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Biotechnol Biofuels. 2015 Jun 20;8:90. doi: 10.1186/s13068-015-0274-3. eCollection 2015.

Substrate specificity and regioselectivity of fungal AA9 lytic polysaccharide monooxygenases secreted by Podospora anserina.

Author information

1
INRA, UMR1163 Biodiversité et Biotechnologie Fongiques, Faculté des Sciences de Luminy, ESIL Polytech, F-13288 Marseille, France.
2
Polytech Marseille, Aix Marseille Université, F-13288 Marseille, France.
3
Institute of Chemistry, Slovak Academy of Sciences, 84538 Bratislava, Slovakia.
4
INRA, Plateforme BIBS, Unité de Recherche Biopolymères, Interactions, Assemblages, 44316 Nantes, France.
#
Contributed equally

Abstract

BACKGROUND:

The understanding of enzymatic polysaccharide degradation has progressed intensely in the past few years with the identification of a new class of fungal-secreted enzymes, the lytic polysaccharide monooxygenases (LPMOs) that enhance cellulose conversion. In the fungal kingdom, saprotrophic fungi display a high number of genes encoding LPMOs from family AA9 but the functional relevance of this redundancy is not fully understood.

RESULTS:

In this study, we investigated a set of AA9 LPMOs identified in the secretomes of the coprophilous ascomycete Podospora anserina, a biomass degrader of recalcitrant substrates. Their activity was assayed on cellulose in synergy with the cellobiose dehydrogenase from the same organism. We showed that the total release of oxidized oligosaccharides from cellulose was higher for PaLPMO9A, PaLPMO9E, and PaLPMO9H that harbored a carbohydrate-binding module from the family CBM1. Investigation of their regioselective mode of action revealed that PaLPMO9A and PaLPMO9H oxidatively cleaved at both C1 and C4 positions while PaLPMO9E released only C1-oxidized products. Rapid cleavage of cellulose was observed using PaLPMO9H that was the most versatile in terms of substrate specificity as it also displayed activity on cello-oligosaccharides and β-(1,4)-linked hemicellulose polysaccharides (e.g., xyloglucan, glucomannan).

CONCLUSIONS:

This study provides insights into the mode of cleavage and substrate specificities of fungal AA9 LPMOs that will facilitate their application for the development of future biorefineries.

KEYWORDS:

AA9; Biomass; Biorefinery; Cellobiose dehydrogenase; Cellulose; Hemicellulose; LPMO; Lignocellulose; Oxidative cleavage; Oxidized cello-oligosaccharides

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