Multimodular fused acetyl–feruloyl esterases from soil and gut Bacteroidetes improve xylanase depolymerization of recalcitrant biomass
Journal article, 2020

Background
Plant biomass is an abundant and renewable carbon source that is recalcitrant towards both chemical and biochemical degradation. Xylan is the second most abundant polysaccharide in biomass after cellulose, and it possesses a variety of carbohydrate substitutions and non-carbohydrate decorations which can impede enzymatic degradation by glycoside hydrolases. Carbohydrate esterases are able to cleave the ester-linked decorations and thereby improve the accessibility of the xylan backbone to glycoside hydrolases, thus improving the degradation process. Enzymes comprising multiple catalytic glycoside hydrolase domains on the same polypeptide have previously been shown to exhibit intramolecular synergism during degradation of biomass. Similarly, natively fused carbohydrate esterase domains are encoded by certain bacteria, but whether these enzymes can result in similar synergistic boosts in biomass degradation has not previously been evaluated.

Results
Two carbohydrate esterases with similar architectures, each comprising two distinct physically linked catalytic domains from families 1 (CE1) and 6 (CE6), were selected from xylan-targeting polysaccharide utilization loci (PULs) encoded by the Bacteroidetes species Bacteroides ovatus and Flavobacterium johnsoniae. The full-length enzymes as well as the individual catalytic domains showed activity on a range of synthetic model substrates, corn cob biomass, and Japanese beechwood biomass, with predominant acetyl esterase activity for the N-terminal CE6 domains and feruloyl esterase activity for the C-terminal CE1 domains. Moreover, several of the enzyme constructs were able to substantially boost the performance of a commercially available xylanase on corn cob biomass (close to twofold) and Japanese beechwood biomass (up to 20-fold). Interestingly, a significant improvement in xylanase biomass degradation was observed following addition of the full-length multidomain enzyme from B. ovatus versus the addition of its two separated single domains, indicating an intramolecular synergy between the esterase domains. Despite high sequence similarities between the esterase domains from B. ovatus and F. johnsoniae, their addition to the xylanolytic reaction led to different degradation patterns.

Conclusion
We demonstrated that multidomain carbohydrate esterases, targeting the non-carbohydrate decorations on different xylan polysaccharides, can considerably facilitate glycoside hydrolase-mediated hydrolysis of xylan and xylan-rich biomass. Moreover, we demonstrated for the first time a synergistic effect between the two fused catalytic domains of a multidomain carbohydrate esterase.

Polysaccharide utilization locus

Acetyl xylan esterase

Carbohydrate esterase

Carbohydrate-active enzyme

Corn cob

Beech wood

Feruloyl esterase

Multidomain enzymes

Xylan

Author

Cathleen Kmezik

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Cyrielle Bonzom

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Lisbeth Olsson

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Scott Mazurkewich

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Johan Larsbrink

Chalmers, Biology and Biological Engineering, Industrial Biotechnology

Biotechnology for Biofuels

1754-6834 (eISSN)

Vol. 13 1 60

Development of a consolidated bioprocess for conversion of plant biomass to versatile chemical building blocks

Novo Nordisk Fonden, 2018-01-01 -- 2020-12-31.

Swedish Research Council (VR), 2017-01-01 -- 2020-12-31.

ÅForsk, 2017-07-01 -- 2018-05-31.

Enzymes for selective decomposition of woody biomass

Knut and Alice Wallenberg Foundation, 2014-01-01 -- 2018-12-31.

Driving Forces

Sustainable development

Subject Categories

Biochemistry and Molecular Biology

Microbiology

Agricultural Biotechnology

Areas of Advance

Energy

Health Engineering

Life Science Engineering (2010-2018)

Roots

Basic sciences

DOI

10.1186/s13068-020-01698-9

More information

Latest update

5/20/2020