Fermentation of spent coffee grounds by Bacillus clausii induces release of potentially bioactive peptides

Abstract

Spent coffee grounds (SCG) are residues generated during coffee beverage preparation that contain 12–17% protein and are a rich source of peptides. Bacteria can generate peptides with potential bioactivity through protein hydrolysis in a fermentation process. This study aimed to obtain digested protein hydrolysates with potential bioactivity from Bacillus clausii-fermented SCG. The fermentation was performed with 1.5 × 108 colony-forming units/mL of bacteria at 37 °C for 39 h. Total and soluble proteins and protein hydrolysates were quantified using spectrophotometric techniques. Pepsin/pancreatin protein hydrolysates were characterized using ultra-performance liquid chromatography-mass spectrometry. The physicochemical properties and potential bioactivity of peptides were evaluated using in silico analysis. The fermentation process increased the amounts of total proteins, soluble proteins, and protein hydrolysates by 2.7, 2.2, and 1.2-fold, respectively, compared to non-fermented SCG. Fermented SCG samples, increased the abundance of seven peptides that displayed potentially antioxidant capacity, angiotensin-converting enzyme activity, and dipeptidyl peptidase-IV-inhibitor activity. The YGF and GMCC peptide sequences presented the highest bioactivity scores (0.97 each), followed by the YWRYDCQ (0.65) and RMYRY (0.60) peptides. In summary, fermented SCG had increased abundance of peptides with high bioactive potential that may be exploited in managing oxidative stress, hypertension, and diabetes.