Production of medium-chain-length polyhydroxyalkanoates by Pseudomonas aeruginosa with fatty acids and alternative carbon sources.

In this study, medium-chain-length polyhydroxyalkanoates (mcl-PHAs) were produced by Pseudomonas aeruginosa using different carbon sources. Decanoic acid induced the highest (9.71% [+/- 0.7]) mcl-PHAs accumulation in bacterial cells at 47 h. The cells preferred to accumulate and degrade the polyhydroxyoctanoate than polyhydroxydecanoate (PHD) during early stage and final stage of the growth, respectively. The production cost of mcl-PHAs can be reduced by using edible oils as the carbon source. The bacteria accumulated 6% (+/- 0.7) of mcl-PHAs in the presence of olive oil. Besides, reused oil was another potential carbon source for the reduction of the production cost of mcl-PHAs. Overall, PHD was the major constituent in the accumulated mcl-PHAs.

Construction of recombinant Bacillus subtilis for production of polyhydroxyalkanoates.

Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates synthesized by numerous bacteria as intracellular carbon and energy storage compounds and accumulated as granules in the cytoplasm of cells. In this work, we constructed two recombinant plasmids, pBE2C1 and pBE2C1AB, containing one or two PHA synthse genes, respectively. The two plasmids were inserted into Bacillus subtilis DB104 to generate modified strains, B. subtilis/pBE2C1 and B. subtilis/pBE2C1AB. The two recombinants strains were subjected to fermentation and showed PHA accumulation, the first reported example of mcl-PHA production in B. subtilis. Gas Chromatography analysis identified the compound produced by B. subtilis/pBE2C1 to be a hydroxydecanoate-co-hydroxydodecanoate (HD-co-HDD) polymer whereas that produced by B. subtilis/pBE2C1AB was a hydroxybutyrate-co-hydroxydecanoate-co-hydroxydodecanoate (HB-HD-HDD) polymer.

Construction of recombinant Escherichia coli strains for production of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate).

Plastic wastes constitute a worldwide environmental problem, and the demand for biodegradable plastics has become high. One of the most important characteristics of microbial polyesters is that they are thermoplastic with environmentally degradable properties. In this study, pUC19/PHA was cloned and transformed into three different Escherichia coli strains. Among the three strains that were successfully expressed in the production of polyhydroxyalkanoates (PHA), E. coli HMS174 had the highest yield in the production of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (P[HB-HV]). The cell dry weight and PHA content of recombinant HMS174 reached as high as 10.27 g/L and 43% (w/w), respectively, in fed-batch fermentor culture. The copolymer of PHA, P(HB-HV), was found in the cells, and the biopolymers accumulated were identified and analyzed by gas chromatography, proton nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. We demonstrated clearly that the E. coli host for PHA production has to be carefully selected to obtain a high yield. The results obtained indicated that a superior E. coli with high PHA production can be constructed with a desirable ratio of P(HB-HV), which has potential applications in industry and medicine.

[Polyhydroxyalkanoates microbiological synthesis from food wastes].

To reduce the production cost of polyhydroxyalkanoates (PHAs), the process feasibility and physicochemical properties of PHAs synthesized by Alcaligenes latus, Staphylococcus epidermidis and activated sludge from malt waste, soy waste, confectionary waste, ice cream waste, milk waste, sesame oil and vinegar waste were analyzed. Results showed that through two-stage fed-batch fermentation, the maximum yield of PHAs accumulated by the three kinds of microorganisms from malt waste was 70.1%, 16.0% and 43.3%, separately. A. latus adapted itself to the food wastes in PHAs synthesis and new cell growth quickly. A. latus had higher PHAs yield and productivity under nitrogen limited condition. Micro-aerobically, S. epidermidis separated from sesame oil could produce polyhydroxybutyrate (PHB) with molecular weight of over 1 x 10(6). From soy waste, activated sludge accumulated polyhydroxybutyrate-co-hydroxyvaluate (PHBV) copolymer which had hydroxyvaleryl content (HV%) of 21%. Most food wastes are suitable for synthesizing PHAs with different physicochemical properties. The composition and properties of PHAs are influenced by the character of microorganism, the selection of substrates and optimization of ferment conditions.