Optimization of protein recovery from bovine lung by pH shift process using response surface methodology

BACKGROUND: Response surface methodology (RSM) was used in a sequential manner to optimize solubilization and precipitation conditions in the recovery of protein from bovine lung using pH shift. RESULTS: Separate D-optimal designs were employed for protein solubilization and precipitation. Independent variables investigated for protein solubilization were time (10–120 min), temperature (4–20 °C), pH (8.0–11.0) and solvent/sample ratio (2.5–10). Variables for protein precipitation were time (0–60 min) and pH (4.25–6.00). Soluble protein yields ranged from 323 to 649 g kg⁻¹ and the quadratic model for protein solubilization revealed a coefficient of determination R² of 0.9958. Optimal conditions for maximum protein solubility were extraction time 140 min, temperature 19 °C, pH 10.8 and solvent/sample ratio 13.02. Protein precipitation yields varied from 407 to 667 g kg⁻¹, giving a coefficient of determination R² of 0.9335. Optimal conditions for maximum protein precipitation were pH 5.03 and 60 min. Based on the RSM model, solubilization conditions were manipulated to maximize protein solubilization under reduced water and alkaline usage. These conditions were also validated. CONCLUSION: Models for solubilization and precipitation using bovine and porcine lung were validated; predicted and actual yields were in good agreement, showing cross-species applicability of the results.