Fungal Biodegradation of Procyanidin in Submerged Fermentation

The coffee industry generates a large amount of waste that is difficult to treat due to its chemical composition, namely, the presence of caffeine and its derivatives, as well as recalcitrant molecules such as tannins (mainly condensed tannins or polymeric procyanidins), which make it an undervalued waste product. Procyanidins are compounds beneficial to human health and can be found in nature in fruit, grain, seeds, and beverages, among other foods. The zero-waste approach has allowed for the valorization of by-products from the food industry. Currently, coffee pulp is the target of research on extraction, purification, and alternative use. Research on the fungal degradation of procyanidins has emerged as an avenue for the efficient use of these by-products. In this study, the degradation and biotransformation of procyanidin is evaluated and comprises three steps: first, the extraction and partial purification of procyanidins from coffee pulp; second, the production of the potential procyanidin-degrading enzyme by submerged fermentation with Aspergillus niger GH1; third, enzymatic extracellular extract evaluation using a model system with commercial procyanidin C1. The biodegradation/biotransformation results reveal the formation of new compounds, including a final compound with an m/z of 289, possibly a monomeric molecule such as catechin or epicatechin. Identification of the compounds by HPLC-MS confirmed procyanidin C1 depletion under the described assay conditions, which could be used to understand biodegradation pathways proposed for future study. Furthermore, these results confirm that A. niger GH1 is able to degrade and biotransform procyanidin C1.