title: Prospecting for Energy-Rich Renewable Raw Materials: Sorghum Stem Case Study.
abstract: Sorghum vegetative tissues are becoming increasingly important for biofuel production. The composition of sorghum stem tissues is influenced by genotype, environment and photoperiod sensitivity, and varies widely between varieties and also between different stem tissues (outer rind vs inner pith). Here, the amount of cellulose, (1,3;1,4)-β-glucan, arabinose and xylose in the stems of twelve diverse sorghum varieties, including four photoperiod-sensitive varieties, was measured. At maturity, most photoperiod-insensitive lines had 1% w/w (1,3;1,4)-β-glucan in stem pith tissue whilst photoperiod-sensitive varieties remained in a vegetative stage and accumulated up to 6% w/w (1,3;1,4)-β-glucan in the same tissue. Three sorghum lines were chosen for further study: a cultivated grain variety (Sorghum bicolor BTx623), a sweet variety (S. bicolor Rio) and a photoperiod-sensitive wild line (S. bicolor ssp. verticilliflorum Arun). The Arun line accumulated 5.5% w/w (1,3;1,4)-β-glucan and had higher SbCslF6 and SbCslH3 transcript levels in pith tissues than did photoperiod-insensitive varieties Rio and BTx623 (<1% w/w pith (1,3;1,4)-β-glucan). To assess the digestibility of the three varieties, stem tissue was treated with either hydrolytic enzymes or dilute acid and the release of fermentable glucose was determined. Despite having the highest lignin content, Arun yielded significantly more glucose than the other varieties, and theoretical calculation of ethanol yields was 10 344 L ha-1 from this sorghum stem tissue. These data indicate that sorghum stem (1,3;1,4)-β-glucan content may have a significant effect on digestibility and bioethanol yields. This information opens new avenues of research to generate sorghum lines optimised for biofuel production.
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Caitlin S
authors.identifier: http://orcid.org/0000-0001-8549-2873
authors.initials: CS
authors.lastname: Byrt
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Natalie S
authors.initials: NS
authors.lastname: Betts
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Hwei-Ting
authors.initials: HT
authors.lastname: Tan
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Wai Li
authors.initials: WL
authors.lastname: Lim
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Riksfardini A
authors.initials: RA
authors.lastname: Ermawar
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Hai Yen
authors.initials: HY
authors.lastname: Nguyen
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Shirley
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Jelle
authors.initials: J
authors.lastname: Lahnstein
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Kendall
authors.initials: K
authors.lastname: Corbin
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Fincher
authors.affiliation: Arcadia Biosciences, Davis, CA, United States of America.
authors.forename: Vic
authors.initials: V
authors.lastname: Knauf
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Burton
mesh_terms: D056804:Biofuels; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D000431:Ethanol / Q000737:chemistry; D005838:Genotype; D005947:Glucose / Q000378:metabolism; D018547:Plant Stems / Q000166:cytology / Q000378:metabolism*; D045868:Sorghum / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D013213:Starch / Q000378:metabolism
chemical_list: D056804:Biofuels; D000431:Ethanol; D002244:Carbon; D013213:Starch; D005947:Glucose