Limits...
Ionic polymer-coated laccase with high activity and enhanced stability: application in the decolourisation of water containing AO7.

Zhang X, Hua M, Lv L, Pan B - Sci Rep (2015)

Bottom Line: The stability of the resulting LacPG was highly enhanced against pH variations, thermal treatments and provided better long-term storage with a negligible loss in enzymatic activity.Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7.The increased size and modified surface chemistry of LacPG facilitated ultrafiltration and reduced membrane fouling.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, P.R. China.

ABSTRACT
Eliminating dyes in environmental water purification remains a formidable challenge. Laccase is a unique, environmentally friendly and efficient biocatalyst that can degrade pollutants. However, the use of laccase for the degradation of pollutants is considerably limited by its susceptibility to environmental changes and its poor reusability. We fabricated a novel biocatalyst (LacPG) by coating polyethylenimine onto the native laccase (Lac) followed by crosslinking with glutaraldehyde. The stability of the resulting LacPG was highly enhanced against pH variations, thermal treatments and provided better long-term storage with a negligible loss in enzymatic activity. Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7. LacPG was separated from the AO7 solution using an ultrafiltration unit. The increased size and modified surface chemistry of LacPG facilitated ultrafiltration and reduced membrane fouling. LacPG exhibited enhanced stability, high catalytic activity and favourable properties for membrane separation; therefore, LacPG could be continuously reused in an enzymatic membrane reactor with a high efficiency for decolourising water containing AO7. The developed strategy appears to be promising for enhancing the applicability of laccase in practical water treatment.

Show MeSH

Related in: MedlinePlus

Cyclic Lac or LacPG-mediated decolourisation of AO7 solution: (a) decolourisation efficiency for active or deactivated biocatalysts (deactivated at 60°C for at least 24 h) and residual enzymatic activity and (b) fresh AO7 solution (100 mg·L−1) and effluents from the 10th cyclic run.Biodegradation of 100 mg·L−1 AO7 phosphate buffer solution (pH 5.0, 0.05 M) containing 0.1 mM HBT and LacPG or native laccase (0.1 mg laccase protein per mL, ca. 0.8 U·mL−1) at 25°C; LacPG or Lac were recycled for continuous runs; ultrafiltration: pressure = 0.1 MPa, 25°C; error bars show standard deviations for triplicate measurements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4317704&req=5

f7: Cyclic Lac or LacPG-mediated decolourisation of AO7 solution: (a) decolourisation efficiency for active or deactivated biocatalysts (deactivated at 60°C for at least 24 h) and residual enzymatic activity and (b) fresh AO7 solution (100 mg·L−1) and effluents from the 10th cyclic run.Biodegradation of 100 mg·L−1 AO7 phosphate buffer solution (pH 5.0, 0.05 M) containing 0.1 mM HBT and LacPG or native laccase (0.1 mg laccase protein per mL, ca. 0.8 U·mL−1) at 25°C; LacPG or Lac were recycled for continuous runs; ultrafiltration: pressure = 0.1 MPa, 25°C; error bars show standard deviations for triplicate measurements.

Mentions: The cyclic decolourisation results for Lac and LacPG are shown in Fig. 7. Heat deactivation (60°C for at least 24 h) was used to estimate the effects of AO7 absorption by Lac or LacPG in the enzymatic membrane reactor under otherwise identical conditions. The deactivated LacPG and Lac removed ca. 25% and 7% of AO7 by adsorption in the first run, respectively, whereas the decolourisation efficiency sharply decreased to ca. 0% within three cyclic runs. When using either Lac or LacPG, the decolourisation efficiency was as high as ca. 94% during the first cyclic run. After ten cyclic runs, the decolourisation efficiency of Lac dramatically decreased to ca. 39%, and the corresponding laccase activity decreased to ≃1% (≃8.5 U·L−1). In contrast, after ten cyclic runs, the activity of LacPG remained at >80% of its initial activity. Thus, LacPG consistently maintained its decolourisation efficiency (ca. 94%) in the enzymatic membrane reactor even after ten cyclic runs.


