Immobilization of laccase from Bacillus subtilis DS on chitosan beads and standardization of process for biodegradation of textile dyes

BACKGROUND The textile industry generates a huge amount of effluents containing different hazardous dyes. Indigo carmine and malachite green are the most commonly used dyes in textile and dye industries. Pollution caused by these dyes affects aquatic life. RESULTS Bacillus subtilis DS produces an alkali-thermostable laccase. This enzyme was immobilized on chitosan beads and conditions for immobilization were optimized. After immobilization, the maximum activity of 26 IU g(-1) beads was found under optimized conditions of 1% glutaraldehyde, 3 h cross-linking time and 5 h immobilization time. The immobilized enzyme retained a temperature and pH profile similar to that of the free enzyme. Significant enzyme activity was retained after ten reaction cycles with >60% stability after 15 days, allowed reuse of enzyme over multiple cycles. Immobilized laccase was used to degrade textile dyes and the conditions were standardized statistically for its optimal degradation. Under optimized conditions a high degradation rate was achieved for indigo carmine (95.24%) and malachite green (90%), respectively. CONCLUSION Immobilized laccase is a highly suitable candidate for bioremediation of textile industry dyes because of its stability and reusability. (c) 2021 Society of Chemical Industry