Industrial utilization of lignin is of high interest since it represents around 30% of all nonfossil-based carbon sources worldwide. For various applications of lignosulfonates such as for dispersants or adhesives a larger molecular weight is essential. Here, we investigated laccase-catalyzed polymerization of lignosulfonate directly from the pulp and paper industry in the presence and absence of natural and synthetic mediators with and without oxygen supply. For example, laccase-mediated polymerization in the presence of a 2.5 mM TEMPO as mediator with a 10 cm 3 min −1 oxygen flow rate led to a 12-fold increase of the molecular weight, while without TEMPO a 13-fold increase was achieved. In contrast, without an external oxygen supply, only a 7-fold increase in molecular weight was achieved compared to a 4-fold increase for the TEMPO−laccase system. Fluorescence intensity, phenol content, and size exclusion chromatography measurements indicate that generally in the presence of high concentrations of mediators, such as TEMPO, vanillin, HBT, and 2,6-dimethoxyphenol, oxidation of other structural units in lignosulfonates may counteract desired polymerization reactions. In summary, for laccase-catalyzed polymerization of lignosulfonates, an external oxygen supply was found to be much more beneficial than the presence of laccase mediators.

Enzymatic polymerization of lignin is an environmentally-friendly and sustainable method that is investigated for its potential in opening-up new applications of one of the most abundant biopolymers on our planet. In this work, the laccase from Myceliophthora thermophila was successfully immobilized onto Accurel MP1000 beads (67% of protein bound to the polymeric carrier) and the biocatalyzed oxidation of Kraft lignin (KL) and lignosulfonate (LS) were carried out. Fluorescence intensity determination, phenol content analysis and size exclusion chromatography were performed in order to elucidate the extent of the polymerization reaction. The collected results show an 8.5-fold decrease of the LS samples' fluorescence intensity after laccase-mediated oxidation and a 12-fold increase of the weight average molecular weight was obtained.

Pharmaceuticals contaminate the environment for several reasons, including metabolic excretion after intake, industrial waste and improper disposal. The narcotic drug morphine is commonly utilized for chronic pain management, and the distribution of morphine in aqueous systems and in waste waters is of high concern. Here, the removal of morphine by a laccase from Myceliophthora thermophila both in its free form as well as immobilized on Accurel MP1000 beads was investigated. Complete morphine elimination was achieved within 30 min for the free and the immobilized enzyme (70% bound protein) for concentrations between 1 and 1,000 mg L according to LC-TOF mass spectrometry analysis. Higher morphine concentrations up to 60 g L were also tested and total elimination was achieved within 6 h. Therefore, laccases are ideal candidates for removing morphine from aqueous systems.

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