| Congresso Brasileiro de Microbiologia 2023 | Resumo: 823-1 | ||||
Resumo:Coffee is a drink consumed throughout several continents and cultures. The global production is about 165 million bags of 60 kg to meet the high demand. In coffee production, there are two main processing methods: the wet and dry methods, the latter being the most used in Brazil. The dry method has, as the main by-product, the coffee husk (CH), while the subsequent roast produces a by-product known as coffee silverskin (CSS). Although not intrinsically polluting, the sheer amount of produced by-products turns them into environmental liabilities. To turn the coffee production chain eco-friendlier, the destination of such residues must change. Although nutritious, CH contains several components limiting their use as feedstock food, such as caffeine and tannins. Fungi produce demethylases, which convert caffeine into xanthine, thus making the caffeine's nitrogen available for further use. Several bioprocesses can be used with fungi, such as solid-state cultivation (SSC) and submerged cultivation (SmC). That said, the CH is known to contain high cellulose rates and very little available carbon. To make the existent carbon easier to metabolize, extrusion was chosen as a pretreatment. Extruders disrupt the biomass by breaking the cellulose chain without chemical changes, thus without producing fermentation inhibitors. Therefore, it was selected to use SSC with filamentous fungi as a way to achieve a reduction in caffeine and tannins concentration. Six different Aspergillus strains, two Penicillium strains, and a Trichoderma harzianum strain were selected and subjected to caffeine resistance assay to identify the ones more likely able to degrade said caffeine. From that assay, seven fungi were selected for a caffeine degradation experiment. Despite the lack of nitrogen sources besides caffeine, all the strains could grow in the media. The SSC was conducted with in natura CH, pretreated CH (30-60 rpm, 40°C, 40-80 Nm and 2:1-4:1 CH:water ratio), CSS, and a mix of two or three. In this project, we analyzed the caffeine concentration, using high-performance liquid chromatography (HPLC), the activity of hydrolases of interest, and nutrient characteristics before and after cultivation. Although previous work from the group showed that one of the A. awamori strains was able to degrade caffeine from cocoa by-products, the same strain has been, so far, unable to degrade the caffeine from CH. The attempts with different pretreatment conditions, two concentrations of molasses supplementation, and different mixes of in natura CH, pretreated CH, and CSS had no significant impact on the caffeine degradation. The caffeine degradation by fungi is usually associated with fungi's growth and the demand for nitrogen needed for this. To better comprehend the dynamics of caffeine degradation, N-acetylglucosamine assays were conducted. They showed that the use of extrusion had a negative impact on the fungi growth, reducing fungi growth by 22,5%-36,1%, and that neither the supplementation with molasses nor the change of temperature was enough to level the fungi growth with the untreated husk. Although none of the tried extrusion conditions showed improvement in the fungi growth, further attempts will be carried out with new conditions to verify if extrusion is inefficient in improving fungi growth in CH. Supplementation with other sources of carbon and nitrogen will be tried as well. Palavras-chave: by-products, Caffeine, Coffea arabica, Detoxification, enzyme Agência de fomento:Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPQ | |||||