(191ah) Extraction, Purification and Modification of Poly (3-hydroxybutyrate) Produced By the Fermentation of Fatty Acids with Burkholderia Cepacia B27

Synthetic polymers are composed by monomeric units that came from fossil hydrocarbons, this materials are widely used around the world due to its low production cost and good mechanical properties. The main application of this materials is packaging, which represents a short useful life in most cases. Usually, many packages are used one, or a couple times before they are discarded, this and the non-biodegradable behavior of most synthetic polymers used for packaging caused the amount of plastics in landfills to grow from 1% in 1960 to 10% in 2005, and the accumulation of millions of tons of plastic waste in water bodies all around the world [1]. That is why in recent years, the interest in the synthesis of materials able to replace the conventional polymers but with high biodegradation rates and low toxicity has grown.

Polyhydroxialkanoates (PHAs) are thermoplastic polyesters synthetized by a large group of bacteria under stress conditions (limitation of nutrients), to store energy as intracellular fat deposit; they are biodegradable and non-toxic, and some of them have interesting mechanical properties that allow them to be used in the packaging industry. Poly (3-hydroxibutyrate) or P3HB is a linear homochiral, and crystalline biopolymer that belongs to a group of short chain PHAs [2]. It’s widely studied due to its mechanical properties that are similar to those of polypropylene [3], but with a better oxygen barrier. It is also resistant to hydrolytic degradation, which is a feature that many other biopolymers like PLA or starch-based polymers lack. However, it’s necessary to improve some of its weakest characteristics like the high brittleness, the production cost and the narrow processing window. This improvements can be achieved using different extraction, purification and modification technics that result in materials with different physicochemical characteristics and production costs [4].

In the Biotechnology institute of the National University of Colombia research works have been developed in the production of the biopolymer Poly (3-hydroxybutyrate) from strains isolated from Colombian soils. This strains were evaluated from a microbiological and operational point of view and the strain Burkholderia cepacia 2G57 was selected and genetically modified to create the P3HB hyperproductive mutant Burkholderia cepacia B27 [5], also, studies to optimize the production process were carried out, evaluating different operational conditions in 7L, 100L and 2000L fermentations [6] and different extraction and purification techniques like the digestion of the biomass with SDS and the purification of the polymer with CHCl3 and NaClO obtaining as result a yellowing material with strong odor and apparent low molecular weight due to its high fragility and poor mechanical properties. In this work different purification processes were evaluated in order to obtain a high purity polymer. Initially, the polymer was extracted and separated from the surrounding PHA hyper-productive mutant bacteria Burkholderia cepacia B27 biomass, using chemical digestion with SDS, centrifugation and solvent precipitation with ethanol. Then the polymer was purified to remove protein and oil residues from the fermentation, for this the performance of different solvents such as ethanol and methanol was tested under different operation conditions. High purity polymer with good mechanical properties, colorless and odorless was obtained. All the samples were thermally characterized (TGA and DSC) to evaluate purity and crystallinity of the resulting materials.

References

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