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Abstract Laccase is one of the widely used enzymes for biotechnological processes. Immobilization of enzymes is a universally accepted approach to increase their reusability and stability. In this study, laccase enzyme from Trametes versicolor was encapsulated for the first time in a chitosan-nanobiochar matrix. The chitosan-tripolyphosphate gel formation technique was employed to produce homogeneous biocatalyst nanoparticles, with 35% effective binding efficiency and 3.5 Units/g apparent activity under the best configuration. The reusability of the encapsulated laccase was demonstrated towards the oxidation of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) for several consecutive cycles, exhibiting 30% of the initial activity after 5 cycles. The encapsulated laccase showed a moderate increase in enzyme stability against pH and temperature variation compared to the free enzyme. Moreover, the storage stability of laccase at both 4 °C and 25 °C was increased after immobilization. Only 2% of laccase was leaked during a 5-day period from biocatalyst. Laccase in its free form showed no antibacterial activity against Gram positive and Gram-negative model microorganisms, while encapsulated laccase showed antibacterial activity towards Gram-positive ones. Thus, the encapsulation of the laccase is an efficient method to keep the enzyme active and stable for different applications. Highlights • The biocatalyst showed 35% of binding efficiency and 3.5 Units/g apparent activity. • The encapsulated laccase showed higher stability compare to free enzyme. • Encapsulated laccase onto chitosan-nanobiochar exhibited antimicrobial activity. [ABSTRACT FROM AUTHOR]

Immobilization of enzymes on the solid supports can improve the stability as well as catalytic properties of enzymes. In this study, biochar derived from various feedstocks were used as immobilization support considering biochars carbon negative as well as sustainable properties. Partially purified (concentrated) crude laccase was covalently immobilized onto pine wood (BC-PW), pig manure (BC-PM) and almond shell (BC-AS) micro-biochars using optimized 5% w/v glutaraldehyde. Moreover, citric acid pretreatment improved the laccase binding capacity of all the micro-biochars and the highest laccase binding of 40.2 ± 1.8 U g −1 was observed with BC-PM in comparison with raw BC-PM (34.1 ± 1.1 U g −1 ). The enhanced binding of laccase on BC-PM over wood derived biochars was attributed to the higher surface area (46.1 m 2  g −1 ) of BC-PM. Moreover, feedstock selection as well as a method of production influenced the biochar physicochemical properties such as surface area and consequently, different biochars showed various laccase immobilization efficiencies. BC-PW showed better pH, thermal, storage, and operational stability, compared with BC-AS and BC-PM. While applying the laccase bound micro-biochar, complete removal was observed in 2 h under batch mode with 0.5 g of laccase bound BC-PM at an environmentally relevant concentration of 500 µg L −1 in wastewater effluent. About 40% of the laccase activity was retained with all the laccase-bound micro-biochars after 5 cycles of diclofenac treatment. [ABSTRACT FROM AUTHOR]

Although enzymes are gifted with unique and unprecedented catalytic activity and selectivity over a wide range of pollutants, still their stability related issues often hinder their application in real environmental conditions. In this study, agro-industrially produced crude laccase was concentrated using ultrafiltration. Crude laccase was immobilized on pine wood (BC-PW), pig manure (BC-PM) and almond shell (BC-AS) biochar microparticles. Immobilization of laccase was investigated at various laccase activities on micro-biochars and the release (desorption) of the enzyme has been studied. It was observed that for all the biochars, as the initial concentration of laccase increased in the crude solution, the binding capacity and as result immobilization efficiency also increased. BC-PM was found to be the most effective (31.4 ± 3.1 U g −1 ) at 10 U mL −1 of enzyme activity followed by BC-AS (24.3 ± 4.8 U g −1 ) and BC-PW (14.58 ± 3.3 U g −1 ). In addition, the biochars were functionalized with citric acid for possible surface modifications and the effect of biochars for the adsorption of enzymes has been investigated. Isotherm studies of enzyme loading onto biochar established homogeneous monolayer adsorption as the major mechanism. The desorption of laccase from all biochars followed pseudo-second-order model. Immobilized laccase exhibited superior storage ability and shelf-life which were three times higher than free laccase. Finally, the immobilized laccase was used for the degradation of micropollutant, DCF and near 100% removal was obtained within 5 h at an environmentally relevant concentration (500 μg L −1 ). [ABSTRACT FROM AUTHOR]

