Phenoloxidase-lignin adhesive

The phenoloxidase-lignin adhesive is not only applicable as thermosetting adhesive but also as a cold-curing system. 

Milled wood lignin was mixed with the crude enzyme solution of Tram-ties versicolor extracellular phenoloxidases produced on spent sulfite liquor in a ratio of approximately 2 1. This comprised the main part of the two-component bio-adhesive. Industrial particles were bonded with 15% bioadhesive under conventional pressing conditions to have 19 mm particle boards (40 x 50 cm) of the properties described in Table IV. The bonding reaction (crosslinking) took place in aqueous solution at room temperature. If conventional pressing technology is applied, the temperature should be elevated in order to maintain water evaporation within a reasonable press time. 

Room-Temperature Curing Adhesives Based on Lignin and Phenoloxidases... 

The underlying reaction mechanism is the crosslinking of lignin via oxidative polymerization catalyzed by the phenoloxidase. The production of this adhesive includes the total utilization of waste lignins a) directly as one component of the binding system and b) indirectly as nutrient source of the phenoloxidase-producing fungi. 

Composition of the adhesive One part spray-dried, milled sulfite liquor containing ca. 20% sugar and 1.5 parts concentrated culture filtrate of Trametes versicolor (grown on 0.1% organosolv lignin in a 25 L fermenter), containing 420 U/mL phenoloxidase activity. 

Haars, A. Kharazipour, A. Huttermann, A. Two-component wood adhesives based on lignin and phenoloxidases. Abstr., 3rd Inti. Conf. Biotechnol. Pulp Paper Industry, Stockholm, 1986. 

---