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Abstract: Bamboo is an alternative feedstock for the production of fine chemicals, such as fuel ethanol and lactic acid, because bamboo has a large amount of sugars. An effective pretreatment method for enzyme saccharification is required for the efficient production of these materials. Enzyme saccharification (48h) using a 35atm and 5min steam exploded bamboo produced 426 and 488mg/(g initial dry sample) of glucose and reducing sugar, respectively. In addition, pretreatments using 20atm and 5min steam explosion or mechanical milling for 5min followed by 10wt.% sodium hydroxide treatment at 121°C for 60min were attempted in order to enhance the digestibility of the holocellulose component. Both of these pretreatment methods had a large positive effect on the production of sugars by subsequent enzymatic hydrolysis. In particular, the maximum value of glucose production was obtained by the 20atm steam explosion and 10wt.% sodium hydroxide treatment. This produced 456mg/(g initial dry sample) of glucose and 460mg/(g initial dry sample) of reducing sugar. In comparison, the mechanical milling and 10wt.% sodium hydroxide treatment produced 383 and 485mg/(g initial dry sample) of glucose and reducing sugar, respectively. From these results, it was concluded that the pretreatment with 20atm steam explosion and 10wt.% sodium hydroxide treatment was the most effective pretreatment method for the production of glucose from bamboo by enzyme saccharification. However, since this pretreatment method requires the severe conditions of both high pressure and temperature steam explosion and high concentration sodium hydroxide, an alkaline peroxide pretreatment without a steam explosion and high concentration sodium hydroxide was also attempted. A comparatively large amounts of glucose and reducing sugar production, i.e. 399 and 568mg/(g initial dry sample), respectively, were obtained in 1%(v/v) hydrogen peroxide and 1wt.% sodium hydroxide treatment at 90°C for 60min. Therefore, it was concluded that alkaline peroxide pretreatment is an effective and environmentally friendly method for the enzyme saccharification of bamboo. [Copyright &y& Elsevier]

Over 90% of the original hemicelluloses in the cell walls of bagasse were sequentially extracted with distilled water, 0.5 M NaOH, 0.5, 1.0, 1.5, 2.0 and 3.0% H2O2 at pH 11.5, and 2.0 M NaOH at 55 °C for 2 h. Meanwhile, the successive treatments also released 89.0% of the original lignin. Chemical composition, physico-chemical properties, and structures of the eight hemicelluloses were elucidated by a combination of sugar analysis, nitrobenzene oxidation of bound lignin, molecular determination, Fourier transform infrared, and 1H and 13C NMR spectroscopy and thermal analysis and the results are reported. The results showed that the sequential treatments were very effective on the fractionation of hemicelluloses from bagasse, and the extraction strength, such as alkali and H2O2 concentration, had a great influence on the chemical and structural features of the hemicelluloses, e.g. content of associated lignin and molecular weight. The hemicellulosic fraction, isolated with 0.5% H2O2 at pH 11.5 for 2 h under 55 °C, had a backbone of xylose residues with β-(1→4) linkages and were branched mainly through arabinofuranosyl and 4-O-methyl glucopyranosyl units. Ferulic and p-coumaric acids were found to be esterified to the hemicelluloses. [Copyright &y& Elsevier]

Eight hemicellulosic fractions were obtained by sequential treatment of dewaxed barley straw with 0.1 M NaOH at 45 °C for 3 h, 0.25, 0.5, 1.0, 1.5, 2.0, and 3.0% H2O2 at 45 °C for 3 h at pH 11.5, and 10% KOH–1% Na2B4O7·10H2O at 28 °C for 15 h under continuous agitation. The yields of the fractions were 8.0, 3.1, 3.3, 3.3, 2.2, 2.0, 2.0, and 9.9%, respectively, of the initial amount of barley straw, corresponding to the dissolution of 21.6, 8.4, 8.9, 8.9, 5.9, 5.4, 5.4, and 26.7% of the original hemicelluloses. Meanwhile, the successive treatment also solubilized 29.1, 15.8, 14.6, 10.8, 4.5, 3.2, 2.7, and 3.7% of the original lignin, respectively. This sequential extraction together resulted in dissolution of 91.1% of the original hemicelluloses and 84.8% of the original lignin. The 0.1 M NaOH-soluble hemicellulosic fraction contained mainly xylose, glucose, and arabinose, 44.2, 15.7, and 15.2%, respectively, while the 10% KOH–1% Na2B4O7·10H2O-soluble fraction predominated in xylose, 75.0%. The six alkaline peroxide-soluble fractions were composed of 50.3–54.4% xylose, 14.7–16.9% arabinose, 6.8–10.7% glucose, 6.8–8.5% glucuronic acid or 4-O-methyl-d-glucuronic acid, 0.4–1.5% mannose, and 0.3–1.2% rhamnose. All the hemicellulosic fractions contained substantial amounts of glucuronoarabinoxylans and noticeable quantities of β-glucans. In comparison, the six hemicellulosic fractions, isolated with alkaline peroxide, had much higher molecular weights (56,890–63,810 g mol−1) than those of the two hemicellulosic preparations (28,000–29,080 g mol−1), isolated with alkali in the absence of hydrogen peroxide. The thermal stability of the hemicelluloses increased with an increment of their molar mass. [Copyright &y& Elsevier]