Journal
JOURNAL OF ENVIRONMENTAL MANAGEMENT
Volume 299, Issue -, Pages -Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jenvman.2021.113619
Keywords
Laccase; White rot fungi; Purification; Characterization; Immobilization; Bioremediation
Categories
Funding
- National Natural Science Foundation of China [U2003211, 32070016, 31670016]
- Beijing Forestry University Outstanding Young Talent Cultivation Project [2019JQ03016]
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This study discovered a new pH- and temperature-stable laccase, Galacc-F, from Ganoderma australe, with high activity, broad substrate specificity, and stability in industrial processes. The enzyme was successfully immobilized onto Fe3O4@Chitosan composite nanoparticles using glutaraldehyde as a crosslinker, showing high tolerance to various conditions.
By virtue of screening, purification, and properties characterization, this study captures a new pH- and temperature-stable laccase, designated Galacc-F, from Ganoderma australe for dye bioremediating applications. The enzyme was purified to homogeneity by salt precipitation, ionic exchange, and size exclusion chromatography with a final specific activity of 22.214 U mg(-1), yielding a purification fold of 23.989 and recovery of 38.44%. Its molecular weight was estimated to be 48.0 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, zymography, Sephadex G-100 column, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, which confirmed its monomeric nature. Galacc-F exhibited high levels of activity and stability over wide ranges of pH (5.0-8.0) and temperature (10-60 degrees C), which are highly valuable properties in industrial processes. Broad substrate specificity was observed, wherein a better affinity was found for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) with a low value of K-m (164.137 mu M) and higher k(cat)/K-m ratio (1.663 s(-1) mu M-1). Activity was stimulated by Cu2+ and beta-mercaptoethanol but inhibited by ethylenediaminetetraacetic acid, diethylpyrocarbonate, iodoacetic acid, phenylmethylsulfonyl fluoride, and Hg2+, indicating that Galacc-F is a metalloprotease containing a typical histidine-cysteine-serine catalytic triad. It had high tolerance to surfactants, oxidants, and salts. Additionally, a fabricated protocol for native Galacc-F immobilization onto Fe3O4@Chitosan composite nanoparticles using glutaraldehyde as a crosslinker was developed. Most importantly, the enzyme was determined to be ideal for use in efficient treatment of dye effluents as compared with the laccases requiring redox mediators.
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