Novel lytic polysaccharide monooxygenases (LPMOs) degrading hemicellulose in plant cell wall

Lignocellulosic plant cell walls, being the largest reservoir of carbohydrates on earth, provide a potential alternative to fossil feedstocks for a greener economy. Lignocellulose consists of a complex and heterogeneous network of cellulose, hemicelluloses and lignin, making biomass recalcitrant and resistant to enzymatic hydrolysis. Cellulose, the major carbohydrate component, is embedded in a hemicellulose matrix, primarily composed of xylan or glucomannan in secondary cell walls and also of xyloglucan in primary cell walls. In nature, plant cell walls are degraded by a number of biomass-degrading bacteria and fungi. Litter-decomposers and plant pathogens secrete a set of glycoside hydrolases and redox enzymes, such as lytic polysaccharide monooxygenases (LPMOs), which target the cleavage of cellulose and various hemicelluloses [1]. Glycoside hydrolases cover many substrate specificities and are able to hydrolyze cellulose and various hemicelluloses. LPMOs primarily target crystalline cellulose, making it susceptible to further degradation by glycoside hydrolases. Recently, however, two AA9 LPMOs, NcLPMO9C from Neurospora crassa [2-3] and PaLPMO9H from Podospora anserina [4] have been reported to act on water-soluble cello-oligosaccharides and hemicellulose, providing a first glimpse of additional substrate specificities. In this work, we expand further the repertoire of hemicellulose-active AA9 LPMOs by presenting the saccharification of various hemicellulosic cell wall components such as xyloglucan and glucomannan by several LPMOs.

References:

[1] Horn et al. (2012) Biotechnol Biofuels 5(1):45.

[2] Isaksen et al. (2014) J Biol Chem 289(5):2632–2642.

[3] Agger et al. (2014) Proc Natl Acad Sci U S A. 111(17):6287-6292.

[4] Bennati-Granier et al. (2015) Biotechnol Biofuels 8:90.