Enzymatic modification of lignin and its application in phenol-formaldehyde based polymers

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This proposal addresses the modification of lignin using an enzymatic approach, and will complement research programs on chemical modification of lignin in progress elsewhere in Canada. The modification of natural polymers such as lignin with enzymes is an environmentally-friendly alternative to the harsher chemical method. Moreover, the specificity of enzymes is exploited as they target specific functional groups on polymer surfaces without destroying the polymer itself. An intensive screening program of wood-decay fungi collected from the Boreal Forest and housed in the Mycological Herbarium at Lakehead University will be conducted to search for enzymes involved in lignin modification (oxidation and hydrolysis reactions).-of particular interest, are enzymes that specifically cleave-off methyl (demethylation) and methoxyl groups (dernethoxylation) from Kraft and steam explosion-derived lignins. To our knowledge, enzymes of this activity type have not yet been described in the scientific literature, although there is evidence that methanol (result of methyl removal) is liberated from lignin by ligninolytic fungi. As lignin is a highly methylated natural polymer, specific enzymes are likely associated with demethylation of lignin. These will be sought through screening. Fungi (and enzyme: activity associated with demethylation of lignin can be assayed by measuring methanol released. The objective of this proposal is to discover and isolate microbial enzymes that can modify lignin through demethylation reactions, and to elucidate this mechanism. The lignin demethylating enzyme(s) will be produced on a large scale, and the physicochemical properties of the crude, as well as in the purified form, characterised as this information is vitally important in downstream studies on the enzymatic modification of lignin. The enzyme(s) will be employed in the demethylation of lignin and conditions optimised, and the demethylated product assessed for reactivity as a substitute for phenol in formaldehyde polymer applications. The overall outcome of