Poster

P6.3 – Esterases for extracting suberin-derived fatty acids from tree bark

Meera Christopher

Chalmers University of Technology

Co-author(s):
Meera Christopher, Division of Industrial Biotechnology, Department of Life Sciences, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden; Wallenberg Wood Science Centre, Department of Life Sciences, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
Lisbeth Olsson, Division of Industrial Biotechnology, Department of Life Sciences, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden; Wallenberg Wood Science Centre, Department of Life Sciences, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden

Forestry is a significant industry in Europe; however, this sector generates large quantities (~ 359 million m3 per annum [1]) of bark residues as by-products, which are often burned as waste. Structurally, one of the most abundant components of bark is suberin- a complex lipid-like compound with a high fatty-acid (FA) content (~ 90% w/w) [2]. Since FAs are essential building blocks for various industrial applications, extracting FAs from bark residues offers both economic and environmental advantages.Currently used chemical extraction methods for FAs rely on the use of harsh solvents and energy-intensive processes. In this study, we have focused on developing an enzymatic process for extracting FAs from birch bark, which offers the advantages of specificity and mild operating conditions. The challenges here are that suberin is predominantly composed of long chain fatty acids (LCFAs, carbon chain length ≥12), that are extensively crosslinked with other components of lignocellulose (such as lignin, cellulose and xylans). Even though a few cutinases and suberinases have been previously reported to act on LCFAs, these enzymes had higher activity on short chain substrates [3–6], indicating that they are not specialized for suberin depolymerization.By induced selection from a collection of fungi isolated from niche environments in Vietnam, we have identified a filamentous fungus Talaromyces sp. AS 616-3 (T-616), that secretes esterases with >10-fold higher activity on long chain model substrates, compared to short/medium chain substrates, thereby proving their potential in de-esterifying suberin (Fig. 1). However, hydrolysis of pretreated birch bark using these enzymes did not result in the release of free FAs. FTIR analysis of the residual substrates after hydrolysis revealed evidence of de-esterification (Fig. 2), indicating that further studies on the intramolecular bonding between suberin and other bark polymers are needed to develop an efficient enzyme cocktail for releasing FAs from bark.

 

References:

1.Kwan, I., T. Huang, M. Ek,
R. Seppänen, and P. Skagerlind (2022) Bark from Nordic tree species – A
sustainable source for amphiphilic polymers and surfactants. Nord Pulp Paper
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Frydrych, A. Greenhalgh, P. Stepnowski, F. Vollrath, A.W.T. King, and C.S.
Pereira (2020) The molecular structure and multifunctionality of the cryptic
plant polymer suberin. Mater Today Bio 5.
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Monga, and M.A. Bernards (2016) Physical, chemical and proteomic evidence of
potato suberin degradation by the plant pathogenic bacterium Streptomyces
scabiei. Microbes Environ 31: 427–434.
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Westh, and D. Ribitsch (2022) Structure-function analysis of two closely
related cutinases from Thermobifida cellulosilytica. Biotechnol Bioeng 119:
470–481.
5.Jabloune, R., M. Khalil, I.E. Ben Moussa, A.M. Simao-Beaunoir, S. Lerat,
R. Brzezinski, and C. Beaulieu (2020) Enzymatic Degradation of p-Nitrophenyl
Esters, Polyethylene Terephthalate, Cutin, and Suberin by Sub1, a Suberinase
Encoded by the Plant Pathogen Streptomyces scabies. Microbes Environ
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6.Novy, V., L.V. Carneiro, J.H. Shin, J. Larsbrink, and L. Olsson (2021)
Phylogenetic analysis and in-depth characterization of functionally and
structurally diverse CE5 cutinases. Journal of Biological Chemistry 297.

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