Wood is a major pool of organic carbon that is highly resistant to decay, owing largely to the presence of lignin. The only organisms capable of substantial lignin decay are white rot fungi in the Agaricomycetes, which also contains non-lignin-degrading brown rot and ectomycorrhizal species. Comparative analyses of 31 fungal genomes (12 generated for this study) suggest that lignin-degrading peroxidases expanded in the lineage leading to the ancestor of the Agaricomycetes, which is reconstructed as a white rot species, and then contracted in parallel lineages leading to brown rot and mycorrhizal species. Molecular clock analyses suggest that the origin of lignin degradation might have coincided with the sharp decrease in the rate of organic carbon burial around the end of the Carboniferous period.

/pdf/the-paleozoic-origin-of-enzymatic-lignin-decomposition-4stwcdzzgi.pdf

The paleozoic origin of enzymatic lignin decomposition reconstructed from 31 fungal genomes

Efficient enzymatic conversion of crystalline polysaccharides is crucial for an economically and environmentally sustainable bioeconomy but remains unfavorably inefficient. We describe an enzyme that acts on the surface of crystalline chitin, where it introduces chain breaks and generates oxidized chain ends, thus promoting further degradation by chitinases. This enzymatic activity was discovered and further characterized by using mass spectrometry and chromatographic separation methods to detect oxidized products generated in the absence or presence of H 2 18 O or 18 O 2 . There are strong indications that similar enzymes exist that work on cellulose. Our findings not only demonstrate the existence of a hitherto unknown enzyme activity but also provide new avenues toward more efficient enzymatic conversion of biomass.

https://science.sciencemag.org/content/sci/330/6001/219.full.pdf

An oxidative enzyme boosting the enzymatic conversion of recalcitrant polysaccharides.

Since its inception, the carbohydrate-active enzymes database (CAZy; http://www.cazy.org
 ) has described the families of enzymes that cleave or build complex carbohydrates, namely the glycoside hydrolases (GH), the polysaccharide lyases (PL), the carbohydrate esterases (CE), the glycosyltransferases (GT) and their appended non-catalytic carbohydrate-binding modules (CBM). The recent discovery that members of families CBM33 and family GH61 are in fact lytic polysaccharide monooxygenases (LPMO), demands a reclassification of these families into a suitable category. Because lignin is invariably found together with polysaccharides in the plant cell wall and because lignin fragments are likely to act in concert with (LPMO), we have decided to join the families of lignin degradation enzymes to the LPMO families and launch a new CAZy class that we name “Auxiliary Activities” in order to accommodate a range of enzyme mechanisms and substrates related to lignocellulose conversion. Comparative analyses of these auxiliary activities in 41 fungal genomes reveal a pertinent division of several fungal groups and subgroups combining their phylogenetic origin and their nutritional mode (white vs. brown rot). The new class introduced in the CAZy database extends the traditional CAZy families, and provides a better coverage of the full extent of the lignocellulose breakdown machinery.

/pdf/expansion-of-the-enzymatic-repertoire-of-the-cazy-database-23c38ut1lr.pdf

Expansion of the enzymatic repertoire of the CAZy database to integrate auxiliary redox enzymes

The bulk terrestrial biomass resource in a future bio-economy will be lignocellulosic biomass, which is recalcitrant and challenging to process. Enzymatic conversion of polysaccharides in the lignocellulosic biomass will be a key technology in future biorefineries and this technology is currently the subject of intensive research. We describe recent developments in enzyme technology for conversion of cellulose, the most abundant, homogeneous and recalcitrant polysaccharide in lignocellulosic biomass. In particular, we focus on a recently discovered new type of enzymes currently classified as CBM33 and GH61 that catalyze oxidative cleavage of polysaccharides. These enzymes promote the efficiency of classical hydrolytic enzymes (cellulases) by acting on the surfaces of the insoluble substrate, where they introduce chain breaks in the polysaccharide chains, without the need of first “extracting” these chains from their crystalline matrix.

