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Fungi isolated from Miscanthus and sugarcane: biomass conversion, fungal enzymes, and hydrolysis of plant cell wall polymers.

Shrestha P, Ibáñez AB, Bauer S, Glassman SI, Szaro TM, Bruns TD, Taylor JW - Biotechnol Biofuels (2015)

Bottom Line: To make a meaningful reduction in fossil fuel use, bioethanol must be produced from the entire plant rather than only its starch or sugars.Here, we thoroughly analyze 30 of these fungi including those most often found on decaying leaves and stems of these plants, as well as four fungi chosen because they are well-studied for their plant cell wall deconstructing enzymes, for wood decay, or for genetic regulation of plant cell wall deconstruction.We extend our analysis to assess not only their ability over an 8-week period to bioconvert Miscanthus cell walls but also their ability to secrete total protein, to secrete enzymes with the activities of xylanases, exocellulases, endocellulases, and beta-glucosidases, and to remove specific parts of Miscanthus cell walls, that is, glucan, xylan, arabinan, and lignin.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102 USA.

ABSTRACT

Background: Biofuel use is one of many means of addressing global change caused by anthropogenic release of fossil fuel carbon dioxide into Earth's atmosphere. To make a meaningful reduction in fossil fuel use, bioethanol must be produced from the entire plant rather than only its starch or sugars. Enzymes produced by fungi constitute a significant percentage of the cost of bioethanol production from non-starch (i.e., lignocellulosic) components of energy crops and agricultural residues. We, and others, have reasoned that fungi that naturally deconstruct plant walls may provide the best enzymes for bioconversion of energy crops.

Results: Previously, we have reported on the isolation of 106 fungi from decaying leaves of Miscanthus and sugarcane (Appl Environ Microbiol 77:5490-504, 2011). Here, we thoroughly analyze 30 of these fungi including those most often found on decaying leaves and stems of these plants, as well as four fungi chosen because they are well-studied for their plant cell wall deconstructing enzymes, for wood decay, or for genetic regulation of plant cell wall deconstruction. We extend our analysis to assess not only their ability over an 8-week period to bioconvert Miscanthus cell walls but also their ability to secrete total protein, to secrete enzymes with the activities of xylanases, exocellulases, endocellulases, and beta-glucosidases, and to remove specific parts of Miscanthus cell walls, that is, glucan, xylan, arabinan, and lignin.

Conclusion: This study of fungi that bioconvert energy crops is significant because 30 fungi were studied, because the fungi were isolated from decaying energy grasses, because enzyme activity and removal of plant cell wall components were recorded in addition to biomass conversion, and because the study period was 2 months. Each of these factors make our study the most thorough to date, and we discovered fungi that are significantly superior on all counts to the most widely used, industrial bioconversion fungus, Trichoderma reesei. Many of the best fungi that we found are in taxonomic groups that have not been exploited for industrial bioconversion and the cultures are available from the Centraalbureau voor Schimmelcultures in Utrecht, Netherlands, for all to use.

No MeSH data available.


Related in: MedlinePlus

Heat map(green = low, yellow = intermediate, red = high)of reduction ofMiscanthuscell wall components by fungal bioconversion ofMiscanthusover 8 weeks of solid substrate fermentation. GenBank accession numbers are given for fungi isolated by us from Miscanthus or sugarcane.
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Fig4: Heat map(green = low, yellow = intermediate, red = high)of reduction ofMiscanthuscell wall components by fungal bioconversion ofMiscanthusover 8 weeks of solid substrate fermentation. GenBank accession numbers are given for fungi isolated by us from Miscanthus or sugarcane.

Mentions: Removal of glucan, a broad category that represents cellulose, was topped by P. chrysosporium at 23.3% followed by five other species with more than 18% removal, including Chloridium sp1 at 19.9%, N. crassa at 18.1%, and three Dothideomycetes. The two other positive control fungal species, T. reesei QM9414 and P. placenta were able to consume 11.5% and 14.1% glucan by week 8 (Figure 4).Figure 4


Fungi isolated from Miscanthus and sugarcane: biomass conversion, fungal enzymes, and hydrolysis of plant cell wall polymers.

