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Closely related fungi employ diverse enzymatic strategies to degrade plant biomass.

Benoit I, Culleton H, Zhou M, DiFalco M, Aguilar-Osorio G, Battaglia E, Bouzid O, Brouwer CP, El-Bushari HB, Coutinho PM, Gruben BS, Hildén KS, Houbraken J, Barboza LA, Levasseur A, Majoor E, Mäkelä MR, Narang HM, Trejo-Aguilar B, van den Brink J, vanKuyk PA, Wiebenga A, McKie V, McCleary B, Tsang A, Henrissat B, de Vries RP - Biotechnol Biofuels (2015)

Bottom Line: All tested Aspergilli have a similar genomic potential to degrade plant biomass, with the exception of A. clavatus that has a strongly reduced pectinolytic ability.In addition, significant differences were observed between the enzyme sets produced on these feedstocks, largely correlating with their polysaccharide composition.These data demonstrate that Aspergillus species and possibly also other related fungi employ significantly different approaches to degrade plant biomass.

View Article: PubMed Central - PubMed

Affiliation: Fungal Physiology, CBS-KNAW Fungal Biodiversity Centre and Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands ; Microbiology and Kluyver Centre for Genomics of Industrial Fermentation, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.

ABSTRACT

Background: Plant biomass is the major substrate for the production of biofuels and biochemicals, as well as food, textiles and other products. It is also the major carbon source for many fungi and enzymes of these fungi are essential for the depolymerization of plant polysaccharides in industrial processes. This is a highly complex process that involves a large number of extracellular enzymes as well as non-hydrolytic proteins, whose production in fungi is controlled by a set of transcriptional regulators. Aspergillus species form one of the best studied fungal genera in this field, and several species are used for the production of commercial enzyme cocktails.

Results: It is often assumed that related fungi use similar enzymatic approaches to degrade plant polysaccharides. In this study we have compared the genomic content and the enzymes produced by eight Aspergilli for the degradation of plant biomass. All tested Aspergilli have a similar genomic potential to degrade plant biomass, with the exception of A. clavatus that has a strongly reduced pectinolytic ability. Despite this similar genomic potential their approaches to degrade plant biomass differ markedly in the overall activities as well as the specific enzymes they employ. While many of the genes have orthologs in (nearly) all tested species, only very few of the corresponding enzymes are produced by all species during growth on wheat bran or sugar beet pulp. In addition, significant differences were observed between the enzyme sets produced on these feedstocks, largely correlating with their polysaccharide composition.

Conclusions: These data demonstrate that Aspergillus species and possibly also other related fungi employ significantly different approaches to degrade plant biomass. This makes sense from an ecological perspective where mixed populations of fungi together degrade plant biomass. The results of this study indicate that combining the approaches from different species could result in improved enzyme mixtures for industrial applications, in particular saccharification of plant biomass for biofuel production. Such an approach may result in a much better improvement of saccharification efficiency than adding specific enzymes to the mixture of a single fungus, which is currently the most common approach used in biotechnology.

No MeSH data available.


Growth profiling of eight Aspergilli on plant-biomass related carbon sources. A selection of the growth profile of the eight Aspergillus species on 35 plant biomass related carbon sources is presented. Minimal medium (MM) [1] was used supplemented with 25 mM of mono- or disaccharide, 1% polysaccharide or 3% crude plant biomass. Strains were grown for 5 days after which pictures were taken immediately.
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Fig2: Growth profiling of eight Aspergilli on plant-biomass related carbon sources. A selection of the growth profile of the eight Aspergillus species on 35 plant biomass related carbon sources is presented. Minimal medium (MM) [1] was used supplemented with 25 mM of mono- or disaccharide, 1% polysaccharide or 3% crude plant biomass. Strains were grown for 5 days after which pictures were taken immediately.

Mentions: Growth of the eight Aspergillus species was evaluated on 35 plant biomass related carbon sources (Fig. 2, full profiles are available at www.fung-growth.org). Two isolates per species were tested to check that the differences are species specific and not strain specific. The general growth speed differed between the strains of a species, but for most species no significant carbon source related differences were observed between the strains. An exception to this is A. niger CBS513.88 that grew poorly on all pure carbon sources and was shown to have an amino acid auxotrophy (unpublished data), which explains this phenotype. Apparently, both wheat bran (WB) and sugar beet pulp (SBP) contain sufficient protein/amino acids to supplement this deficiency. All other strains grew well on MM + glucose and glucose was therefore used as an internal reference to compare the strains, to avoid misleading differences caused by general differences in growth speed between the species. Growth on the other substrates relative to growth on glucose was then compared between the species.Fig. 2


Closely related fungi employ diverse enzymatic strategies to degrade plant biomass.

