MEDLINE    
Industrial production of biodegradable polyesters such as polyhydroxyalkanoates is hampered by high production costs, among which the costs for substrates and for downstream processing represent the main obstacles. Inexpensive fermentable raw materials such as crude glycerol, an abundant by-product of the biodiesel industry, have emerged to be promising carbon sources for industrial fermentations. In this study, Zobellella denitrificans MW1, a recently isolated bacterium, was used for the production of poly(3-hydroxybutyrate) (PHB) from glycerol as the sole carbon source. Pilot-scale fermentations (42-liter scale) were conducted to scale up the high PHB accumulation capability of this strain. By fed-batch cultivation, at first a relatively high cell density (29.9 +/- 1.3 g/liter) was obtained during only a short fermentation period (24 h). However, the PHB content was relatively low (31.0% +/- 4.2% [wt/wt]). Afterwards, much higher concentrations of PHB (up to 54.3 +/- 7.9 g/liter) and higher cell densities (up to 81.2 +/- 2.5 g/liter) were obtained by further fed-batch optimization in the presence of 20 g/liter NaCl, with optimized feeding of glycerol and ammonia to support both cell growth and polymer accumulation over a period of 50 h. A high specific growth rate (0.422/h) and a short doubling time (1.64 h) were attained. The maximum PHB content obtained was 66.9% +/- 7.6% of cell dry weight, and the maximum polymer productivity and substrate yield coefficient were 1.09 +/- 0.16 g/liter/h and 0.25 +/- 0.04 g PHB/g glycerol, respectively. Furthermore, a simple organic solvent extraction process was employed for PHB recovery during downstream processing: self-flotation of cell debris after extraction of PHB with chloroform allowed a convenient separation of a clear PHB-solvent solution from the cells. Maximum PHB recovery (85.0% +/- 0.10% [wt/wt]) was reached after 72 h of extraction with chloroform at 30 degrees C, with a polymer purity of 98.3% +/- 1.3%.
Mohammad H A Ibrahim; Alexander Steinbüchel
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-08-07
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  75     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2009 Oct 
Date Detail:
Created Date:  2009-09-24     Completed Date:  2009-12-11     Revised Date:  2010-09-27    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  6222-31     Citation Subset:  IM    
Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
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MeSH Terms
Aeromonadaceae / growth & development,  metabolism*
Ammonia / metabolism
Culture Media / chemistry
Glycerol / metabolism*
Hydroxybutyrates / metabolism*
Polyesters / metabolism*
Sodium Chloride / metabolism
Time Factors
Reg. No./Substance:
0/Culture Media; 0/Hydroxybutyrates; 0/Polyesters; 0/Solvents; 26063-00-3/poly-beta-hydroxybutyrate; 56-81-5/Glycerol; 7647-14-5/Sodium Chloride; 7664-41-7/Ammonia

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