Application of surfactants in papermaking industry and future development trend of green surfactants.

In this work, the application of chemical surfactants, including cooking aids, detergents, surface sizing agents, and deinking agents as core components, is introduced in the wet end of pulping and papermaking. This method for the combined application of enzymes and surfactants has expanded, promoting technological updates and improving the effect of surfactants in practical applications. Finally, the potential substitution of green surfactants for chemical surfactants is discussed. The source, classification, and natural functions of green surfactants are introduced, including plant extracts, biobased surfactants, fermentation products, and woody biomass. These green surfactants have advantages over their chemically synthesized counterparts, such as their low toxicity and biodegradability. This article reviews the latest developments in the application of surfactants in different paper industry processes and extends the methods of use. Additionally, the application potential of green surfactants in the field of papermaking is discussed. KEY POINTS: • Surfactants as important chemical additives in papermaking process are reviewed. • Deinking technologies by combined of surfactants and enzymes are reviewed. • Applications of green surfactant in papermaking industry are prospected.

[Display of glucose oxidase on Bacillus subtilis spore surface and preparation for enzyme electrode].

Glucose biosensor is currently the most common electrochemical biosensor. Most glucose biosensors are prepared by modifying glucose oxidase on the electrode surface. However, in the process of electrode immobilization, enzyme purification is required, which increases the cost and has become a bottleneck in the field of development of immobilized enzyme electrodes. In this study, glucose oxidase (GOD) was displayed on the surface of Bacillus subtilis using the spore capsid protein CotX as an anchor protein. By Western blotting analysis, immunofluorescence analysis and enzyme activity detection, GOD was effectively expressed on the surface of spores, and recombinant spores (Spore-GOD) were obtained by fermentation. The graphene oxide/prussian blue deposition film modified glassy carbon electrode was prepared by the drop coating method and the electrodeposition method. The surface of the modified electrode was fixed with Spore-GOD, and finally covered with a layer of Nafion solution to make an electrochemical biosensor for sensitive determination of glucose. The cyclic voltammogram of glucose on the enzyme electrode sensor showed a well-defined oxidation peak at 0.42 V, and the redox peak current has a good linear relationship with the glucose concentration in the range of 0.1-7.0 mmol/L. The calibration curve equation is: I=1.305C(glucose)+3.639 (R²=0.992 9), and its detection limit is 7.5 µmol/L (S/N=3). This modified electrode has good conductivity, stability and reproducibility, and can be used for the analysis and determination of glucose.