A new solution to pitch problems in the pulp and paper industry using the laccase-mediator system

Lipophilic extractives in wood and other lignocellulosic materials exert a highly negative impact in pulp and paper manufacturing causing the so-called pitch deposits. As an alternative to physicochemical methods, lipases have been successfully applied to softwood mechanical pulping.1 However, the enzymes and microbial inocula available till present are only effective on some raw materials and processes. Recently, we have shown for the first time the effectiveness of the laccase-mediator system (LMS) in removing pulp lipids regardless the pulping process and raw material used.2,3,4 In these studies, pulp samples from eucalypt kraft pulping, spruce thermomechanical pulping (TMP), and flax soda-anthraquinone (AQ) pulping were treated with laccase in the presence of 1-hydroxybenzotriazole as redox mediator. The gas chromatography/mass spectrometry analyses of the extracts from the enzymatically-treated pulps revealed that most of the lipophilic compounds were efficiently removed by the LMS treatment. Free and conjugated sitosterol, the main responsible for pitch deposits in eucalypt kraft pulp manufacturing, was completely removed. In spruce TMP pulp, LMS degraded most of the resin acids, sterol esters and triglycerides. In the flax soda-AQ pulp, sterols and long-chain fatty alcohols were almost completely removed. Small amounts of oxidation products (including 7-oxositosterol and stigmasta-3,5-dien-7-one mainly derived from free and esterified sitosterol, respectively) were identified. Pulp and papermaking properties of the enzymatically-treated pulps were also evaluated. It is possible to conclude that LMS treatment is an efficient method to remove pitch-causing lipophilic compounds from hardwood, softwood and nonwood paper pulps, at the same time that their lignin content is reduced.

Peer reviewed