Partial Purification of Laccase from Pantoea sp. Strain SMDG01 and Its Efficiency in Synthetic Dyes Decolorization
摘要
Synthetic dyes pose serious environmental and health hazards due to their extensive industrial use. Thus, research groups have primarily focused on fungal laccases for dye decolorization, whereas studies on bacterial laccases remain limited. In this study, a laccase-producing bacterium was successfully isolated and identified as Pantoea sp. strain SMDG01 based on 16S rRNA gene sequence analysis. The isolated bacterium showed highest laccase activity (7.33 U/mL). Partial purification of laccase using Sephadex G-100 chromatography achieved approximately 7.6-fold purification. The SDS-PAGE results suggested that the partially purified laccase exhibited a molecular weight ~ 46 kDa. The optimal activity of partially purified laccase was found to be at pH 5.0, temperature 55 °C, and substrate concentration at 1 mM ABTS. The partially purified laccase effectively decolorized 76.82% of Malachite Green (200 mg/L), 30.25% of Congo Red (200 mg/L) and 21.42% of Azure B (200 mg/L). FTIR analysis confirmed structural changes in malachite green dye after laccase treatment, as evidenced by altered absorption peaks at 3680.72 cm−1, 3480.28 cm−1, 2368.78 cm−1, 1648.08 cm−1(C = C stretching), 1602.33 cm−1 and 781.61 cm−1. Similarly, Congo red and Azure B dyes treated with laccase exhibited a distinctly different peak pattern compared with the untreated samples. Phytotoxicity tests on Vigna radiata seeds showed significant toxicity reduction in decolorized dyes samples, as in malachite green with seed germination of 90% and seedling vigor of 351 indicating detoxification. Our findings indicate that the partial purified laccase (Pantoea sp. strain SMDG01) is an effective biological mediator for the environmental-friendly treatment of dye-contaminated wastewater. Future studies need to be focused on genomic analysis for the improvement of current study.