Effect of Lipase and Laccase on the Properties of Colloidal Substances Released from ONP

The effects of enzymatic treatments of dissolved and colloidal substances (DCS) released from the old newspaper pulp (ONP) have been investigated. Lipase gave a complete hydrolyzation of triglycerides into free fatty acids. The untreated DCS gave no significant decrease in tensile strength, because of the relatively small addition. A treatment of the DCS with Lipase gave a higher extractives content and a tensile strength on the same level as the reference. The hydrolysis of triglycerides by Lipase could result in improved hydrophilicty of the fibers as measured by contact angle. This in turn resulted in improved bonding ability and tensile index. In this paper, we show that laccase was used to remove the lipophilic compounds from paper pulp. The treatment of laccase on ONP could result in the impaired tensile strength of sheets. The wet strength of sheets was improved due to the laccase action.