Shrestha P, Ibáñez AB, Bauer S, Glassman SI, Szaro TM, Bruns TD, Taylor JW - Biotechnol Biofuels (2015)

Heat map(green = low, yellow = intermediate, red = high)of reduction ofMiscanthuscell wall components by fungal bioconversion ofMiscanthusover 8 weeks of solid substrate fermentation. GenBank accession numbers are given for fungi isolated by us from Miscanthus or sugarcane.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4362644&req=5

Fig4: Heat map(green = low, yellow = intermediate, red = high)of reduction ofMiscanthuscell wall components by fungal bioconversion ofMiscanthusover 8 weeks of solid substrate fermentation. GenBank accession numbers are given for fungi isolated by us from Miscanthus or sugarcane.
Mentions: Removal of glucan, a broad category that represents cellulose, was topped by P. chrysosporium at 23.3% followed by five other species with more than 18% removal, including Chloridium sp1 at 19.9%, N. crassa at 18.1%, and three Dothideomycetes. The two other positive control fungal species, T. reesei QM9414 and P. placenta were able to consume 11.5% and 14.1% glucan by week 8 (Figure 4).Figure 4

Bottom Line: To make a meaningful reduction in fossil fuel use, bioethanol must be produced from the entire plant rather than only its starch or sugars.Here, we thoroughly analyze 30 of these fungi including those most often found on decaying leaves and stems of these plants, as well as four fungi chosen because they are well-studied for their plant cell wall deconstructing enzymes, for wood decay, or for genetic regulation of plant cell wall deconstruction.We extend our analysis to assess not only their ability over an 8-week period to bioconvert Miscanthus cell walls but also their ability to secrete total protein, to secrete enzymes with the activities of xylanases, exocellulases, endocellulases, and beta-glucosidases, and to remove specific parts of Miscanthus cell walls, that is, glucan, xylan, arabinan, and lignin.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102 USA.

ABSTRACT

Background: Biofuel use is one of many means of addressing global change caused by anthropogenic release of fossil fuel carbon dioxide into Earth's atmosphere. To make a meaningful reduction in fossil fuel use, bioethanol must be produced from the entire plant rather than only its starch or sugars. Enzymes produced by fungi constitute a significant percentage of the cost of bioethanol production from non-starch (i.e., lignocellulosic) components of energy crops and agricultural residues. We, and others, have reasoned that fungi that naturally deconstruct plant walls may provide the best enzymes for bioconversion of energy crops.

Results: Previously, we have reported on the isolation of 106 fungi from decaying leaves of Miscanthus and sugarcane (Appl Environ Microbiol 77:5490-504, 2011). Here, we thoroughly analyze 30 of these fungi including those most often found on decaying leaves and stems of these plants, as well as four fungi chosen because they are well-studied for their plant cell wall deconstructing enzymes, for wood decay, or for genetic regulation of plant cell wall deconstruction. We extend our analysis to assess not only their ability over an 8-week period to bioconvert Miscanthus cell walls but also their ability to secrete total protein, to secrete enzymes with the activities of xylanases, exocellulases, endocellulases, and beta-glucosidases, and to remove specific parts of Miscanthus cell walls, that is, glucan, xylan, arabinan, and lignin.

Conclusion: This study of fungi that bioconvert energy crops is significant because 30 fungi were studied, because the fungi were isolated from decaying energy grasses, because enzyme activity and removal of plant cell wall components were recorded in addition to biomass conversion, and because the study period was 2 months. Each of these factors make our study the most thorough to date, and we discovered fungi that are significantly superior on all counts to the most widely used, industrial bioconversion fungus, Trichoderma reesei. Many of the best fungi that we found are in taxonomic groups that have not been exploited for industrial bioconversion and the cultures are available from the Centraalbureau voor Schimmelcultures in Utrecht, Netherlands, for all to use.

No MeSH data available.


Related in: MedlinePlus