title: Enhancing alfalfa conversion efficiencies for sugar recovery and ethanol production by altering lignin composition.
abstract: Alfalfa (Medicago sativa L.) biomass was evaluated for biochemical conversion into ethanol using dilute-acid and ammonia pretreatments. The two alfalfa lines compared were a reduced S-lignin transgenic cultivar generated through down regulation of the caffeic acid O-methyltransferase gene and a wild-type control. Both were harvested at two maturities. All the samples had similar carbohydrate contents including a mean composition of 316 g glucan and 497 g total neutral carbohydrates per kg dry biomass, which corresponds to a theoretic ethanol yield of 382 l/ton. Ethanol yields for alfalfa stems pretreated with dilute-acid were significantly impacted by harvest maturity and lignin composition, whereas when pretreated with dilute-ammonia, yield was solely affected by lignin composition. Use of a recombinant xylose-fermenting Saccharomyces strain, for converting the ammonia pretreated alfalfa samples, further increased ethanol yields. Ethanol yields for the xylose-fermenting yeast were 232-278 l/ton and were significantly enhanced for the reduced S lignin cultivars.
authors.affiliation: Bioenergy Research Unit, United States Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, Peoria, IL 61604, USA. Bruce.Dien@ars.usda.gov
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Dien
authors.forename: David J
authors.initials: DJ
authors.lastname: Miller
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Hector
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dixon
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.forename: Mark
authors.initials: M
authors.lastname: McCaslin
authors.forename: Peter
authors.initials: P
authors.lastname: Reisen
authors.forename: Gautam
authors.initials: G
authors.lastname: Sarath
authors.forename: Michael A
authors.initials: MA
authors.lastname: Cotta
mesh_terms: D000641:Ammonia / Q000494:pharmacology; D018533:Biomass; D002241:Carbohydrates / Q000032:analysis*; D000431:Ethanol / Q000138:chemical synthesis*; D005285:Fermentation / Q000187:drug effects; D008031:Lignin / Q000737:chemistry*; D000455:Medicago sativa / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D008780:Methyltransferases / Q000235:genetics; D010641:Phenotype; D018547:Plant Stems / Q000737:chemistry / Q000187:drug effects; D013464:Sulfuric Acids / Q000494:pharmacology
chemical_list: D002241:Carbohydrates; D013464:Sulfuric Acids; D000431:Ethanol; D000641:Ammonia; D008031:Lignin; D008780:Methyltransferases; C019608:caffeate O-methyltransferase; C033158:sulfuric acid