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Biotechnol Biofuels. 2017 Sep 12;10:215. doi: 10.1186/s13068-017-0903-0. eCollection 2017.

The yeast Geotrichum candidum encodes functional lytic polysaccharide monooxygenases.

Author information

1
INRA, Aix Marseille University BBF, Biodiversité et Biotechnologie Fongiques, 13288 Marseille, France.
2
INRA, UR1268 Biopolymères Interactions Assemblages, 44316 Nantes, France.
3
Architecture et Fonction des Macromolécules Biologiques, UMR7857, CNRS, Aix-Marseille University, 13288 Marseille, France.
4
USC1408, Architecture et Fonction des Macromolécules Biologiques, INRA, 13288 Marseille, France.
5
Department of Biological Sciences, King Abdulaziz University, Jedda, 21589 Saudi Arabia.

Abstract

BACKGROUND:

Lytic polysaccharide monooxygenases (LPMOs) are a class of powerful oxidative enzymes that have revolutionized our understanding of lignocellulose degradation. Fungal LPMOs of the AA9 family target cellulose and hemicelluloses. AA9 LPMO-coding genes have been identified across a wide range of fungal saprotrophs (Ascomycotina, Basidiomycotina, etc.), but so far they have not been found in more basal lineages. Recent genome analysis of the yeast Geotrichum candidum (Saccharomycotina) revealed the presence of several LPMO genes, which belong to the AA9 family.

RESULTS:

In this study, three AA9 LPMOs from G. candidum were successfully produced and biochemically characterized. The use of native signal peptides was well suited to ensure correct processing and high recombinant production of GcLPMO9A, GcLPMO9B, and GcLPMO9C in Pichia pastoris. We show that GcLPMO9A and GcLPMO9B were both active on cellulose and xyloglucan, releasing a mixture of soluble C1- and C4-oxidized oligosaccharides from cellulose. All three enzymes disrupted cellulose fibers and significantly improved the saccharification of pretreated lignocellulosic biomass upon addition to a commercial cellulase cocktail.

CONCLUSIONS:

The unique enzymatic arsenal of G. candidum compared to other yeasts could be beneficial for plant cell wall decomposition in a saprophytic or pathogenic context. From a biotechnological point of view, G. candidum LPMOs are promising candidates to further enhance enzyme cocktails used in biorefineries such as consolidated bioprocessing.

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