Isolation and characterization of PHAs-accumulating bacteria from HSSL

• Autor(a) principal: Ferreira, Ana Lúcia Morgado
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/13401
• topic: Biotecnologia ambiental; Biopolímeros; Reactores biológicos; Compostos alifáticos

Polyhydroxyalkanoates (PHAs) are biodegradable and biocompatible biopolymers. PHAs emerge as a possible solution as substitutes of petroleum based plastics, being produced under the Biorefinery concept, in which wastes and by-products of numerous industries may be used as carbon source. This project aimed the isolation and characterization of organisms able to store PHAs from Hardwood Sulphite Spent Liquor (HSSL), a by-product of the pulp and paper industry. Isolation was performed from a Mixed Microbial Culture (MMC) selected under feast and famine conditions, using some components present in HSSL as substrates, such as acetic acid and xylose. Five pure isolates able to produce PHAs resulted from the successive streaking in solid medium containing HSSL. The purity of the isolates was evaluated through Gram staining and FISH analysis and the PHAs accumulation by Nile Blue staining. Two strains were identified as Rhohococcus spp. and three as Pseudomonas spp.. One isolate of each genus was selected and further studied in terms of growth and PHAs accumulation capability from three distinct carbon sources (HSSL, acetic acid and xylose). Both isolates, Rhodococcus spp. and Pseudomonas spp., were able to grow and use the three carbon sources as well as to produce PHAs. However, both strains showed a higher maximum specific growth rate (μmax) when HSSL was used as carbon source, 0.212 ± 0.0219 h-1 and 0.251 ± 0.0526 h-1, respectively. A qualitative evaluation of the PHAs accumulation through Nile Blue staining exhibited a higher accumulation when acetic acid was used as sole carbon source. In an attempt to identify some of the species responsible for PHAs accumulation of the selected MMC, belonging to the dominant class, Alphaproteobacteria, a 16S rDNA clone library was constructed. It was possible to identity Novosphingobium spp., Sphingobium spp. and Pleomorphomonas spp.