Bioproduction of Poly-3-Hydroxybutyrate and Study for a Specific Genetic Application

Abstract

The serious ambient problems from the wide plastic use had made the scientific community suggest the substitution of conventional plastics for biodegradable ones. Polyhydroxyalcanoats (PHAs) are biopolyesters produced from natural and renewable sources and due to its properties are a viable alternative to common based-mineral-oil plastics. Unfortunately, poly-3-hydroxybutyrate P(3HB) still face some economical problems owing its high production costs, where subtract prices and fermentation temperatures maintenance (cooling expenses) are important factors. On the other hand, PHAs has recently attracted a great deal of interest as carrier for drug delivery or scaffolds in tissue engineering given its easy processability, excellent biocompatibility, and propensity to biodegradating under different environmental conditions. Being that given, the current work has as main target the study for high production of P(3HB), using a novel bacterium capable of utilize an economic, renewable and abundant carbon source (as sucrose) for the synthesis of this biopolymer. Also the adaptation of this strain to high temperature, in order to decrease the cooling costs, is an important goal in this study. As a secondary goal, is intended to manufacture shell-core capsules using the extracted P(3HB). These capsules should be able to isolate and carrier oligonucleotides (OLNs) needed for a genetic diagnosis application. Among the described PHA producing bacteria, Burholderia sacchari is known to be able to metabolize sucrose towards P(3HB). However, no detailed data are available yet for the capacity of the strain for PHA production and for the quality of the products. Therefore, a broad range of experiments were carried out in this thesis with this strain- adaptation to higher temperatures, different media compositions and the cultivation under controlled conditions in a bioreactor. The results show that the bacterium was successfully adapted to higher temperatures. Also, in this conditions and in the bioreactor fermentation the strain was able to reach a cell dry mass (CDM) of 70 g/L with P(3HB) content of about 53%, which is considerably high. Concerning the secondary goal of this thesis, some modified encapsulation techniques where tested. Even though solid capsules with sizes between 100 nm and 10 μm were obtained, its oligonucletide encapsulation yield needs improvements. Work regarding this issue is still undergoing.