Improvements of the bioavailability of straw: acid and enzyme hydrolysis of wheat straw pretreated with saturated lithium chloride in hydrochloric acid

Wheat straw was pretreated with saturated lithium chloride in 4 m hydrochloric acid at 50°C for 1 h, then hydrolysed at 100°C for 1 min, to give 84% conversion to monosaccharides. Particle sizes, 150–355 mesh, were easily hydrolysed. Samples pretreated with saturated lithium chloride in 1 m hydrochloric acid at 27°C for 24 h were hydrolysed by Trichoderma viride cellulase (MVA 1284) [1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] to give 20–23% monosaccharides for particle sizes of 150–250 mesh, and 82–95.4% for particle sizes of 250–355 mesh.     

Acid and enzymic hydrolysis of chaotropically pretreated millet stalk,acha and rice straws and conversion of the products to ethanol

Successful attempts have been made using acid and enzyme hydrolyses and chaotropic ions to solubilize some common but valuable sources of cellulose which are somewhat inaccessible to useful conventional degradative reagents/systems. Millet stalk, acha and rice straw (15% w/v) were incubated at 50°C for 1 h in 4 m hydrochloric acid saturated in lithium chloride, then hydrolysed for 45–60 s at 100°C, to yield maximally 79.2, 84.0 and 74.7% hydrolysis products for the three straws, respectively. Samples incubated in 1 m hydrochloric acid, containing saturated lithium chloride for 24 h at 27°C, washed thoroughly, freeze dried, then hydrolysed (0.5% w/v) with 0.4% w/v Trichoderma viride cellulase MVA 1284 [see 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] gave 16.4, 34.4 and 52.8% hydrolysis products for millet stalk, acha and rice straw, respectively. In general conversion of hydrolysed products direct to ethanol may be difficult as yeasts cannot grow in high salt concentrations resulting from acid hydrolyses. Growth response curves for two strains of Saccharomyces cerevisiae show the results of prior removal of chaotropic ions for successful growth of the organisms on the hydrolysates.     

The structures of an α-l-arabinosyl-β-d-xylotriose and -tetraose obtained from hemicellulose by enzymic hydrolysis by an extracellular hemicellulase produced by Cephalosporium sacchari

An extracellular endohemicellulase III from Cephalosporium sacchari degraded spear-grass (Heteropogon contortus) hemicellulose B to a series of mixed oligosaccharides. Two neutral oligosaccharides, AraXyl₃ and AraXyl₄, were isolated by preparative paper-chromatography, and characterised by enzymic and permethylation techniques.     

Production and purification of two Himecellulases from Cephalosporium sacchari

The production of extracellular hemicellulases by the fungus Cephalosporiumsacchari was studied in the presence of various sources of carbon and at various initial pH values and temperatures. Hemicellulose B and holocellulose from spear grass (Heteropogon contortus) were the best sources of carbon, and the optimum temperature was 27°. The initial pH value had little influence on the final yield of hemicellulases. Two hemicellulases (HC-III and HC-IV) were purified by ammonium sulphate precipitation and isoelectric focusing. Their molecular weights were 10.700 and 9,550, and their pI values 9.40 and 6.0, respectively. HC-III hydrolysed hemicellulose B to oligosaccharides without production of monosaccharides.