Abstract
Background: Agave species can grow well in semi-arid marginal agricultural lands around the world. Selected Agave species are used largely for alcoholic beverage production in Mexico. There are expanding research efforts to use the plentiful residues (bagasse) for ethanol production as the beverage manufacturing process only uses the juice from the central core of mature plants. Here, we investigate the potential of over a dozen Agave species, including three from cold semi-arid regions of the United States, to produce biofuels using the whole plant. Results: Ethanol was readily produced by Saccharomyces cerevisiae from hydrolysate of ten whole Agaves with the use of a proper blend of biomass degrading enzymes including inulinase that overcomes inhibition of most of the species tested. As an example, US grown Agave neomexicana produced 119 ± 11 mg ethanol/g biomass. Unlike yeast fermentations, Clostridium beijerinckii produced n-butanol plus acetone from all species tested. Butyric acid, a precursor of n-butanol, was also present due to incomplete conversion during the screening process. Since Agave contains high levels of free and polyfructose which are readily destroyed by acidic pretreatment, a two-step procedure was developed to depolymerize polyfructose while maintaining its fermentability. The hydrolysate from before and after dilute acid processing was used in C. beijerinckii fermentations with selected Agave species with A. neomexicana producing 144 ± 4 mg fermentation products/g biomass. Conclusions: Results showed Agave's potential to be a source of fermentable sugars beyond the existing beverage species to now include many species previously unfermentable by yeast, including cold-tolerant lines. This development should stimulate development of Agave as a dedicated feedstock for biofuels in semi-arid regions throughout the globe.
| Original language | English |
|---|---|
| Article number | 79 |
| Journal | Biotechnology for Biofuels |
| Volume | 8 |
| Issue number | 1 |
| DOIs | |
| State | Published - May 30 2015 |
Funding
The authors would like to thank Novozymes, and Genencor International for providing some of the enzymes gratis. The authors thank Jim Notestein (Southerngardening.org) for assisting in acquiring the majority of the Agave plants. The authors thank Prof. Neal Stewart, Dept. Plant Sciences, Univ. Tennessee, for facilitating the repeat of selected experiments by the corresponding author at Oak Ridge National Laboratory after his retirement from the lab. Funding was provided by Oak Ridge National Laboratory Directed Research and Development (LDRD) for support of most of this research. A portion of this research was funded by the BioEnergy Science Center (BESC) which is a US Department of Energy BioEnergy Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science. This manuscript has been authored by a contractor of the US Government under contract DE-AC05-00OR22725. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
| Funders | Funder number |
|---|---|
| BioEnergy Science Center | |
| Oak Ridge National Laboratory | |
| U.S. Department of Energy | |
| Office of Science | DE-AC05-00OR22725 |
| Biological and Environmental Research | |
| Laboratory Directed Research and Development |
Keywords
- Butyric acid
- Clostridium beijerinckii
- Dedicated feedstock
- Ethanol
- Fermentation
- Inulinase
- Poly-fructose
- Semi-arid
- n-Butanol
