Preparation and synthetic dye decolorization ability of magnetic cross-linked enzyme aggregates of laccase from Bacillus
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RESEARCH PAPER
Preparation and synthetic dye decolorization ability of magnetic cross‑linked enzyme aggregates of laccase from Bacillus amyloliquefaciens Hongrao Wang1,2 · Shuran Han2 · Jiayi Wang2 · Shuyu Yu3 · Xiaoyan Li1,2 · Lei Lu1,2 Received: 30 September 2020 / Accepted: 9 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Laccases are versatile oxidases that are capable of decolorizing various synthetic dyes. Recombinant Bacillus amyloliquefaciens laccase was immobilized as magnetic cross-linked enzyme aggregates (M-CLEAs) for application in dye decolorization. Several parameters influencing the activity recovery were evaluated during the synthesis of M-CLEAs. With ammonium sulfate as precipitant, maximum activity was recovered by cross-linking with 0.16% glutaraldehyde for 1 h. The prepared M-CLEAs exhibited improved activity under alkaline conditions. It remained 74% activity after incubation at 60 °C for 5 h. Enhanced tolerance towards NaCl was also observed for the M-CLEAs, with 68% activity remaining in the presence of 1 M NaCl. The immobilized laccase could rapidly decolorize more than 93% of reactive black 5 and indigo carmine in 1 h, while its catalytic efficiency towards reactive blue 19 was relatively low. After four cycles of consecutive reuse, the M-CLEAs could decolorize 92% of indigo carmine. The easy recovery and reusability of M-CLEAs facilitate the potential application of bacterial laccase in dye decolorization. Keywords Cross-linked enzyme aggregates · Laccase · Immobilization · Dye · Decolorization
Introduction Synthetic dyes are extensively used in many industries, including textile, paper printing, pharmaceutical, food and cosmetic industries. The textile industry is the largest consumer of synthetic dyes, and about 5–50% of the dyes are lost in the effluents during the dyeing process [1, 2]. Textile wastewater is usually featured by its high BOD, COD, color, salinity and temperature, which make it very difficult to treat [1]. Besides, most synthetic dyes from textile industries are toxic or mutagenic and can stably remain in the environment for an extended period of time. Therefore, it is very * Lei Lu [email protected] 1
Key Laboratory of Saline-Alkali Vegetation Ecology Restoration (Northeast Forestry University), Ministry of Education, Harbin 150040, China
2
Present Address: College of Life Sciences, Northeast Forestry University, No. 26, Hexing Road, Harbin 150040, China
3
College of Water Conservancy and Civil Engineering, Inner Mongolia Agricultural University, Hohhot 010018, China
important to find a suitable method to treat dye effluents for protecting human and ecological health [2]. Several physicochemical methods have been developed for dye removal from industrial wastewater, such as reverse osmosis, membrane-filtration and flocculation [1]. However, few of them have been widely used in the textile industries due to their high cost, low efficiency and secondary pollution problems [1, 2]. Biological treatment is generally co
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