Polysaccharide utilization loci-driven enzyme discovery reveals BD-FAE: a bifunctional feruloyl and acetyl xylan esterase active on complex natural xylans

Lisanne Hameleers, Leena Penttinen, Martina Ikonen, Léa Jaillot, Régis Fauré, Nicolas Terrapon, Peter J. Deuss, Nina Hakulinen, Emma R. Master, Edita Jurak*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

7 Citations (Scopus)
66 Downloads (Pure)


Background: Nowadays there is a strong trend towards a circular economy using lignocellulosic biowaste for the production of biofuels and other bio-based products. The use of enzymes at several stages of the production process (e.g., saccharification) can offer a sustainable route due to avoidance of harsh chemicals and high temperatures. For novel enzyme discovery, physically linked gene clusters targeting carbohydrate degradation in bacteria, polysaccharide utilization loci (PULs), are recognized ‘treasure troves’ in the era of exponentially growing numbers of sequenced genomes. 

Results: We determined the biochemical properties and structure of a protein of unknown function (PUF) encoded within PULs of metagenomes from beaver droppings and moose rumen enriched on poplar hydrolysate. The corresponding novel bifunctional carbohydrate esterase (CE), now named BD-FAE, displayed feruloyl esterase (FAE) and acetyl esterase activity on simple, synthetic substrates. Whereas acetyl xylan esterase (AcXE) activity was detected on acetylated glucuronoxylan from birchwood, only FAE activity was observed on acetylated and feruloylated xylooligosaccharides from corn fiber. The genomic contexts of 200 homologs of BD-FAE revealed that the 33 closest homologs appear in PULs likely involved in xylan breakdown, while the more distant homologs were found either in alginate-targeting PULs or else outside PUL contexts. Although the BD-FAE structure adopts a typical α/β-hydrolase fold with a catalytic triad (Ser-Asp-His), it is distinct from other biochemically characterized CEs. 

Conclusions: The bifunctional CE, BD-FAE, represents a new candidate for biomass processing given its capacity to remove ferulic acid and acetic acid from natural corn and birchwood xylan substrates, respectively. Its detailed biochemical characterization and solved crystal structure add to the toolbox of enzymes for biomass valorization as well as structural information to inform the classification of new CEs.

Original languageEnglish
Article number127
Number of pages16
JournalBiotechnology for Biofuels
Issue number1
Early online date31 May 2021
Publication statusPublished - 31 May 2021
MoE publication typeA1 Journal article-refereed


  • Acetyl xylan esterase (AcXE)
  • Carbohydrate active enzymes (CAZymes)
  • Carbohydrate esterase (CE)
  • Enzyme discovery
  • Feruloyl esterase (FAE)
  • Polysaccharide utilization loci (PULs)
  • Protein of unknown function (PUF)
  • Xylan


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