Discovery and applications of family AA9 lytic polysaccharide monooxygenases
Doktorsavhandling, 2023

Auxililary activity family 9 lytic polysaccharide monooxygenases (abbreviated as AA9s or LPMO9s) are fungal mono-copper enzymes capable of oxidatively cleaving various plant cell wall oligo- and/or polysaccharides. LPMO9s are key components of lignocellulolytic enzyme cocktails used in today’s biorefineries to break down biomass into fermentable sugars.
Highly stable enzymes with novel functions are of great interest to improve enzymatic biorefinery processes and their economic feasibility. Genome sequencing of an industrially relevant fungus, Thermothielavioides terrestris LPH172, revealed 411 putative carbohydrate-active enzyme (CAZy) domains. Transcriptomic analysis indicated that the fungus upregulated numerous LPMO9 genes in concert with canonical cellulase and hemicellulase encoding genes to degrade lignocellulose. Nuanced co-upregulation was detected for LPMO9 genes and those encoding other redox-active CAZymes. Six strongly upregulated TtLPMO9 genes were heterologously expressed and functionally characterized using cellulosic and hemicellulosic substrates. These studies showed that the multitude of LPMO9 genes provided the fungus with different functions, including previously unknown cleavage of cellulose-associated spruce arabinoglucuronoxylan and acetylated birch glucuronoxylan. In a related study, xylanolytic LPMO9 activity was revealed or enhanced by debranching xylans enzymatically, which likely assumed a rigid and stretched xylan conformation that associated with cellulose to increase accessibility to LPMO9s.
LPMOs have unique oxidative powers which render them advantageous for various biorefinery applications. A C1-oxidizing TtLPMO9G was found to increase the amount of carboxyl groups on sulfated cellulose nanocrystals by 10%, without any extensive degradation of the crystals. The functional groups thus generated were used for proof-of-concept crosslinking, which could aid in the production of bio-based materials. In another application, addition of TaLPMO9A to a benchmark LPMO-poor cellulolytic cocktail was shown to improve saccharification yields of mildly pretreated spruce substrates. The final glucose and xylose yields were increased by up to 1.6- and 1.5-fold, respectively, illustrating how LPMO9s can be exploited in the saccharification of these notoriously recalcitrant substrates.

lytic polysaccharide monooxygenases

cellulose

xylan

spruce

carbohydrate active enzymes

LPMO

lignocellulolytic enzyme cocktails

lignocellulose

polysaccharides

AA9

cellulose nanocrystals

thermophilic fungi

FB-salen, Fysikgården 4
Opponent: Maija Tenkanen, Helsiniki University, Finland

Författare

Monika Tõlgo

Chalmers, Life sciences, Industriell bioteknik

Enzymatic debranching is a key determinant of the xylan-degrading activity of family AA9 lytic polysaccharide monooxygenases

Biotechnology for Biofuels and Bioproducts,;Vol. 16(2023)

Artikel i vetenskaplig tidskrift

Investigating the role of AA9 LPMOs in enzymatic hydrolysis of differentially steam-pretreated spruce

Biotechnology for Biofuels and Bioproducts,;Vol. 16(2023)

Artikel i vetenskaplig tidskrift

Navarro Llacer, S., Tõlgo, M., Olsson, L., & Nypelö, T. Carboxylation of sulfated cellulose nanocrystals by family AA9 lytic polysaccharide monooxygenases.

Discovery and applications of novel enzymes for wood-based biorefineries

To produce biofuels and biochemicals via fermentation, polysaccharides present in biomass must be first degraded into their constituent sugar units. This process is called saccharification and is achieved by enzymes, which are expensive bioreagents and therefore require optimization. Lytic polysaccharide monooxygenases (LPMOs) are enzymes that play a crucial role in saccharification. LPMOs are unique compared to other saccharifying enzymes as they use a different, oxidative mechanism. I have studied a specific type of LPMOs (AA9s), mainly from the fungus T. terrestris LPH172. I show that besides cellulose, some of these AA9s are highly active on xylan, another important component of wood biomass. In fact, my thesis describes how to increase AA9 activity on xylan even further. These findings will help to lower the cost of saccharification and broaden the range of usable LPMO substrates.

AA9s, supplied as part of enzyme cocktails, are currently being used in biorefineries to degrade biomass. I showed that one type of AA9 could increase, by up to 1.6-fold, the saccharification yields of mildly pretreated spruce, a notoriously hard-to-degrade but widely available biomass in Sweden. Separately, I showed that another AA9 could modify cellulose instead of degrading it. This is important as it allows the addition of new functions to sulfated nanocellulose and, hence, the production of novel and sustainable bio-based materials.

Enzymer upptäckt och produktion i Vietnam för produktion av hållbara biobränslen och biokemikalier

Vetenskapsrådet (VR) (2014-3523), 2014-12-01 -- 2016-12-31.

Drivkrafter

Hållbar utveckling

Ämneskategorier

Övrig annan teknik

Biokatalys och enzymteknik

Infrastruktur

Beräkningsinfrastruktur för systembiologi

Infrastruktur för kemisk avbildning

Fundament

Grundläggande vetenskaper

Styrkeområden

Materialvetenskap

ISBN

978-91-7905-751-0

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5217

Utgivare

Chalmers

FB-salen, Fysikgården 4

Online

Opponent: Maija Tenkanen, Helsiniki University, Finland

Mer information

Senast uppdaterat

2023-05-05