High production of poly(3-hydroxybutyrate) from a wild Bacillus megaterium Bolivian strain.

AIM: Taking into account that a novel strain of Bacillus megaterium was isolated from Uyuni salt lake (Bolivia) in a previous work, the objectives of this new study were to determine the maximal Poly-3-hydroxybutyrate production potential of B. megaterium strain uyuni S29 in an industrial conventional media, the possibility that the strain accumulates different types of polyhydroxyalkanoates, the cellular morphology during the biosynthesis process and the characterization of the produced biopolymers. METHODS AND RESULTS: The micro-organism was first tested in a 3-L bioreactor obtaining a high specific growth rate of 1·64 h(-1). A second fed-batch experiment was carried out in shaking flasks, reaching up to 70% PHB of cell dry mass. The biosynthesized polymers were extracted by two different extraction procedures and characterized. The results showed that all of them were PHB with thermal properties different to the conventional PHB. The micrographs taken by TEM show the different cell morphology during the fermentation process. CONCLUSIONS: In this previous study, the strain not only grew properly in the industrial conditions proposed without spore formation, but also produced and accumulated a large content of PHB, never reached before for its genus. Therefore, if the culture conditions can be optimized, the biopolymer production could be increased. SIGNIFICANCE AND IMPACT OF THE STUDY: The impact of the study has related to the area of the biomaterials and their production. The study provides new data related to the high production of PHB from the wild novel strain B. megaterium uyuni S29, the highest polymer accumulation for the genus Bacillus without spores formation.

The Concept of Docking/Protecting Groups in Biohydroxylation.

A general principle for biohydroxylation, in which time-consuming screening and enrichment techniques are avoided, is demonstrated by the introduction of a docking/protecting group into the substrate. This facilitates acceptance by the microorganism and allows the use of a narrow range of microorganisms, for example Beauveria bassiana ATTC 7159 (B. b.), for the hydroxylation of compounds with diverse structures. After the biohydroxylation, the docking/protecting group is removed (see scheme).

Polyhydroxyalkanoates, biopolyesters from renewable resources: physiological and engineering aspects.

Polyhdroxyalkanoates (PHAs), stored as bacterial reserve materials for carbon and energy, are biodegradable substitutes to fossil fuel plastics that can be produced from renewable raw materials. PHAs can be produced under controlled conditions by biotechnological processes. By varying the producing strains, substrates and cosubstrates, a number of polyesters can be synthesized which differ in monomer composition. By this means, PHAs with tailored interesting physical features can be produced. All of them are completely degradable to carbon dioxide and water through natural microbiological mineralization. Consequently, neither their production nor their use or degradation have a negative ecological impact. After a historical review, possibilities for the synthesis of novel PHAs applying different micro-organisms are discussed, and pathways of PHA synthesis and degradation are shown in detail for important PHA producers. This is followed by a discussion of the physiological role of the accumulation product in different micro-organisms. Detection, analysis, and extraction methods of PHAs from microbial biomass are shown, in addition to methods for polyester characterization. Strategies for PHA production under discontinuous and continuous regimes are discussed in detail in addition to the use of different cheap carbon sources from the point of view of different PHA producing strains. An outlook on PHA production by transgenic plants closes the review.

Effects of Low Dissolved-Oxygen Concentrations on Poly-(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Production by Alcaligenes eutrophus.

The bacterial copolyester poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) was produced with Alcaligenes eutrophus DSM 545 from glucose and sodium propionate in a fed-batch fermentation with both nitrogen limitation and low dissolved-oxygen concentrations. When the dissolved-oxygen content was kept between 1 and 4% of air saturation during the polymer accumulation phase, the yield of 3-hydroxybutyrate (3HB) monomer from glucose was not affected, but the propionate-to-3-hydroxyvalerate (3HV) monomer yield was two to three times (0.48 to 0.73 mol of 3HV mol of propionate consumed(sup-1)) that observed in a control experiment (0.25 mol mol(sup-1)), where the accumulation-phase dissolved-oxygen concentration was 50 to 70% of air saturation. The overall polymer productivity of the fermentation was somewhat decreased by low dissolved-oxygen contents, owing to a slower 3HB production rate. The effect of a low dissolved-oxygen concentration is probably attributable to a reduction of the oxygen-requiring decarbonylation of propionyl-coenzyme A (CoA) to acetyl-CoA.

Stereospecific Biohydroxylations of Protected Carboxylic Acids with Cunninghamella blakesleeana.

Cunninghamella blakesleeana DSM 1906 was found to be an efficient biocatalyst for the biotransformation of cycloalkylcarboxylic acids into hydroxy and oxo derivatives. When cultivated in submerged culture, the fungus grew in pellets. In comparison with malt extract-glucose-peptone-yeast extract medium (medium E), Czapek-Dox medium was found to reduce pellet size. Cycloalkylcarboxylic acids were protected against microbial degradation by chemical transformation into 2-cycloalkyl-1,3-benzoxazoles. The transformations of protected cyclopentyl-, cyclohexyl-, cycloheptyl-, and cyclooctylcarboxylic acids by C. blakesleeana were investigated. The biotransformations were performed in medium E by using an aerated, stirred-tank bioreactor. The transformation of 2-cyclopentyl-1,3-benzoxazole yielded (1S,3S)-3-(benz-1,3-oxazol-2-yl)cyclopentan-1-ol as the main product. The main by-product was (1R)-3-(benz-1,3-oxazol-2-yl)cyclopentan-1-one, and 2-(benz-1,3-oxazol-2-yl)cyclopentan-1-ol was also obtained in small amounts. During the experiment, the enantiomeric excess of the main product increased up to 64%. 2-Cyclohexyl-1,3-benzoxazole was hydroxylated to 4-(benz-1,3-oxazol-2-yl)cyclohexan-1-ol. 2-Cycloheptyl-1,3-benzoxazole and 2-cyclooctyl-1,3-benzoxazole were transformed into several alcohols and ketones, all in low yields (2 to 19%).