/pdf/novel-enzymes-for-the-degradation-of-cellulose-2iq204k1s3.pdf

Novel enzymes for the degradation of cellulose

The enzymatic degradation of recalcitrant plant biomass is one of the key industrial challenges of the 21st century. Accordingly, there is a continuing drive to discover new routes to promote polysaccharide degradation. Perhaps the most promising approach involves the application of “cellulase-enhancing factors,” such as those from the glycoside hydrolase (CAZy) GH61 family. Here we show that GH61 enzymes are a unique family of copper-dependent oxidases. We demonstrate that copper is needed for GH61 maximal activity and that the formation of cellodextrin and oxidized cellodextrin products by GH61 is enhanced in the presence of small molecule redox-active cofactors such as ascorbate and gallate. By using electron paramagnetic resonance spectroscopy and single-crystal X-ray diffraction, the active site of GH61 is revealed to contain a type II copper and, uniquely, a methylated histidine in the copper's coordination sphere, thus providing an innovative paradigm in bioinorganic enzymatic catalysis.

https://www.pnas.org/content/pnas/108/37/15079.full.pdf

Insights into the oxidative degradation of cellulose by a copper metalloenzyme that exploits biomass components

Currently, the relatively high cost of enzymes such as glycoside hydrolases that catalyze cellulose hydrolysis represents a barrier to commercialization of a biorefinery capable of producing renewable transportable fuels such as ethanol from abundant lignocellulosic biomass. Among the many families of glycoside hydrolases that catalyze cellulose and hemicellulose hydrolysis, few are more enigmatic than family 61 (GH61), originally classified based on measurement of very weak endo-1,4-beta-d-glucanase activity in one family member. Here we show that certain GH61 proteins lack measurable hydrolytic activity by themselves but in the presence of various divalent metal ions can significantly reduce the total protein loading required to hydrolyze lignocellulosic biomass. We also solved the structure of one highly active GH61 protein and find that it is devoid of conserved, closely juxtaposed acidic side chains that could serve as general proton donor and nucleophile/base in a canonical hydrolytic reaction, and we conclude that the GH61 proteins are unlikely to be glycoside hydrolases. Structure-based mutagenesis shows the importance of several conserved residues for GH61 function. By incorporating the gene for one GH61 protein into a commercial Trichoderma reesei strain producing high levels of cellulolytic enzymes, we are able to reduce by 2-fold the total protein loading (and hence the cost) required to hydrolyze lignocellulosic biomass.

Stimulation of lignocellulosic biomass hydrolysis by proteins of glycoside hydrolase family 61: structure and function of a large, enigmatic family

The present invention relates to methods for producing a polypeptide, comprising: (a) cultivating a fungal host cell in a medium conducive for the production of the polypeptide, wherein the fungal host cell comprises a first nucleic acid sequence encoding the polypeptide operably linked to a second nucleic acid sequence comprising a promoter foreign to the nucleic acid sequence, wherein the promoter comprises a sequence selected from the group consisting of nucleotides 1 to 3949 of SEQ ID NO. 1, nucleotides 1 to 938 of SEQ ID NO. 2, and nucleotides 1 to 3060 of SEQ ID NO. 3, and a subsequence thereof; and mutant, hybrid, and tandem promoters thereof; and (b) isolating the polypeptide from the cultivation medium. The present invention also relates to the isolated promoter sequences and to constructs, vectors, and fungal host cells comprising the promoter sequences operably linked to nucleic acid sequences encoding polypeptides.

Promoters for expressing genes in a fungal cell

The present invention relates to isolated polypeptides having cellulolytic enhancing activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.

Polypeptides having cellulolytic enhancing activity and polynucleotides encoding same

The present invention relates to isolated polypeptides having feruloyl esterase activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.

Polypeptides having feruloyl esterase activity and polynucleotides encoding same

The present invention relates to isolated polypeptides having alpha-L-arabinofuranosidase activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.

Kimberly Brown

Papers

Stimulation of lignocellulosic biomass hydrolysis by proteins of glycoside hydrolase family 61: structure and function of a large, enigmatic family

Promoters for expressing genes in a fungal cell

Polypeptides having cellulolytic enhancing activity and polynucleotides encoding same

Polypeptides having feruloyl esterase activity and polynucleotides encoding same

Polypeptides having arabinofuranosidase activity and polynucleotides encoding same