Bioplastics production through mixed microbial cultures eco-engineering

• Autor(a) principal: Pereira, Joana Sofia Marques
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/21085
• topic: Cultura (Biologia) - Microbiologia; Materiais biocompatíveis; Plásticos biodegradáveis; Reciclagem de resíduos - Indústria agro-alimentar; Biopolímeros

Bioplastics have been the focus of interest as a sustainable alternative to conventional plastics. Among those, polyhydroxyalkanoates (PHA) can be highlighted, not only for their biocompatibility and biodegradability, but also because they can be produced by mixed microbial cultures (MMC) from agro-industrial wastes. This allows to substantially reduce the production costs and valorize alternative substrates. PHA have a wide range of characteristics according to their composition, which allows them to be used in many applications. The polymers characteristics can be manipulated through the control of several operational parameters during the production process. Production of PHA by MMC in this work was based in a three-stage process: acidification of a by-product of the paper industry, hardwood spent sulphite liquor (HSSL), selection of a PHA accumulating microbial culture and PHA production. The selection step occurred in a sequencing batch reactor (SBR), operated for 180 days, and whose conditions were changed in order to select for a PHA-accumulating culture and with good PHA volumetric production. Three pseudo-stationary states (PSS) were achieved after successive increases in the selective pressure, a clear indication that the MMC was able to adapt to the substrate and to the imposed conditions. In the last step of this work several accumulation assays were performed that allowed for the validation of the use of HSSL acidified under different conditions and Condensate (another byproduct of the paper industry) for PHA production. The best test performed achieved a maximum accumulation of 74.7% cdw and a volumetric productivity of 0.27 gPHA/L.h. This work allowed to show the potential of the use of PHA producing MMC as a way of valorization of agroindustrial byproducts and residues.