Valorization of Pineapple Peel Waste through Immobilized Crude Bromelain for Enhanced Feed Protein Hydrolysis

Pineapple processing generates considerable waste with byproducts (peels, cores, crowns, and leaves) often containing high levels of bromelain, a proteolytic enzyme with promising applications in animal feed. However, the instability and low activity of crude bromelain (CBr) in aqueous form limit its industrial utilization. In this study, CBr was extracted from pineapple peel waste and directly immobilized onto a bentonite (Bt)-carboxymethylcellulose (CMC) composite without further purification. The CBr-Bt-CMC composites were prepared via ionotropic gelation, with cysteine incorporated to enhance enzymatic performance. The composite with a bromelain-to-cysteine mass ratio of 1:65 could enhance catalytic activity by over 1,000% compared to the control without cysteine. It exhibited an immobilization yield exceeding 80% with significantly improved thermal stability, retaining nearly twice the activity of free CBr after 10 min at 100 °C. Application of the immobilized CBr in soybean meal (SBM) hydrolysis demonstrated significant improvements in nutritional value (approximately 3-fold), degradation of allergenic proteins, and generation of low-molecular-weight peptides at 60-70 °C within 30 min. Immobilized CBr exhibited sustained catalytic performance, retaining over 60% of its initial activity after four cycles. Collectively, these results highlight the potential of the immobilized crude bromelain as a robust and efficient biocatalyst for the enhancement of nutritional value in feed protein.