Document Detail


Polyhydroxyalkanoate copolymers from forest biomass.
MedLine Citation:
PMID:  16761168     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The potential for the use of woody biomass in poly-beta-hydroxyalkanoate (PHA) biosynthesis is reviewed. Based on previously cited work indicating incorporation of xylose or levulinic acid (LA) into PHAs by several bacterial strains, we have initiated a study for exploring bioconversion of forest resources to technically relevant copolymers. Initially, PHA was synthesized in shake-flask cultures of Burkholderia cepacia grown on 2.2% (w/v) xylose, periodically amended with varying concentrations of levulinic acid [0.07-0.67% (w/v)]. Yields of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) [P(3HB-co-3HV)] from 1.3 to 4.2 g/l were obtained and could be modulated to contain from 1.0 to 61 mol% 3-hydroxyvalerate (3HV), as determined by 1H and 13C NMR analyses. No evidence for either the 3HB or 4HV monomers was found. Characterization of these P(3HB-co-3HV) samples, which ranged in molecular mass (viscometric, Mv) from 511-919 kDa, by differential scanning calorimetry and thermogravimetric analyses (TGA) provided data which were in agreement for previously reported P(3HB-co-3HV) copolymers. For these samples, it was noted that melting temperature (Tm) and glass transition temperature (Tg) decreased as a function of 3HVcontent, with Tm demonstrating a pseudoeutectic profile as a function of mol% 3HV content. In order to extend these findings to the use of hemicellulosic process streams as an inexpensive carbon source, a detoxification procedure involving sequential overliming and activated charcoal treatments was developed. Two such detoxified process hydrolysates (NREL CF: aspen and CESF: maple) were each fermented with appropriate LA supplementation. For the NREL CF hydrolysate-based cultures amended with 0.25-0.5% LA, P(3HB-co-3HV) yields, PHA contents (PHA as percent of dry biomass), and mol% 3HV compositions of 2.0 g/l, 40% (w/w), and 16-52 mol% were obtained, respectively. Similarly, the CESF hydrolysate-based shake-flask cultures yielded 1.6 g/l PHA, 39% (w/w) PHA contents, and 4-67 mol% 3HV compositions. These data are comparable to copolymer yields and cellular contents reported for hexose plus levulinic acid-based shake-flask cultures, as reported using Alcaligenes eutrophus and Pseudomonas putida. However, our findings presage a conceivable alternative, forestry-based biorefinery approach for the production of value-added biodegradable PHA polymers. Specifically, this review describes the current and potential utilization of lignocellulosic process streams as platform precursors to PHA polymers including hemicellulosic hydrolysates, residual cellulose-derived levulinic acid, tall oil fatty acids (Kraft pulping residual), and lignin-derived aromatics.
Authors:
Thomas M Keenan; James P Nakas; Stuart W Tanenbaum
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Publication Detail:
Type:  Journal Article; Review     Date:  2006-04-27
Journal Detail:
Title:  Journal of industrial microbiology & biotechnology     Volume:  33     ISSN:  1367-5435     ISO Abbreviation:  J. Ind. Microbiol. Biotechnol.     Publication Date:  2006 Jul 
Date Detail:
Created Date:  2006-06-08     Completed Date:  2007-01-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9705544     Medline TA:  J Ind Microbiol Biotechnol     Country:  England    
Other Details:
Languages:  eng     Pagination:  616-26     Citation Subset:  IM    
Affiliation:
Department of Environmental and Forest Biology, State University of New York, College of Environmental Science and Forestry (SUNY-ESF), Syracuse, NY 13210, USA.
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MeSH Terms
Descriptor/Qualifier:
Alcaligenes / growth & development,  metabolism
Biotechnology*
Burkholderia cepacia / growth & development,  metabolism*
Industrial Microbiology / methods*
Polyesters / chemistry,  metabolism*
Pseudomonas putida / growth & development,  metabolism
Wood / metabolism,  microbiology*
Chemical
Reg. No./Substance:
0/Polyesters; 0/poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate)

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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