Hemicellulose ratio

The chemical composition of the fibers influences their susceptibility to microorganism growth. Lignin content offers some protection, as evidenced by the high resistance of coir fibers, which contain 35% lignin. The lignin-hemicellulose ratio, the crystalline content of cellulose fraction, and the presence of micronutrients are other factors that determine the extent of microorganism activity on the fibers. 

Of samples swollen with ethylene diamine, the graft yield at a 50 1 liquor ratio increases as the concentration of ethylene diamine increases. This is due to the increase of decrystallization of swollen samples, which helps the penetration velocity of the chemicals through the cellulosic chains. Graftability of the samples treated with 100% ethylene diamine is lower that of the sample treated with 75%. This is due to the dissolution of low DP chains and some of the hemicelluloses, which is detectable by the increase in DP of the sample teated with 100% ethylene diamine. 

Recently, the alkah-soluble hemicelluloses of hardwood dissolving pulps have been investigated [28]. Their composition and molecular properties depended on the pulp origin and steeping conditions. The MGX of the j8-fraction from press lye had a low uronic acid content (ratio of MeGlcA to Xyl is about 1 20). The molecular weight of the hemicellulose fractions varied between 5000 and lOOOOg/mol. 

Each fruit has specific quantities and ratio of pectin, hemicelluloses and cellulose. These polysaccharides are important concerning enzymes activities required to produce juices and concentrates. Moreover, even if molecular weight and methylation degree of the pectin are specific for each fruit, during the fruit maturation, endogenous pectinases depolymerases and esterase are changing the pectin characteristics This broad variability of raw material makes difficult the standardisation of fruits processing. 

FTIR spectra of extracted wheat straw hemicellulose and cellulose do not exhibit this band (spectra not shown). From this point, the extracted wheat straw XRPP is also assigned to pectic substances. The intensity ratio of the bands i>as(COO ) at 1608 cm" and j (C 0) ester at 1740 cm corresponds to fully deesterified pectin and Me pectate... 

Hardwood xylans and xylans of annual plants may contain up to 7% O-bound acetyl groups. Seven out of ten xylose residues in native hardwood xylan are acetylated on C-2 and/or C-3 (10). Because of the possible migration of O-acetyl groups between 2- and 3-positions during and after isolation of hemicellulose components, it is difficult to determine their original distribution in nature (11). The ratios reported for 2-, 3-, and 2,3-positions of acetyl groups in birch xylan have been 2 4 1 (3) and 2 2 1 (10) and in bracatinga xylan 3 3 1 (12). 

Substrate and Pretreatment. Sweet corn (hybrid Lingodor) of W.H. Perron Laval, Quebec was grown in well prepared soil in a plot of 3 x 2 meters. Corn stalks were ground to 20 mesh to be used as a substrate. It was pretreated with 1.5% sodium hydroxide (NaOH) wt/vol with substraterwater ratio of 1 10 at 121 C for 60 minutes. The substrate was not washed after the pretreatment, and all the solubilized polymers (hemicelluloses and lignin) were retained along with the insoluble polymer (cellulose) in the fermentation medium. The composition of corn stalk is presented in Table 1. 

Samples of the sugars being removed are cooled to 20°C. and tested for density by a sugar Brix spindle., Analysis of these solutions shows that the reducing sugar content of the solutions is 60 to 70% of the concentration shown by the Brix spindle. If the hydrolysis of hemicellulose is not complete, the ratio of reducing sugar to Brix will be low and will indicate that insufficient acid has been used. 

Comparison of Cellulose/Hemicellulose, Glucan/Xylan, and Xylan Degradation/Glucan Degradation Ratios for Preliminary Tests (4) at 0.77 g of HzO/g of Dry Stems ... 

C/H, cellulose/hemicellulose composition ratio G/X, glucan/xylan composition ratio AX/AG, xylan/glucan degradation ratio (this ratio was calculated assuming little change in the sum of ash, lignin, and extractives). 

Starch-free BSG was subjected to reaction with water (autohydrolysis) in a 2-L stainless steel Parr reactor model 4532 (Moline, IL), to cause the hydrolytic degradation of hemicelluloses, operating under optimized conditions (liquid-to-solid ratio of 8 1 [w/w], standard heating temperature profile up to 190°C, isothermal reaction at 190°C for 2.5 min) (2). After the reactor was cooled down, the oligosaccharide-containing liquor (OCL) was separated from the residual solid by filtration (Whatman no. 1 filter paper). 

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