DefinePK

Abstract

This study focuses on the production, purification, and biotechnological applications of laccase enzyme synthesized by Aspergillus niger under surface fermentation conditions. Laccases are multi-copper oxidases with wide substrate specificity, enabling their use in diverse industries such as textiles, food processing, and environmental remediation. A locally isolated strain of A. niger was cultivated, and fermentation parameters were systematically optimized using the one-factor-at-a-time (OFAT) approach. Carbon and nitrogen sources, pH, temperature, incubation period, and metal ion supplementation were evaluated to enhance enzyme yield. Sucrose (4 g/100 mL) and yeast extract (5 g/100 mL) were identified as optimal nutritional sources, while pH 6.0, incubation at 30 °C, and a 7-day fermentation period yielded maximum extracellular activity (0.416 ± 0.016 U/mL). Copper (0.5 g/100 mL) acted as a strong inducer, whereas higher concentrations of zinc and iron salts inhibited production. Biochemical characterization revealed maximum activity at 37 °C and pH 5.5, confirming the enzyme’s moderate thermostability and acidic optimum. Partial purification by TLC and ammonium sulfate precipitation enriched enzymatic activity. The crude laccase displayed strong bioremediation potential: textile effluents were decolorized up to 50.78% after 10 days, while tannery wastewater exhibited rapid decolorization of 66.6% within 24 hours. These findings highlight the industrial significance of A. niger laccase as an eco-friendly biocatalyst and establish optimized conditions for its scalable production and application in wastewater treatment.