Biochars were prepared from feedstocks pinewood and pig manure. Biochar microparticles obtained through grinding were evaluated for the removal of emerging contaminant diclofenac (DCF) and the underlying mechanism were thoroughly studied. Characterization of biochar was carried out using particle size analyzer, SEM, BET, FT-IR, XRD, XPS and zeta potential instrument. Pig manure biochar (BC-PM) exhibited excellent removal efficiency (99.6%) over pine wood biochar (BC-PW) at 500 µg L −1 of DCF (environmentally significant concentration). Intraparticle diffusion was found to be the major process facilitated the adsorption. BC-PW followed pseudo first-order kinetics whereas BC-PM followed pseudo second-order kinetics. Pine wood biochar was largely affected by pH variations whereas for pig manure biochar, pH effects were minimal owing to its surface functional groups and DCF hydrophobicity. Thermodynamics, presence of co-existing ions, initial adsorbate concentration and particles size played substantial role in adsorption. Various isotherms models were also studied and results are presented. [ABSTRACT FROM AUTHOR]

Environmental considerations along with the technological challenges have led to search for green and energy-efficient processes for advanced nanostructured materials. In this study, nanobiochar was produced from pine wood biochar using a planetary ball mill. A central composite experimental design and response surface methodology was employed to optimize the ball milling parameters including time, rotational speed and ball to powder mass ratio to obtain nanoparticles in short time and at lower energy consumption. ANOVA results showed that the linear and quadratic effect estimates of time and the interaction effect of time and rotational speed were significant contributors to the size of particles during milling (p < 0.05). Based on the developed statistical model, the optimum conditions for obtaining the smallest particles, around 60 nm, were found to be 1.6 h, 575 rpm and 4.5 g/g. However, the size measurements indicated that particles had a great tendency to agglomerate. Further study showed that the conditioning of biochar at cryogenic temperatures prior to milling inhibits the agglomeration of nanoparticles which is essential in industrial processes. The adsorption test proved that the nanobiochar produced using green method is promising in the removal of micropollutants from aqueous media by removing up to 95% of carbamazepine from water. At the optimum milling parameters and conditioning for 24 h at −80 °C, nanobiochar with the average size of around 60 nm was obtained. The produced nanobiochar was characterized by Brunauer-Emmett-Teller (BET) gas porosimetry, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Also, physical and chemical properties, such as water holding capacity, organic matter, oxidation-reduction potential (ORP), elemental composition, polycyclic aromatic hydrocarbons (PAHs) and heavy metals were analyzed. [ABSTRACT FROM AUTHOR]

Biochar microparticles were prepared from three different types of biochar, derived from waste materials, such as pine wood (BC-PW), pig manure (BC-PM) and cardboard (BC-PD) under various pyrolysis conditions. The microparticles were prepared by dry grinding and sequential sieving through various ASTM sieves. Particle size and specific surface area were analyzed using laser particle size analyzer. The particles were further characterized using scanning electron microscope (SEM). The adsorption capacity of each class of adsorbent was determined by methylene blue adsorption tests in comparison with commercially available activated carbon. Experimental results showed that dye adsorption increased with initial concentration of the adsorbate and biochar dosage. Biochar microparticles prepared from different sources exhibited improvement in adsorption capacity (7.8 ± 0.5 mg g −1 to 25 ± 1.3 mg g −1 ) in comparison with raw biochar and commercially available activated carbon. The adsorption capacity varied with source material and method of production of biochar. The maximum adsorption capacity was 25 mg g −1 for BC-PM microparticles at 25 °C for an adsorbate concentration of 500 mg L −1 in comparison with 48.30 ± 3.6 mg g −1 for activated carbon. The equilibrium adsorption data were best described by Langmuir model for BC-PM and BC-PD and Freundlich model for BC-PW. [ABSTRACT FROM AUTHOR]