Wheat hemicellulose from straw

Table I. Growth of Trichoderma reesei QM9414 (Tr) and T. harzianum IMI275950 (Th) on wheat straw lignocellulose (lignocell.) or derived cellulosic materials from straw (cell., cellulose hemicell-A, hemicellulose-A holocell., holocellulose)...

Hemicelluloses From Wheat Bran and Straw to Pentoses.81... 

Hemicellulose Fig. 3 Scheme for extraction of hemicelluloses from ground wheat straw... 

A sample of 5 g dry ground straw was treated with 200 ml NaOH solution (concentrations of 0.25 and 0.50 mol/l) for 2 h at different temperatures (30 and 55 °C). After the indicated period of treatment, the sample was acidified to pH 5 with glacial acetic acid, concentrated to about 30 ml under reduced pressure, and then filtered. The alkali-soluble hemicelluloses were then precipitated by pouring the concentrated supernatant fluid with four volumes of 95% ethanol (20 °C, 24 h). The precipitates were recovered by filtration, washed with 70% ethanol, and air dried. The scheme for fractionation of hemicelluloses from wheat straw is illustrated in Fig. 3. 

Isol. from partial acid hydrolysates of gum chagual (Puya spp.) and the hemicelluloses from corn hulls, wheat straw, wheat bran and maritime pine (Pinus pinaster). Amorph. -hlOl (88) (H2O). 

CiiHigOii 326.257 Isol. from partial acid hydrolysates of sunflower (Helianthus annuus) head hemicellulose, from pear cell-wall xylan, from various wheat-straw preparations and from corn hulls. 

Sun, R.C. Fang J. M. Tomkinson, J. Stearoylation of hemicelluloses from wheat straw. Polym. Degrad. Stab. 2000, 67, 345-353. 

AGX are also the dominant hemicelluloses in the cell walls of hgnified supporting tissues of grasses and cereals. They were isolated from sisal, corncobs and the straw from various wheat species [4]. A more recent study on corncob xylans [30] showed the presence of a hnear, water-insoluble polymer... 

Potential resources of xylans are by-products produced in forestry and the pulp and paper industries (forest chips, wood meal and shavings), where GX and AGX comprise 25-35% of the biomass as well as annual crops (straw, stalks, husk, hulls, bran, etc.), which consist of 25-50% AX, AGX, GAX, and CHX [4]. New results were reported for xylans isolated from flax fiber [16,68], abaca fiber [69], wheat straw [70,71], sugar beet pulp [21,72], sugarcane bagasse [73], rice straw [74], wheat bran [35,75], and jute bast fiber [18]. Recently, about 39% hemicelluloses were extracted from vetiver grasses [76]. 

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... 

Aqueous alkaline extraction of wood was employed by Poumarede and Figuier48 in 1846 for the removal of a substance called wood gum. Similar very crude xylan or hemicellulose preparations were made by other workers of the early period. Extractions were made not only from wood sawdust, but from annual plant materials such as wheat straw, corn cob, etc.49-66... 

When the hyper-cellulolytic mutant T. reesei QM9414 was grown on various substrates derived from wheat straw in stirred batch culture, the highest specific growth rates were on holocellulose and the hemicellulose-A defined by O Dwyer (8) it grew poorly on lignocellulose. By contrast,... 

However, oral administration of these polysaccharides had no effect. Hemi-celluloses from different higher plants caused regression of solid Sarkoma 180 in mice but not of ascites tumor. Arabinoglucuronoxylan isolated from wheat-straw hemicellulose was completely devoid of activity, whereas arabinoglucoxylan was highly active (Nakahara 31)). 

When screening a large number of Lactobacillus strains for lactate production using hemicellulose hydrolysate, strains L. pentosus CHCC2355 and L. brevis CHCC2097 were selected and evaluated further (Garde et al, 2002). Each strain produced lactate with 88% (for L. pentosus) and 61% of the theoretical yield (L. brevis), respectively, from wheat straw hydrolysate without visible inhibition. The operation of the phosphoketolase pathway in these... 

Garde, A., Jonsson, G., Schmidt, A. S., and Ahring, B. K. 2002. Lactic acid production from wheat straw hemicellulose hydrolysate by Lactobacillus pentosus and Lactobacillus brevis. Bioresour. Technol., 81,217-223. 

XOS are manufactured by enzymatic hydrolysis of xylan from corn cobs, oat spelt xylan or wheat arabinoxylan [257]. Xylan, a principle t)q)e of hemicellulose exists as a linear polymer of -D-xylopyranosyl units linked by 1 4 glycosidic bonds. Depending on the origin, different substituents such as arabinfuranosyl, 4-0-methylglucuronosyl and acetyl groups are present. Typical raw materials for XOS production include hardwoods, com cobs, straws. 

Using the advanced bioethanol technology available, it is possible to produce ethanol from any cellulose/hemicellulose material, which means any plant or plant-derived material. Many of these materials are not just underutilized and inexpensive, but also create disposal problems. For example, rice straw and wheat straw are often burned in the field, a practice that is becoming limited by air pollution concerns. Also, much of the material now going into landfills is cellulose/hemicellulose material and could be used... 

Biomass material (woodchips or wheat straw) is placed in a high-pressure stainless steel tube and exposed to steam under pressures ranging from 250-650 psi at 200 to 240°C for up to 20 min. The sudden pressure release causes an explosion of biomass material thereby disrupting the lignin and hemicellulose bonding toward cellulose. Many investigators (see [29] for review) have studied the steam explosion of biomass materials. The addition of SO2 enhances the pretreatment effect and also increases the recovery of hemicellulose [34-36]. A refinement of this pretreatment method has recently been reported by Stenberg et al. [37]. 

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