Glycerol is a co-product of many industrial processes and is generated in large quantities from different origins. In this study, glycerol is used as a cheap carbon source for the production of poly(3-hydroxybutyrate) (PHB) with two different collection strains, Cupriavidus necator and Burkholderia sacchari, in order to provide an alternative outlet for glycerol and produce value-added bioproducts. The objective of this work was to study the influence of this carbon source on their growth kinetics, on their polymer production, and on the molecular mass of the produced biopolymer. Therefore, fermentations in bioreactors were carried out with these strains. Different results for both strains were obtained showing, for the first time, a high cell dry mass and growth rate, when glycerol was used together with glucose in the fermentation with C. necator. In the first fermentation with B. sacchari using glycerol as a sole carbon source, the strain properly developed synthesising PHB. The biopolymers obtained from both fermentations with glycerol showed low molecular masses about 300 kDa with a polydispersity of 4.72 with C. necator, and 200 kDa with polydispersity of 2.50 with B. sacchari.
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 1Á64 h À1 . 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.
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-2yl)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-2yl)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%).
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