Organic acids production from industrial wastes by microbial mixed cultures

• Autor(a) principal: Oliveira, André Carvalho de
• 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/10773/36690
• topic: Short-chain organic acids; Acidogenic fermentation; Waste valorization; Potato chips spent frying oil; Crude glycerol

The utilization of fossil-fuel based plastics is a serious environmental problem. Biobased plastics derived from biopolymers emerged as a sustainable and eco-friendly alternative. Polyhydroxyalkanoates (PHAs) are promising candidates due to their biodegradability and similar properties to synthetic plastics. Mixed microbial cultures (MMC) are promising candidates to reduce the PHAs production costs since they do not require sterilization and adapt to a broad range of carbon sources. When using MMC, the most common method for PHAs production is the three-step process, that includes a first step of acidogenic fermentation to obtain short chain organic acids (SCOAs), the selection of a PHAs-producing population under feast and famine regime, and finally the accumulation of PHAs. There are few studies on the use of crude glycerol (CG) and none related to the use of spent frying oil (SFO) to produce SCOAs, via acidogenic fermentation. In this work, it was possible to assess the effectiveness of MMC of the inocula chosen to produce SCOAs from SFO and CG. SFO is mainly composed of lipids, being oleic acid the major fatty acid present in its composition (ca. 81%). For acidogenic fermentation of SFO, the 1:2 food/microorganisms (F/M) ratio allowed to obtain the best results, with aerobic sludge (AES) inoculum resulting in 78.40% of acidification degree (AD), with a diverse production of SCOAs. For acidogenic fermentation of CG, the 1:1 F/M ratio allowed to obtain the best results, with the sludge from biodiesel production (BPS) leading to an AD of 68.69%. This work can be considered a starting point of acidogenic fermentation studies with lipid-based substrates, standing as an interesting strategy to reduce industrial waste, to reduce pollution and to turn PHAs production into a more economic, sustainable, and eco-friendly solution, following the circular economy concept.