Study On The Activation Of Corn Stalk Lignin By Laccase

In this paper, corn stalk lignin was activated by laccase and laccase/mediator system under aerobic condition. The issue that corn stalk lignin is insoluble in water was effectively solved by using mixed solvents system. Activation treatment increased the hydroxyl content of corn stalk lignin, reduced the relative molecular mass and improved the activity of reaction.(1) First, corn stalk lignin was activated by laccase, and three mixed solvents were used which were dioxane/water, polyethylene glycol/water and sulfonate lignin/water. Fourier transform infrared spectroscopy (FTIR), UV-visible spectrophotometer, GPC and TGA were applied for microscopic analysis and characterization. The effects of activation conditions, such as activation time, pH value of the system, activation temperature and dosage of laccase had been carried out. The best activation conditions of corn stalk lignin activation treatment by laccase were that the activation time was 1.5-2 hours, the pH value was 4.0, the activation temperature was 40℃ and the dosage of laccase was 25U/g.(2) Corn stalk lignin was activated by laccase under the best activation conditions in three mixed solvents, then compared and analysised the treatment effects of the activation treatment in three mixed solvents. The best mixed solvents was polyethylene glycol/water. In this mixed solvent, the best activation conditions of corn stalk lignin activation treatment by laccase were that the activation time was 1.5 hours, the pH value was 4.0, the activation temperature was 40℃ and the dosage of laccase was 25U/g. The hydroxyl content of corn stalk lignin was increased from 3.6% to 4.3% by the activation treatment. The DSC test proved that the esterification reaction capability of activated corn stalk lignin and saturated fatty acids increased.(3) HBT, lilac aldehyde and vanillin were choosen to be the mediator. Corn stalk lignin was activated by laccase/mediator system under the best activation conditions in polyethylene glycol/water mixed solvent. The experiments showed that the activation treatment of laccase/mediator systems could further degraded corn stalk lignin and caused chain scission and degradation of high molecular weight lignin. The hydroxyl content of lignin activated by laccase/HBT system was increased from 3.6%to 4.6%. The content of high molecular weight lignin was reduced. Compared with the corn stalk lignin activated by laccase, the esterification reaction capability of saturated fatty acids and corn stalk lignin activated by laccase/HBT further increased.