Benoit I, Culleton H, Zhou M, DiFalco M, Aguilar-Osorio G, Battaglia E, Bouzid O, Brouwer CP, El-Bushari HB, Coutinho PM, Gruben BS, Hildén KS, Houbraken J, Barboza LA, Levasseur A, Majoor E, Mäkelä MR, Narang HM, Trejo-Aguilar B, van den Brink J, vanKuyk PA, Wiebenga A, McKie V, McCleary B, Tsang A, Henrissat B, de Vries RP - Biotechnol Biofuels (2015)

Growth profiling of eight Aspergilli on plant-biomass related carbon sources. A selection of the growth profile of the eight Aspergillus species on 35 plant biomass related carbon sources is presented. Minimal medium (MM) [1] was used supplemented with 25 mM of mono- or disaccharide, 1% polysaccharide or 3% crude plant biomass. Strains were grown for 5 days after which pictures were taken immediately.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4522099&req=5

Fig2: Growth profiling of eight Aspergilli on plant-biomass related carbon sources. A selection of the growth profile of the eight Aspergillus species on 35 plant biomass related carbon sources is presented. Minimal medium (MM) [1] was used supplemented with 25 mM of mono- or disaccharide, 1% polysaccharide or 3% crude plant biomass. Strains were grown for 5 days after which pictures were taken immediately.
Mentions: Growth of the eight Aspergillus species was evaluated on 35 plant biomass related carbon sources (Fig. 2, full profiles are available at www.fung-growth.org). Two isolates per species were tested to check that the differences are species specific and not strain specific. The general growth speed differed between the strains of a species, but for most species no significant carbon source related differences were observed between the strains. An exception to this is A. niger CBS513.88 that grew poorly on all pure carbon sources and was shown to have an amino acid auxotrophy (unpublished data), which explains this phenotype. Apparently, both wheat bran (WB) and sugar beet pulp (SBP) contain sufficient protein/amino acids to supplement this deficiency. All other strains grew well on MM + glucose and glucose was therefore used as an internal reference to compare the strains, to avoid misleading differences caused by general differences in growth speed between the species. Growth on the other substrates relative to growth on glucose was then compared between the species.Fig. 2

Bottom Line: All tested Aspergilli have a similar genomic potential to degrade plant biomass, with the exception of A. clavatus that has a strongly reduced pectinolytic ability.In addition, significant differences were observed between the enzyme sets produced on these feedstocks, largely correlating with their polysaccharide composition.These data demonstrate that Aspergillus species and possibly also other related fungi employ significantly different approaches to degrade plant biomass.

View Article: PubMed Central - PubMed

Affiliation: Fungal Physiology, CBS-KNAW Fungal Biodiversity Centre and Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands ; Microbiology and Kluyver Centre for Genomics of Industrial Fermentation, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.

ABSTRACT

Background: Plant biomass is the major substrate for the production of biofuels and biochemicals, as well as food, textiles and other products. It is also the major carbon source for many fungi and enzymes of these fungi are essential for the depolymerization of plant polysaccharides in industrial processes. This is a highly complex process that involves a large number of extracellular enzymes as well as non-hydrolytic proteins, whose production in fungi is controlled by a set of transcriptional regulators. Aspergillus species form one of the best studied fungal genera in this field, and several species are used for the production of commercial enzyme cocktails.

Results: It is often assumed that related fungi use similar enzymatic approaches to degrade plant polysaccharides. In this study we have compared the genomic content and the enzymes produced by eight Aspergilli for the degradation of plant biomass. All tested Aspergilli have a similar genomic potential to degrade plant biomass, with the exception of A. clavatus that has a strongly reduced pectinolytic ability. Despite this similar genomic potential their approaches to degrade plant biomass differ markedly in the overall activities as well as the specific enzymes they employ. While many of the genes have orthologs in (nearly) all tested species, only very few of the corresponding enzymes are produced by all species during growth on wheat bran or sugar beet pulp. In addition, significant differences were observed between the enzyme sets produced on these feedstocks, largely correlating with their polysaccharide composition.

Conclusions: These data demonstrate that Aspergillus species and possibly also other related fungi employ significantly different approaches to degrade plant biomass. This makes sense from an ecological perspective where mixed populations of fungi together degrade plant biomass. The results of this study indicate that combining the approaches from different species could result in improved enzyme mixtures for industrial applications, in particular saccharification of plant biomass for biofuel production. Such an approach may result in a much better improvement of saccharification efficiency than adding specific enzymes to the mixture of a single fungus, which is currently the most common approach used in biotechnology.

No MeSH data available.