Solid-State Fermentation as a Sustainable Tool for Extracting Phenolic Compounds from Cascalote Pods

Cascalote pods are an important source of phenolic compounds, mainly recovered using solvent extraction methods. To find a sustainable alternative to these methods, this study aimed to evaluate solid-state fermentation (SSF) in order to enhance the extractability of total phenolic compounds (TPC) with antioxidant activity (AA) from cascalote pods. Aspergillus niger GH1 was selected based on the amount of TPC released and AA measured (ABTS, DPPH, FRAP) in a short period of time. Moreover, moisture, temperature, inoculum size, and mineral composition were evaluated. The largest amount of TPC released was 124.17 mg/gdw (g of dry weight) after 12 h of culture, which significantly correlated with the AA (Pearson’s R = 0.94). Moisture and KH2PO4 concentration were the main influencing factors of TPC release. Treatment 6 (1 × 107 spores/gdw, 30 °C, 60% moisture, mineral composition (g/L): KH2PO4, 1.52; NaNO3, 7.65; and MgSO4, 1.52) was selected due to the highest values of both TPC and AA. SSF-assisted extraction allowed for an increase of 118% and 93% in TPC and AA values, respectively. Corilagin, lagerstannin, geraniin, and ellagic acid were the main phenolic compounds identified by RP-HPLC-ESI-MS in the cascalote extracts. The results obtained demonstrate the feasibility of SSF-assisted extraction as a biotechnological alternative for the recovery of important bioactive molecules from this underutilized material.