Optimization of enhanced collagen extraction from tannery rawhide trimming waste using pineapple peel-derived bromelain enzyme through response surface methodology

Plant-based enzymatic extraction of collagen from tannery rawhide trimmings can play an important role in the utilization tannery solid waste, providing economically viable and sustainable solutions. This study employed bromelain enzyme derived from pineapple (Ananas comosus) peel waste for collagen extraction and compared the procedure with conventional acetic acid extraction. The recovery of bromelain enzyme at 30–70% ethanol precipitation exhibited a 2.21-fold purification and a 98% yield. Response surface methodology (RSM) analysis revealed that bromelain enzyme-extracted collagen (BEC) yielded 82.20% at a hydrolysis time of 18.39 h, a mixing ratio of 22.38, and a temperature of 39.32 °C. In contrast, a lower yield of 66.94% was observed in the case of acetic acid-extracted collagen (AEC) at a hydrolysis time of 18.66 h, a mixing ratio of 19.41, and a temperature of 27.09 °C. Fourier transform infrared spectroscopy (FTIR) confirmed the successful extraction of both AEC and BEC. Thermogravimetric analysis (TGA) indicated the higher thermal stability of BEC compared to AEC. X-ray Diffraction (XRD) displayed characteristic peaks of collagen in the range of 2θ of 15–25°, affirming that BEC (sharp peak at 19.49°) is more crystalline than AEC (broadening peak at 19.88°). Elemental analysis revealed a higher nitrogen content (6.78%) in BEC, indicating a higher protein content than that of AEC (6.31%). Furthermore, antimicrobial activity, cytotoxicity evaluation, and heavy metal analysis revealed the potential applications of collagen in cosmetics, biomaterials, and tissue engineering.