Catalytic Degradation Of Lignin Model Compounds By Laccase In The System Constructed By Surfactant

As an organic macromolecule polymer, lignin is widely distributed in nature andpossesses a very complex structure. Lignin is often regarded as a byproduct of woodhydrolysis industry and paper industry, and the byproduct is often released into theenvironment without being disposed of effectively, which can cause environmentalpollution. The molecular composition of lignin is very complex，and it can not becompletely degradated by single methods, so most of the current studies focus on thedegradation of lignin model compounds.Biodegradable enzymes such as lignin peroxidase, manganese peroxidase andlaccase can degrade lignin model compounds, but the degradation efficiency ofenzyme is not high when only enzyme exits. So people tend to add additives toimprove the degradation efficiency of lignin-degrading enzymes. This experiment wasdone aiming to study the performance of lignin model compounds catalyzed bylaccase in different systems constructed by surfactants. The study included thecatalytic properties of laccase to pyrocatechol in micellar system, and the catalyticproperties of laccase to veratryl alcohol in reverse micelle system. Experimentalresults showed that:1) The micelles constructed by mono-RL and Triton X-100in1CMC couldpromote the degradation of pyrocatechol, and the degradation rate of substratereduced when micelle concentration of them was3CMC. CTAB always inhibited thedegradation of pyrocatechol.2) Further studies on reaction time, laccase content, substrate concentration andmediator/substrate ratio showed that, mono-RL micellar system in1CMC couldeffectively promote the degradation of pyrocatechol.3) The study on the activity of laccse showed that, anionic surfactant mono-RLand non-ionic surfactant Triton X-100had a positive effect in increasing the enzymeactivity, while cationic surfactant CTAB had an opposite effect on the enzyme activity.1CMC mono-RL micellar system not only improved the activity of laccase, but alsoenhanced the stability of laccase.4) The critical micelle concentration (CMC) of CTAB, Tween80, and mono-RLin isooctane/hexanol (V:V,1:1) were0.5mM,0.01mM, and0.05mM respectively. The conductivity analysis showed that the optimum moisture content of the reversemicelle of CTAB, Tween80, and mono-RL were15,5and40respectively. The resultsshowed that, biosurfactant mono-RL not only possessed smaller CMC, but alsopossessed a large water content compared with the chemical surfactant CTAB andTween80, so a more advantageous environment for laccase was provided bymono-RL.5) The enzymatic hydrolysis in the reverse micelles constructed by mono-RLshowed that, the best reaction conditions for the degradation of veratryl alcohol wereas follows:[mono-RL]=20mM，Wo=40，pH=5. Experimental results showed that, thereverse micelle was more effective in promoting the degradation of substratecatalyzed by laccase than the micelle.6) The fluorescence analysis on the interaction between mono-RL and laccase inreverse micelle showed that, when Wo was increased to40, laccase could besolubilized within the micro-water nuclear, which avoided the contact betweenlaccase and organic solvents, thereby increasing the activity and stability of laccase.