Jiajia Fu

Laccase: a green catalyst for the biosynthesis of poly-phenols

Abstract Laccases (benzene diol: oxidoreductases, EC 1.10.3.2) are able to catalyze the oxidation of various compounds containing phenolic and aniline structures using dissolved oxygen in water. Laccase structural features and catalytic mechanisms focused on the polymerization of aromatic compounds are reported. A description about the most recent research on the biosynthesis of chemicals and polymers is made. Selected applications of this technology are considered as well as the advantages, shortcomings and future needs related with the use of laccases.

Enzymatic colouration with laccase and peroxidases : recent progress

Enzymes have received significant attention as alternative catalysts to chemical auxiliaries in textile processing. For example, laccases and peroxidises are promising alternatives for bleaching and denim stone washing processes. Similarly, the ability to oxidise different phenolic substrates and dye precusors resulting in the formation of different coloured polymeric molecules is being exploited for developing green chemistry dyeing processes. The enzymatic process is simpler than conventional coloration processes, giving economic and environmental benefits. In this review, the applications of laccase and peroxidise enzymes in dyeing processes of various textile meterials is discussed.

Practical insights on enzyme stabilization

Abstract Enzymes are efficient catalysts designed by nature to work in physiological environments of living systems. The best operational conditions to access and convert substrates at the industrial level are different from nature and normally extreme. Strategies to isolate enzymes from extremophiles can redefine new operational conditions, however not always solving all industrial requirements. The stability of enzymes is therefore a key issue on the implementation of the catalysts in industrial processes which require the use of extreme environments that can undergo enzyme instability. Strategies for enzyme stabilization have been exhaustively reviewed, however they lack a practical approach. This review intends to compile and describe the most used approaches for enzyme stabilization highlighting case studies in a practical point of view.

Bamboo fibre processing: insights into hemicellulase and cellulase substrate accessibility

A biological approach for degumming bamboo substrates has been assessed. The ability of various commercially available enzymes, including cellulase, xylanase, pectinase and mannanase, to hydrolyze bamboo powders was investigated. In addition, a commercial cellulase preparation was applied onto bamboo fibre bundles obtained by natural retting. It was found that almost all enzymes applied can use bamboo material as a substrate. Mild autoclave pre-treatment can enhance reducing sugar yield from different enzyme treatments. A most pronounced effect was observed with cellulase treatment in which the hydrolysis degree increased 1.7 fold as measured by reducing sugars for autoclave pre-treated bamboo powders versus non-treated powders after only a short period of incubation. The combined treatment of hemicellulase preparations showed no effect on the hydrolysis of bamboo substrates. The effect of autoclave pre-treatment on cellulase-treated samples was confirmed by the increase of sugar yield, protein absorption as well as by the enhancement of surface modification and enzyme penetration observed by CLSM (confocal laser scanning microscopy). This work establishes a base for future studies to develop enzymatic hydrolysis of bamboo materials, making them suitable for textile processing.

Enzymatic processing of protein-based fibers

Wool and silk are major protein fiber materials used by the textile industry. Fiber protein structure-function relationships are briefly described here, and the major enzymatic processing routes for textiles and other novel applications are deeply reviewed. Fiber biomodification is described here with various classes of enzymes such as protease, transglutaminase, tyrosinase, and laccase. It is expected that the reader will get a perspective on the research done as a basis for new applications in other areas such as cosmetics and pharma.

Bio-processing of bamboo fibres for textile applications: a mini review

This review addresses the potential biotechnological techniques for textile fibre extraction (degumming), mainly focusing on bamboo, one of the main and recently developed textile natural fibres in China. The latest developments in microbial and enzymatic processing for ecological fibre extraction as well as the development of a molecular technique for natural fibre bio-treatment are highlighted.

