Abstract text: Plant cell walls have for hundreds of millions of years provided support and protection for plants. Today, plant cell walls are the most abundant renewable resource in the world with great potential for utilisation in sustainable applications. The heterogeneity of plant cell walls is a key issue to address, as components, composition, and structure differ within and between species. Targeted treatments are needed to overcome this, like enzymatic cocktails. While many enzymes have been studied and applied, the relatively new families of lytic polysaccharide monooxygenases (LPMOs) show promise. LPMOs have been shown to oxidise cellulose, chitin, and starch, with additional substrates occasionally reported. Here, we present a systematic investigation of LPMO oxidation of mannan.

The activity of three different LPMOs was tested on four mannan substrates, and two samples of glucomannan, each combined with a different xylan. Oxidation was observed exclusively with glucomannan, indicating LPMOs require one or more glucosyl unit(s). Furthermore, the cooperation between cellobiose dehydrogenase (CDH) with a LPMO on glucomannan was demonstrated. CDH was shown to accept an assortment of mono- and polysaccharides, and, interestingly, several LPMO-oxidised substrates. These findings demonstrate the cooperation of the LPMO and CDH and provide further insight into LPMO oxidations of substrates.