Hydrolytic Methods for the Quantification of Fructose Equivalents in Herbaceous Biomass

Abstract

A low, but significant, fraction of the carbohydrate portion of herbaceous biomass may be composed of fructose/fructosyl-containing components ("fructose equivalents"); such carbohydrates include sucrose, fructooligosaccharides, and fructans. Standard methods used for the quantification of structural-carbohydrate-derived neutral monosaccharide equivalents in biomass are not particularly well suited for the quantification of fructose equivalents due to the inherent instability of fructose in conditions commonly used for hemicellulose/cellulose hydrolysis (>80% degradation of fructose standards treated at 4% sulfuric acid, 121 degrees C, 1 h). Alternative time, temperature, and acid concentration combinations for fructan hydrolysis were considered using model fructans (inulin, beta-2,1, and levan, beta-2,6) and a grass seed straw (tall fescue, Festuca arundinacea) as representative feedstocks. The instability of fructose, relative to glucose and xylose, at higher acid/temperature combinations is demonstrated, all rates of fructose degradation being acid and temperature dependent. Fructans are shown to be completely hydrolyzed at acid concentrations well below that used for the structural carbohydrates, as low as 0.2%, at 121 degrees C for 1 h. Lower temperatures are also shown to be effective, with corresponding adjustments in acid concentration and time. Thus, fructans can be effectively hydrolyzed under conditions where fructose degradation is maintained below 10%. Hydrolysis of the beta-2,1 fructans at temperatures > or =50 degrees C, at all conditions consistent with complete hydrolysis, appears to generate difructose dianhydrides. These same compounds were not detected upon hydrolysis of levan, sucrose, or straw components. It is suggested that fructan hydrolysis conditions be chosen such that hydrolysis goes to completion; fructose degradation is minimized, and difructose dianhydride production is accounted for.

Laticifer-Specific cis-Prenyltransferase Silencing Affects the Rubber, Triterpene, and Inulin Content of Taraxacum brevicorniculatum

“…We used an independent method based on the enzymatic hydrolysis of root extracts and the photometric quantitation of Fru and Glc to confirm the inulin levels in the four lines. The absolute values obtained by this method were considerably lower than those determined by 1 H-NMR (Supplemental Table S1), but this may reflect the partial degradation of Fru under the experimental conditions used for inulin hydrolysis resulting in the underestimation of inulin levels (Szambelan and Nowak, 2006;Nasab et al, 2009;Nguyen et al, 2009). Therefore, we normalized the amounts of inulin to relative values, setting the wildtype level arbitrarily to 100 (Table IV).…”

One-pot conversion of cellobiose to mannose using a hybrid phosphotungstic acid–cerium oxide catalyst

“…Many of these sugars are valuable on their own and they have the potential to be converted into other high value products. 11 The enzymatic production of mannose from glucose, a major building block of non-edible biomass, appears to be much less common. 9,10 Research on the enzymatic production of mannose has been primarily focused on the conversion of fructose to mannose.…”

Sugar yield and composition of tubers from Jerusalem Artichoke (Helianthus tuberosus) irrigated with saline waters

“…First, diluted juices (20‐times in DI water) and soluble sugars were analyzed directly by HPLC for free sucrose, glucose, fructose, and any other mono‐ or dimeric sugars. Second, to break down sugar oligomers into monomers that could be measured via our HPLC, diluted juices (50‐times in DI water) and diluted soluble sugar liquids (10‐time in DI water) were hydrolyzed in 0.5% sulfuric acid at 121 °C for 30 min in an autoclave (Model HA‐300MII, Hirayama Manufacturing Corp., Tokyo, Japan) (Li et al, ; Nguyen, Sophonputtanaphoca, Kim, & Penner, ) followed by centrifuging at 15,000 rpm for 5 min, neutralizing with calcium carbonate to pH 7, and centrifuging again at 15,000 rpm for 5 min, followed by HPLC quantification for total glucose and fructose in the supernatant. Degradation of sugars due to this post hydrolysis at 121 °C was calculated as percentage sugar recovery through inclusion of sugar recovery standards along with unknown samples.…”