Screening of exopolysaccharides (EPS) and polyhydroxyalkanoates (PHA) from sediments from the Azores Archipelago, Canay Islands and Estremadura Spur

• Autor(a) principal: Batista, Maria Rita Nicolau
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/138713
• topic: exopolysaccharides; polyhydroxyalkanoates; bacteria; marine; screening; carbon sources; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

Oceans are still largely unexplored as a source of new and interesting biomolecules. Among these, exopolysaccharides (EPS) and polyhydroxyalkanoates (PHA) are being widely studied for their interesting biotechnological applications in various industrial fields. EPS are produced by bacteria as a defense mechanism against biotic or abiotic stress, like low temperatures or high salinity. PHA are also produced as a survival mechanism, but against carbon shortage, they accumulate as intracellular granules, in order to be used as energy source in the absence of some nutrients. In this work, bacteria were isolated from sediments from the Azores Archipelago, Canary Islands and Estremadura Spur and screened for the production of EPS and PHA. Growth assays were performed in glucose, glycerol, fructose, xylose and lactose, as well as 16°C and 30°C, two different nitrogen concentrations were also tested. The majority of the cultures grew better at 30°C, but produced more EPS at 16°C. All cultures presented fluorescence under the light microscope, meaning they all produce PHA. Different cultures showed different preferences of carbon source, and also the bacteria that produced more biomass, were not the one that produced more EPS. Three of the cultures with the most interesting results were cultivated in a bioreactor, at standard operating conditions. From all of the bacteria, C3 showed the most balanced results of EPS and PHA production, reaching biomass concentration of 2.013 g/L, a specific growth rate of 0.370 h-1 and volumetric productivities of 78.89 mgEPS/L.h-1 and 40.83 mgPHA/L.h-1. Az4 was taxonomically identified a Bacillus sp., and presented similar growth results to culture C3, but with lower biopolymer production. Az7 produced the highest biomass, but both productions of polymer were low, also to notice that this culture produced a bright orange pigment, which we could not yet identify.