Although leather industry plays a significant role in the global economy, it has been categorized as one of highly polluting industries due to its generation of huge amount liquid and solid wastes. Large amount of solid and liquid wastes is generated from tanning industries during leather manufacturing process. These wastes bring about various problems to the environment and human health. Tannery wastes contain significant amount of raw skin wastes that are produced in hide/leather trimming process. The recycling and use of these raw skin/hide wastes (trimming wastes) is very important from environmental as well as economic point of views. The aim of this work was to investigate production of collagen from sheep skin trimming waste. The trimming waste was first pre-treated and then acetic acid hydrolysed to extract collagen. The extracted collagen was characterized using Fourier Transform Infrared (FTIR), UV-spectrometer and Scanning Electron Microscope (SEM). Response Surface Methodology (RSM) was used to optimize collagen extraction parameters (acetic acid, mixing ratio and extraction time). A three-factor, three-level Box-Behnken Design (BBD) based RSM was applied to determine the optimal conditions to obtain maximum collagen yield. A maximum collagen yield of 25.75% was obtained at optimum conditions (acetic acid concentration of 0.54 M, skin to acetic acid ratio of 0.03 g/ml and extraction time 3.33 day) using the RSM. Under these optimum conditions, experimental determined collagen yield of acid-soluble collagen was 25.85% which is in good agreement with the predicted value.

Milk clotting enzymes are one of the most significant cheese making raw materials impacting and regulating milk coagulation activity. Calf rennet is one of the enzymes which extracted from suckling calf abomasum. The rennet extracted was optimized for its clotting time t (s) by varying three levels of temperature (30, 35 and 40 o C), pH (4, 5 and 6) and CaCl 2 concentration (0.1, 0.2 and 0.3 gm/500 ml of milk) using response surface method (RSM) and also its milk clotting activity (MCA) was determined. Based on the optimized result, temperature 39.13 o C, pH 4 and CaCl 2 concentration of 0.21 gm/500ml had resulted minimum clotting time of 91.27 s. Using this minimum clotting time, the strength was found to be 1: 13148, establishing the fact that the calf rennet is the best natural coagulant of milk.