Optimization of Culture Conditions for Enhanced Laccase Expression by Marine Acinetobacter sp. M6

AbstractLaccases are versatile multicopper oxidases capable of oxidizing a broad range of phenolic and non-phenolic compounds, making them valuable for applications such as bioremediation, textile dye removal, pulp bleaching, and biosensor design. While fungal laccases are extensively studied, bacterial laccases—particularly those from marine environments—offer advantages in terms of stability under extreme conditions. In this study, we investigated laccase production by a marine Acinetobacter sp. M6 using three different growth media: Luria–Bertani (LB) broth, Nutrient Broth (NB), and Brain Heart Infusion (BHI). Enzyme activity was monitored at various incubation times using ABTS and guaiacol as substrates. LB medium supported the highest laccase output, with peak activity occurring between 72 and 84 hours. Supplementing LB with copper sulfate enhanced enzyme production, with 0.2 mM identified as the optimal concentration. ABTS was more sensitive than guaiacol for detecting enzyme activity. These findings indicate that LB medium supplemented with copper sulfate provides favorable conditions for efficient laccase production by marine Acinetobacter sp. M6, highlighting its potential for industrial and environmental applications. Keywords Laccase; Marine Acinetobacter sp.; Media optimization; ABTS assay; Copper induction