Research
1 Department of Plant and Microbial Biology, University of California, Berkeley 94720-3102, CA, USA
2 Energy Biosciences Institute, University of California, Berkeley 94720, CA, USA
3 Department of Environmental Science Policy and Management, University of California, Berkeley 94720, CA, USA
Biotechnology for Biofuels 2015, 8:38Â
doi:10.1186/s13068-015-0221-3
Published: 5 March 2015
Abstract (provisional)
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
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 2Â 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.