PEGylation greatly enhances laccase polymerase activity

Laccase catalyzes the oxidation and polymerization of phenolic compounds in the presence of oxygen. Herein, we report for the first time that a previous PEGylation of laccase enhances the polymerase activity 3‐fold compared with the reaction of the native enzyme, as confirmed by UV/Vis spectroscopy. The polymerization of catechol increased only 1.5‐fold if poly(ethylene glycol) (PEG) was added to the medium reaction. Molecular‐dynamics simulations suggest the formation of a miscible complex of polycatechol and PEG, which is responsible to push the reaction forward. In a negative control experiment set, all catalysts were entrapped inside polyacrylamide gels and here the native laccase showed a relatively higher activity. These results suggest that the mobility of PEG is a key feature for the enhancement of the reaction.

The electromagnetic interference shielding performance of continuous carbon fiber composites with different arrangements

Composites with different arrangements of continuous carbon fibers, with the poly(ethylene terephthalate)-spunbond nonwoven fabrics as substrates, were fabricated for optimization of electromagnetic interference shielding performance. Effects of these structural parameters, including array spacing, the number of layers, and overlap angle, were investigated within the frequency band of 30 MHz–1.5 GHz, which includes the major electromagnetic wave frequency from daily electronic device or apparatus. Within 30 MHz–750 MHz, shielding effectiveness was fortified with the decrease of array spacing and the increase of the number of layers owning to the increase of the continuous carbon fiber content. Whereas, within the frequency band of 750 MHz–1.5 GHz, the number of layers presented little effect on the shielding performance reasoning that the impact of continuous carbon fiber orientation was more significant than that of continuous carbon fiber content. While the array spacing was 8 mm and the maximum value of shielding effectiveness for the two-layer composites was 46.8 decibel at frequency of 1000 MHz. For multilayer composites, shielding performance was improved by synergistic effects of overlap angle and array spacing. Hence, composite with three layers, array spacing of 12 mm and overlap angle of 0°–0°–45° achieved the highest electromagnetic interference shielding properties of 60.49 decibel, corresponding frequency of 1.0 GHz. The results of this work demonstrated a potentially efficient and economical way to fabricate the electromagnetic interference shielding composites with less content of continuous carbon fiber and to simultaneously achieve superb shielding performance. This work will be significant for further study in the electromagnetic interference shielding composite industry in the near future.

The effect of high-energy environments on the structure of laccase-polymerized poly(catechol)

The laccase polymerization of catechol was performed using different reactors namely a water bath (WB), an ultrasonic bath (US) and a high-pressure homogenizer (HPH). The total content of free OH and the MALDI-TOF spectra of polymers obtained demonstrated that reactions are favored in the presence of high-energy environments. Higher conversion yields and polymerization degrees (DP) were obtained after polymerization using US or HPH. Molecular dynamic simulation studies supported these findings by revealing a more open enzyme active site upon environments with high molecular agitation. The higher mass transport generated by US and HPH is the main feature responsible for a higher substrate accessibility to the enzyme which contributed to produce longer polymers.

Antimicrobial activity and mechanism of PLA/TP composite nanofibrous films

Electrospinning is conducted with polylactic acid (PLA) and tea polypheno (TP) to obtain PLA/TP composite nanofibrous films with high antimicrobial activity. An investigation of the composition, antimicrobial activity, and mechanism of these composite nanofibrous films was conducted by using infrared spectroscopy (FT-IR), inhibition zone method, fluorescence activated cell sorter (FACS), and transmission electron microscope (TEM). IR spectra results showed that TP and PLA composited well through valence bonds in PLA/TP composite nanofibrous films. Ranges of the inhibition zone for the growth of Escherichia coli (E. coli) and Staphylococcus (Staphylococcus aureus) were 3.67 and 3.71 cm in pure PLA nanofibrous films, but 5.17 and 5.67 cm in PLA/TP composite nanofibrous films, respectively. Results indicated that the antimicrobial activity of PLA/TP composite nanofibrous films were much higher than that of pure PLA nanofibrous films. Meanwhile, the antimicrobial activity against S. aureus was also slightly higher than E. coli. FACS results showed that the positive rate of PLA/TP composite nanofiber films was greater than that of pure PLA nanofibrous films, increasing from 1.45 and 0.78% to 9.26 and 6.47% against S. aureus and E. coli, respectively. The result of TEM indicated that PLA/TP composite nanofibrous films led to the death of bacteria by destroying the integrity of cell membrane.