Lignin modification by MetZyme ® LIGNO™ was characterized by size exclusion chromatography, UV spectroscopy, and dynamic light scattering for monitoring particle size of solubilized lignin. In this article, main characteristics of this enzyme as well as its action on bulk lignin coming from an industrial process are demonstrated. This enzyme can function at pH values as high as 10–11 and at elevated temperatures, addressing lignin at its soluble state. A Finnish biotechnology company, MetGen Oy, that designs and supplies industrial enzymes, has developed and brought to market several lignin oxidizing enzymes, including an extremely alkaline lignin oxidase MetZyme ® LIGNO™, a genetically engineered laccase of bacterial origin. However, their application was limited to ambient pH, where lignin is poorly soluble in water. Oxidative enzymes (i.e., laccases and peroxidases) have long been proposed as a potentially promising tool in lignin depolymerization. Controlled fragmentation of lignin could lead to its use in higher value products such as binders, coatings, fillers, etc. Main hurdles of lignin valorization are its diverse chemical composition, recalcitrance, and poor solubility due to high-molecular weight and branched structure.
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