Biological Enzyme Oxidize Galactomannan As A Paper Strengthening Agent

With the increasing demand for paper quality,paper strengthening agents,a kind of auxiliary chemicals,are widely used in the paper industry,as they benefit the paper properties.In the face of increasingly serious environmental problems,it is of great significance to develop a green and environmentally friendly method of paper strengthening agents.In this study,galactomannans,which are a type of plant polysaccharide,were oxidized by using enzyme catalytic system to prepare paper strengthening agents.The reaction conditions were optimized according to the properties of paper.At last,the structural characterization of modified galactomannan was determined by elemental analysis,FT-IR,and CP/MAS13C-NMR analyses.Galactomannans were oxidized by using a laccase and TEMPO-mediated air-oxidation system.The influence of the oxidation conditions,including the laccase doses,oxidation times,and amounts of oxidizing system,on the properties of the paper were investigated.The optimal conditions were as follows:a 60 U/g enzyme dosage;6-hour oxidization time and a 0.1g TEMPO dosage.When compared with the control paper,the tensile index and folding endurance have been improved by 28.42%and 88.02%,respectively,when 1.5%oxidized galactomannans were used,and for the recycled paper,the increment could reach 43.85%and 126.97%correspondingly.Also,the results of the elemental,FT-IR,and CP/MAS13C-NMR analyses demonstrated that some of the hydroxyl of the galactomannans had been transformed into the carboxyl and aldehyde groups.Galactomannans were oxidized by using galactose oxidase with the help of horseradish peroxidase(HRP)and catalase,then prepare paper strengthening agents by oxidation with a small amount of hydrogen peroxide.The optimal conditions were investigated by testing the properties of paper,and minimize the dosage of hydrogen peroxide.When the enzyme dosage is 50 U/g and hydrogen peroxide concentration is 0.4%,the properties of paper could be improved evidently with a less hydrogen peroxide using.The tensile index and folding endurance have been improved by 23.50%and 110.31%,respectively.The results of the elemental,FT-IR,and CP/MAS13C-NMR analyses demonstrated that some of the hydroxyl of the galactomannans had been transformed into the carboxyl and aldehyde groups.