Agri-food waste valorization through Monascus ruber fermentation for natural pigment production: bioconversion efficiency, neuroprotective potential, and functional food relevance

Six agri-food side streams, linseed press cake (LPC), brewer's spent grains (BSG), bread residues (BR), apple pomace (AP), sugar beet pulp (SBP), and acid cheese whey (CW), were compared as feedstocks for compound-resolved Monascus ruber SRZ112-m22 pigment production under submerged (SmF) and liquid-surface fermentation (LSF). Authentic-standard HPLC quantified five azaphilones across days 3-8. Apple-pomace hydrolysate gave the highest measured total titer in SmF (1042.85 mg/L, day 7), whereas bread-residue hydrolysate was optimal in LSF (504.65 mg/L, day 6), demonstrating strong substrate-by-cultivation-mode control of pigment yield and profile. Purified monascin, monascorubrin, and rubropunctamine bound AChE, BChE, MAO-A, and PPAR-gamma, but binding was not interpreted as therapeutic efficacy. Post-cultivation liquid caused only slight bakery coloration at 40% replacement and inconsistent antioxidant changes, identifying concentration, process, and safety constraints. This within-strain comparison links compound-specific fermentation kinetics to preliminary molecular and food-matrix screening while supporting waste valorization consistent with the United Nations Sustainable Development Goals SDG 12.3.