Table 1.
Comparison of potential biofuel feedstocks.
Fig 1.
Flowchart outlining the steps taken to process and analyze Agave leaves.
Fig 2.
Agave processing and moisture content.
Whole leaves were crushed, producing juice and wet bagasse fractions (a). These fractions were dried separately to calculate moisture content. Data is presented as percentage of fresh (wet) starting mass (% w/w). The values shown in gray are used to calculate total moisture content. The distribution of leaf fresh mass (% w/w) in A. americana and A. tequilana (b).
Fig 3.
Different fractions of Agave material.
Two year old A. tequilana plants in Australia (a). Partially dried leaves reduced to smaller particle sizes using a ball mill (b). Juice extracted from leaves using an experimental shredder (c). Dried fibers after extraction from wet bagasse (d).
Fig 4.
Transverse section of A. tequilana leaf stained with toluidine blue (a). Crystals are situated at the junction between some parenchyma cells within the tissue and at the site of stomata at the epidermis. Vascular bundles and fibers in A. tequilana (b) and A. americana leaf (c) stained with basic fuchsin. Sclerenchymatous fiber cap (sfc); bundle sheath (bs); parenchyma cells (pc); guard cells (gc); cubic shaped crystals (csc); rod shaped crystals (rsc); vascular bundle (vb)
Fig 5.
Agave tissue has pectinaceous crystal clusters localized at cell junctions.
Transmission electron microscopy (TEM) image of crystals between junctions of cells (a) in A. tequilana. Labeling of methyl-esterified homogalacturonan (pectin) with LM20, was identified in the outer sheath of the crystals (b).
Fig 6.
Cell wall polysaccharides detected by immunolabeling and transmission electron microscopy.
Xylem tissue labeled with LM19, an antibody for partially methyl-esterified homogalacturonan (a-b) (pectin, [44]). Parenchyma cells labeled with LM20, an antibody for methyl-esterified homogalacturonans (c-d) [44]. Phloem tissue labeled with LM11 indicating the presence of arabinoxylan [42] (e-f). Leaf inner epidermal cells labeled with an antibody for (1→4)-β-mannan indicating the presence of mannan (g-h) [43]. Scale bars = 1μm.
Table 2.
Composition of A. americana and A. tequilana leaves.
Table 3.
Polysaccharides detected by linkage analysis in Agave leaf.
Fig 7.
Cellulose, the most predominant polymer in Agave leaf tissue is degraded by cellulases.
Liberation of the monomer glucose from the alcohol insoluble residue of A. americana (AA) and A. tequilana (AT) was measured over 48 h. The rate of saccharification is expressed as a percentage of cellulose converted into glucose (n = 3).
Fig 8.
Quantification of juice sugars from A. americana leaves and A. tequilana leaves and stem.
The amount of glucose, fructose and sucrose present in both raw and TFA-treated juice samples (a). Data are presented as g/L. Additional peaks for which there are no known standards were detected in the chromatograms of raw juice (b). A. tequilana stem juice is used as a representative of all three, very similar, chromatograms for the raw and treated samples. Chromatogram of TFA-treated A. tequilana stem juice (c). Chromatogram of fructanase-treated A. tequilana stem juice (d).
Table 4.
Carbohydrates in fiber-enriched fractions from Agave leaves.
Table 5.
Fermentation of Agave tequilana leaf juice using Saccharomyces cerevisiae.
Table 6.
Theoretical ethanol yields for lignocellulosic feedstocks.