Lignocellulosic fibres surface interactions in enzymatic reaction using data-mining

Lignocellulosic fibres modification focused so far essentially on the resulting material properties to create functional fibres instead of determining the reaction influencing parameters. Using a data-mining algorithm, surface chemical composition of the fibres after modifications was compared to multiple signals. A 24 h reaction at either 25 °C or 60 °C, pH5 was conducted in presence of trans-ferulic acid, laccase, and lignocellulosic fibres (flax, hemp, or cellulose) having different chemical surface composition. Dimers and trimers were detected in variable concentrations in the reaction filtrate and extractive. At 25 °C, crystalline cellulose, amorphous cellulose, xylans, mannans, and lignins were well correlated to specific reaction products while at 60 °C, only lignins and xylan were found correlated to reaction products. Fibres surface composition affected the extractive profile. Lignocellulosic surface composition influence on the product formed was unveiled using a data mining approach. This study presents a way to unveil non-evident chemical interface interaction in reactions.

A novel approach to efficient degradation of indole using co-immobilized horseradish peroxidase-syringaldehyde as biocatalyst

Biocatalytic degradation technology has received a great deal of attention in water treatment because of its advantages of high efficiency, environmental friendliness, and no secondary pollution. Herein, for the first time, horseradish peroxidase and mediator syringaldehyde were co-immobilized into functionalized calcium alginate composite beads grafted with glycidyl methacrylate and dopamine. The resultant biocatalyst of the co-immobilized horseradish peroxidase-syringaldehyde system has displayed excellent catalytic performance to degrade indole in water. The degradation rate of 100% was achieved in the presence of hydrogen peroxide even if the indole concentration was changing from 25 mg/L to 500 mg/L. If only the free enzyme was used under the identical water treatment conditions, the degradation of indole could hardly be observed even when the concentration of indole is low at 25 mg/L. This was attributed to the effective co-immobilization of the enzyme and the mediator so that the catalytic activity of horseradish peroxidase and the synergistic catalytic action of syringaldehyde could be fully developed. Furthermore, while the spherical catalyst was operated in succession and reused for four cycles in 50 mg/L indole solution, the degradation rate remained 91.8% due to its considerable reusability. This research demonstrated and provided a novel biocatalytic approach to degrade indole in water by the co-immobilized horseradish peroxidase-syringaldehyde system as biocatalyst.

Mold resistance of bamboo after laccase-catalyzed attachment of thymol and proposed mechanism of attachment

Laccase-catalyzed attachment of functional molecules onto the surface of bamboo represents an alternative, green approach to improve performance. Although treatment of bamboo with thymol improved resistance to mold, using laccase to fix the same concentration of thymol to the surface of the bamboo could increase both the antifungal activity and resistance to leaching. Leaching of thymol was reduced by as much as 48.4% when laccase was used in thymol fixation. To make clear the mechanisms of fixation, reaction of thymol catalyzed with laccase, was investigated using Fourier-transform infrared spectroscopy, ¹H-NMR, high-resolution mass spectrometry and thermogravimetric analysis, respectively. Results show that thymol oligomer (l-thymol) was formed with ether linkages, which resist water leaching. Although further confirmatory studies are needed, it seems that ether linkages were the main connection of thymol to lignin. This study demonstrates that laccase catalysis is a promising strategy to functionalize the surface of bamboo in order to bestow new properties suitable for a wide range of applications.

Schematic diagram of laccase-catalysed fixation of natural antimicrobial phenol to bamboo.

Effect of Laccase-Mediated Biopolymer Grafting on Kraft Pulp Fibers for Enhancing Paper's Mechanical Properties

High-resistance paper was manufactured by laccase-grafting of carboxymethyl cellulose (CMC) and chitosan (CPX) on Kraft pulp fiber. The reaction was mediated in the presence of laccase by one of the following polyphenols in the presence of air: gallic acid (GA), vanillic acid (VA) and catechol (1,2–DHB). Enzyme was added at constant loading (24 kg ton⁻¹), 1% pulp consistency, 0.005% CMC, pH = 6.3 ± 0.5 and 2 mM of mediator. CPX content was assessed at two levels (0% and 0.005%). Treated pulps were analyzed by different mechanical tests (ring crush, mullen, corrugating medium test (CMT) flat crush of corrugating medium test and tension). An improvement in these parameters was obtained by biopolymer coupling and selected mediator. When using GA, three parameters increased more than 40%, while ring crush increased 120%. For the case of VA, properties were enhanced from 74% to 88% when CPX was added. For 1,2–DHB, there was not found a statistically significant difference between the results in the presence of CPX. Scanning electron microscopy, confocal microscopy, FTIR and ¹³C NMR were used in all papers in order to evaluate grafting. Hence, it was possible to correlate polymerization with an improvement of paper’s mechanical properties.

A novel strategy to immobilize bacteria on polymer particles for efficient adsorption and biodegradation of soluble organics

A novel strategy was used to immobilize bacterial cells on the surface of functional polymer particles for the efficient adsorption and biodegradation of organics in wastewater. First, the bacterial cells were aggregated using a vinyl-containing pre-polymer, and the obtained bacteria-pre-polymer complex was then used as a particle stabilizer to construct a stable Pickering emulsion of functional cross-linking monomers and hydrophobic superparamagnetic iron oxide nanoparticles (the oil phase) in water. After polymerization, the bacteria-pre-polymer complex was covalently fixed to the surface of the polymer particles. Two species of bacterial cells (Pseudomonas putida andParacoccus denitrificans) were used as models to study their removal capacity for phenol and DMF, respectively. Batch experiments showed that the as-prepared magnetic bacteria-polymer (MPB) composites could efficiently remove organics from the aqueous solutions, and the encapsulated iron oxide nanoparticles enabled the MPB composites to be magnetically separated.

Effect of surface treatments of jute fibers on the microstructural and mechanical responses of poly(lactic acid)/jute fiber biocomposites

The effect of surface treatment of jute fibers on matrix/fiber interface adhesion in PLA/jute fiber biocomposites was explored in terms of mechanical, morphological, thermal and thermo mechanical properties.