1 Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT, Utrecht, The Netherlands.
2 Current address: Protein Production Team, VTT Technical Research Center of Finland Ltd, Tietotie 2, 02150, Espoo, Finland.
3 Centre for Functional and Structural Genomics, Concordia University, Sherbrooke St. W. Montreal, QC, H4B 1R6, Canada.
4 Laboratory of Food Chemistry, Wageningen University and Research, Bornse Weilanden 9, 6708 WG, Wageningen, The Netherlands.
5 Department of Chemistry, Technical University of Denmark, Building 207, Kemitorvet, DK-2800, Denmark.

Feruloyl esterases (FAEs) and acetyl xylan esterases (AXEs) are important enzymes for plant biomass degradation and are both present in Carbohydrate Esterase family 1 (CE1) of the Carbohydrate-Active enZymes database. In this study, ten novel fungal CE1 enzymes from different subfamilies were heterologously produced and screened for their activity towards model and complex plant biomass substrates. CE1_1 enzymes possess AXE activity, while CE1_5 enzymes showed FAE activity. Two enzymes from CE1_2 and one from CE1_5 possess dual feruloyl/acetyl xylan esterase (FXE) activity, showing expansion of substrate specificity. The new FXEs from CE1 can efficiently release both feruloyl and acetyl residues from feruloylated xylan, making them particularly interesting novel components of industrial enzyme cocktails for plant biomass degradation.