Ultrasound-accelerated enzymatic hydrolysis of solid leather waste

The leather industry is a heavy pollution industry and looking for clean technology. The utilization of enzyme and ultrasound in the industry are potential eco-friendly technologies. Enzymes can degrade the untanned solid leather waste. According to our investigation, ultrasound (40 kHz, 0.64 W/cm2) has little effect on the activity of one alkaline protease from Bacillus licheniformis. It is the first time to use ultrasound to accelerate the enzymatic hydrolysis of the untanned solid leather waste. With the application of ultrasound, the value of kA for the enzymatic hydrolysis of the untanned solid leather waste increases 18% and KM is almost unchanged, compared with that obtained without ultrasound. Ultrasound improves the ultimate conversion ratio from 57.6% to 84.1%. The reason is that ultrasound can facilitate the protease through the pores of skin and impair the integrity of collagen. Amino acid analysis indicated that ultrasound can promote the breakdown of helical regions of collagen which are difficult to attack by proteases. In view of environment protection, the use of enzyme and ultrasound in combination is a promising clean technology for the disposal of the untanned solid leather waste.