Enzymatic potential of filamentous fungi for pretreatment of spent coffee grounds for acidogenic fermentations

• Autor(a) principal: Cachinho, Ana Sofia Aguiar
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/31131
• topic: Spent coffee grounds; Enzyme production; Trametes versicolor; Paecilomyces variotii; Acidogenic fermentation; Short-chain organic acids

With resource depletion and increasing waste production, lignocellulosic biomass has been studied as biorefinery substrates. Due to its characteristics, spent coffee grounds (SCG) can be applied in numerous bioprocesses, such as the production of short-chain organic acids (SCOA). SCOA are versatile and high valued metabolites that can be produced by Acidogenic Fermentation (AF) as an alternative to the petrochemical process. To enhance AF competitiveness is necessary to improve the hydrolysis rate which can be achieved by enzymatic or chemical hydrolysis. Enzymatic hydrolysis is considered a more sustainable alternative. However, enzymes are costly, and consequently, chemical hydrolysis is the preferred option. Since the used substrate represents a huge cost in enzyme production, new strategies are necessary. One possibility is the use of organic wastes. These cheap substrates can contribute to reducing production costs. In this work, the sole effect of SCG (0.4 and 1.0% w/v) and the combined effect of SCG and pineapple peel (PP) (0.4 + 0.2% w/v and 1.0 + 0.4% w/v) were studied as inducers for enzyme production by Trametes versicolor and Paecilomyces variotii. In the assay with 0.4% SCG, a laccase activity in T. versicolor of 350 U/L was recorded. Posteriorly, the enzymatic extracts obtained were used for SCG pretreatment. To select the best pretreatment for SCOA production, AF was performed with SCG submitted to different physicochemical and biological pretreatments. Generally, the main SCOA produced were acetic, and propionic acids. Acid hydrolysis led to the highest SCOA concentration (2.52 g COD/L) but submerged fermentation by T. versicolor led to a similar SCOA concentration (2.44 g COD/L) and higher acidification degree (48.0%). The obtained results showed the great potential of T. versicolor enzymes for SCG pretreatment. The experiments performed allowed us to conclude that SCG can be potentially used as a laccase inducer and as a substrate for SCOA production, however, these processes must be optimized to become more competitive.