Enhanced antioxidant capacity and yield of release of chlorogenic acids and derivates by solid-state fermentation of spent coffee ground under controlled conditions of aeration and moisturizing

This study proposed investigates the role of forced aeration flow and humidification pulses during solid-state fermentation (SSF) of spent coffee grounds (SCG) in optimizing fungal growth, metabolic activity, and bioactive compound release. Five fermentation conditions with aeration flows (0.5–1.5 L/min) and moisturizing pulses (30–90 mL/d) were evaluated. Chlorogenic acid (CGA), caffeic acid (CA), and quinic acid (QA) were quantified via HPLC, while antioxidant activities (AA) were assessed using ORAC, DPPH, and FRAP methods. The highest CGA yield (76.1 ± 5.2 mg/g SCG_initial) occurred between days 8–13 under 0.5LA-30LM conditions, while QA peaked at 89.5 ± 4.8 mg/g SCG_initial during days 27–30 under 0.5LA-90HM. AA reached 79,000 μmol TEAC/100 g SCG_initial at late fermentation stages. Low aeration and controlled moisture enhanced fungal colonization, enzymatic hydrolysis, and bioactive compound recovery. These findings evidence the potential of SSF for SCG valorization and offer a framework for process optimization in industrial applications.