Ionic polymer-coated laccase with high activity and enhanced stability: application in the decolourisation of water containing AO7.

Zhang X, Hua M, Lv L, Pan B - Sci Rep (2015)

Cyclic Lac or LacPG-mediated decolourisation of AO7 solution: (a) decolourisation efficiency for active or deactivated biocatalysts (deactivated at 60°C for at least 24 h) and residual enzymatic activity and (b) fresh AO7 solution (100 mg·L−1) and effluents from the 10th cyclic run.Biodegradation of 100 mg·L−1 AO7 phosphate buffer solution (pH 5.0, 0.05 M) containing 0.1 mM HBT and LacPG or native laccase (0.1 mg laccase protein per mL, ca. 0.8 U·mL−1) at 25°C; LacPG or Lac were recycled for continuous runs; ultrafiltration: pressure = 0.1 MPa, 25°C; error bars show standard deviations for triplicate measurements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4317704&req=5

f7: Cyclic Lac or LacPG-mediated decolourisation of AO7 solution: (a) decolourisation efficiency for active or deactivated biocatalysts (deactivated at 60°C for at least 24 h) and residual enzymatic activity and (b) fresh AO7 solution (100 mg·L−1) and effluents from the 10th cyclic run.Biodegradation of 100 mg·L−1 AO7 phosphate buffer solution (pH 5.0, 0.05 M) containing 0.1 mM HBT and LacPG or native laccase (0.1 mg laccase protein per mL, ca. 0.8 U·mL−1) at 25°C; LacPG or Lac were recycled for continuous runs; ultrafiltration: pressure = 0.1 MPa, 25°C; error bars show standard deviations for triplicate measurements.
Mentions: The cyclic decolourisation results for Lac and LacPG are shown in Fig. 7. Heat deactivation (60°C for at least 24 h) was used to estimate the effects of AO7 absorption by Lac or LacPG in the enzymatic membrane reactor under otherwise identical conditions. The deactivated LacPG and Lac removed ca. 25% and 7% of AO7 by adsorption in the first run, respectively, whereas the decolourisation efficiency sharply decreased to ca. 0% within three cyclic runs. When using either Lac or LacPG, the decolourisation efficiency was as high as ca. 94% during the first cyclic run. After ten cyclic runs, the decolourisation efficiency of Lac dramatically decreased to ca. 39%, and the corresponding laccase activity decreased to ≃1% (≃8.5 U·L−1). In contrast, after ten cyclic runs, the activity of LacPG remained at >80% of its initial activity. Thus, LacPG consistently maintained its decolourisation efficiency (ca. 94%) in the enzymatic membrane reactor even after ten cyclic runs.

Bottom Line: The stability of the resulting LacPG was highly enhanced against pH variations, thermal treatments and provided better long-term storage with a negligible loss in enzymatic activity.Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7.The increased size and modified surface chemistry of LacPG facilitated ultrafiltration and reduced membrane fouling.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, P.R. China.

ABSTRACT
Eliminating dyes in environmental water purification remains a formidable challenge. Laccase is a unique, environmentally friendly and efficient biocatalyst that can degrade pollutants. However, the use of laccase for the degradation of pollutants is considerably limited by its susceptibility to environmental changes and its poor reusability. We fabricated a novel biocatalyst (LacPG) by coating polyethylenimine onto the native laccase (Lac) followed by crosslinking with glutaraldehyde. The stability of the resulting LacPG was highly enhanced against pH variations, thermal treatments and provided better long-term storage with a negligible loss in enzymatic activity. Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7. LacPG was separated from the AO7 solution using an ultrafiltration unit. The increased size and modified surface chemistry of LacPG facilitated ultrafiltration and reduced membrane fouling. LacPG exhibited enhanced stability, high catalytic activity and favourable properties for membrane separation; therefore, LacPG could be continuously reused in an enzymatic membrane reactor with a high efficiency for decolourising water containing AO7. The developed strategy appears to be promising for enhancing the applicability of laccase in practical water treatment.

Show MeSH
Related in: MedlinePlus