REDUCING THE CONTENT OF VOCS OF SOFTWOOD KRAFT LIGNINS FOR MATERIAL APPLICATIONS

摘要

Three laccases functioning in mild acidic and one in slightly alkaline (pH 8) conditions were evaluated in order to reduce small-molecular phenolic VOCs of kraft lignins, which could be used in ligninatural fibers composites. The potential of a sulfhydryl oxidase to catalyze the oxidation of sulphur containing VOCs (thiols) was also tested in combination with the laccase catalyzed oxidation at pH 8. In addition, oxidation at alkaline pH at room temperature that may induce polymerization of phenolics in an analogous manner to the laccasecatalysed reaction was investigated. Enzyme reactivity towards lignins was evaluated as consumption of oxygen in the reaction solution. The effect of treatments on VOC reduction was determined both by sensing (odorimetry) and chemical (thermal desorption GC/MS, SEC) analyses. Laccases Lcc2 and MaL from Thielavia arenaria and Melanocarpus albomyces, respectively, showed potential in reducing odors. The most promising results were obtained by oxidizing lignin at alkaline pH. However, the odor threshold values of the main VOC compounds are extremely low, which poses a challenge to VOC reduction.