Production of antibiotics and biopolymer by the bacterium Pseudomonas chlororaphis using glycerol

• Autor(a) principal: Serafim, Bruno Filipe Rodrigues
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/101312
• topic: Pseudomonas chlororaphis; co-production; Phenazines; Medium-chain-length polyhydroxyalkanoates; Exopolysaccharides; Bioreactors; Biotecnologia

Members of the Pseudomonas genus are known for their ability to produce multiple secondary metabolites, including bioactive metabolites, such as antibiotics. Pseudomonas chlororaphis subsp. aurantiaca DSM 19603 is a non-pathogenic bacterium widely used as plant growth-promoting rhizobacteria that has been reported to be able to produce three products of interest, namely, antibiotics (phenazines) and two biopolymers, medium-chain-length polyhydroxyalkanoates (mcl-PHA) and exopolysaccharides (EPS). Phenazines are heterocyclic nitrogenous compounds that can act as antibiotic, antiparasitic or even anticancer agents. PHAs are a class of biobased and biodegradable polymers that depending on their composition and specific properties shows potential application on areas from thermoplastics to elastomers. EPS are a group of natural polymers mainly composed by sugars that due to their variety of physical and structural properties have many applications in industries such as food, pharmaceutical and cosmetics. This biopolymer could also be a good ally in bioremediation. The main objective of this study was to develop and optimize the bioprocess for phenazines and biopolymers (mcl-PHA and EPS) co-production by Pseudomonas chlororaphis using glycerol as carbon source. Different nutrient (nitrogen and carbon) concentrations, pH control with NH4OH and other conditions were tested in order to obtain higher productivities of all mentioned products. The study showed that the same fermentation conditions (standard nutrients concentration and pH control with NH4OH) enabled to achieve the best product concentrations, namely, a significant amount of phenazines (6.05 OD365nm), an EPS concentration of 3.8 g/L and a mcl-PHA concentration of 8.43 g/L. According to literature, this mcl-PHA concentration is the highest achieved in P. chlororaphis fermentations. Further, carbon and nitrogen concentrations in culture medium seems to impact the mcl-PHA composition, which could guarantee different properties to this polymer.