Hemicelluloses derivatives

Arabitol testing was performed to ensure that it behaved similarly to xylitol in this reaction to validate xylitol as a model compound. Testing was performed using Ni/Re catalyst from the initial batch screening. Shown in Table 1, the results from the two sugar alcohols were nearly equivalent. This gave some confidence that xylitol should be a valid model compound in the absence of actual hemicellulose derived feedstock. 

Mannose, galactose, and xylose supplementation demonstrated significant inhibition of hydrolysis rate (Fig. 6). Hydrolysis rates decreased by 32, 38, and 45% after supplementation with galactose, xylose, and mannose, respectively, at 100 g/L. The hemicellulose-derived sugars seemed to have a direct inhibitory effect on the cellulase enzymes. The detailed inhibitory mechanisms of these sugars on the cellulase activities were not clear and are currently under investigation. However, it is likely that the mechanisms will depend on both the characteristics of the specific inhibitors and the structure of the different enzymes. 

Fig. 7. Inhibitory effects of supplemented hemicellulose-derived sugars on hydrolysis of 10% acetic acid-pretreated softwood.

Figure 2. Changes in postcolor number of filter-paper sheets with 15% add-on of fractions from thermally aged hemicellulose derived from various pulps. For comparison, the thermal discoloration of a test sheet of groundwood pulp, gp, is shown. The initial postcolor number represents the increase in color over that of the untreated filter paper a, daylight fluorescent lamps b, black-light fluorescent lamps c, heat (90 °C and 50% rh). Key O, blank filter paper , heated BP A, heated GP V, heated...

Vast amounts of renewable biomass are available for conversion to liquid fuel, ethanol. In order to convert biomass to ethanol, the efficient utilization of both cellulose-derived and hemicellulose-derived carbohydrates is essential. Six-carbon sugars are readily utilized for this purpose. Pentoses, on the other hand, are more difficult to convert. Several metabolic factors limit the efficient utilization of pentoses (xylose and arabinose). Recent developments in the improvement of microbial cultures provide the versatility of conversion of both hexoses and pentoses to ethanol more efficiently. In addition, novel bioprocess technologies offer a promising prospective for the efficient conversion of biomass and recovery of ethanol. 

Development of Agriculture Left-Overs Fine Organic Chemicals from Wheat Hemicellulose-Derived Pentoses... 

Martel F, Estrine B, Plantier-Royon R, Hoffmann N, Portella C (2010) Development of Agriculture Left-Overs Fine Organic Chemicals from Wheat Hemicellulose- Derived Pentoses. In Top Curr Chem. doi 10 1007/128 2010 54... 

Jones, O. T. (2004). The efifect of pH and hemicellulose derived inhibitors on xylitol biosynthesis. Masters thesis, Syracuse University, Syracuse, NY. 

BD (0.35 g/g available sugars). The strain was also able to produce 2,3-BD from dilute-acid-pretreated corn fiber by SSF (0.34 g/g theoretical sugars). Corn-cob molasses, a waste by-product in xylitol production that contained high concentrations of hemicellulose-derived arabinose and xylose, was recently reused as a substrate for production of 2,3-BD using K. pneumoniae (Wang et al., 2010). The maximum... 

The molecular weights of the hemicelluloses and their carboxymethylated derivatives were determined by GPC on a PL aquagel-OH50 column (3007.7 mm. Polymer Laboratories Ltd.). Detection was achieved with a Knauer differential refractometer. The weight of carboxymethylated hemicelluloses became lower than that of native hemicelluloses (26800 g.moP), as the Mw range from 12213 to 15312 g/mol. In addition, carboxymethyl hemicelluloses had a relatively low index of polydispersity (2.75-2.87), which indicated that the molecular weights of hemicellulosic derivatives were more uniform [72]. 

X. Peng, J. Ren, and R. Sun, An efficient method for the synthesis of hemicellulosic derivatives with bifunctional groups in butanol/water medium and their rheological properties, Carbohydr. Polym., 83 (4), 1922-1928, 2011. 

The present article discusses the analytical information that can be obtained by MALDI-MS analysis of different types of non-acetylated and D-acetylated hemicelluloses derived from wood and pulp. Furthermore, a procedure for analyzing the molar mass parameters for hemicelluloses, utilizing size exclusion chromatography (SEC) followed by MALDI-MS analysis, is discussed. 

Figure 9 depicts a schematic representation of the analytical procedure developed by us to characterize the absolute molar mass parameters of hemicelluloses derived from wood and pulp. In this procedure, SEC. separates the hemicellulose into fractions each containing components with a narrow range of molar masses and the accurate peak-average molar mass (Mp) of each fraction is subsequently determined by MALDI-MS. The molar mass parameters for the hemicelluloses are then calculated on basis of the SEC distribution curve and utilizing the MALDI-MS calibrated mass scale. 

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