Cellobiose conversion

Proceeding on the same line, Hagerdal et al. reported that perfluorinated resin supported sulfonic sites (NATION 501) can hydrolyze disaccharides [25]. In particular, these authors studied the effect of the addition of sodium chloride in the hydrolysis of cellobiose, a subunit of cellulose much more resistant to hydrolysis than sucrose. They observed that the presence of sodium chloride in water dramatically increased the conversion of cellobiose. Indeed, in the presence of 10 wt% of sodium chloride, 80% of cellobiose was converted at 95°C after 6 h. For comparison, when 1% of sodium chloride was added, only 50% of cellobiose was hydrolyzed. It should be noted that without addition of sodium chloride only 15% conversion was achieved, thus pushing forward the key role of sodium chloride on the reaction rate. Effect of salt on the reaction rate was attributed to a change of the pH caused by the release of proton in the reaction medium (due to an exchange of the supported proton by sodium). 

Fig. 6. Cellulose conversion over time for the same experiments as shown in Fig. 5. The data represent cellulose conversions based on glucose production alone. Cellobiose measurements taken at the end of the experiments account for an additional conversion of about 4%. Error bars represent averages 1 SD for three repeated experiments.

Hausoul et al. [60] also reported on telomerization with aldopentoses (D-xylose, L-arabinose), aldohexoses (D-glucose, D-mannose, D-galactose), ketohexoses (d-fructose, L-sorbose) and the disaccharides D-sucrose and cellobiose, using Pd/ TOMPP as catalyst without the addition of base in /V,/V-di methyl acetamide as the solvent (Fig. 15). The Pd/TOMPP combination had previously been shown to be highly active in the telomerization of various polyols (vide supra). Good conversion... 

The treatment of cellobial with perbenzoic acid and water leads predominantly to 4-( 8-D-glucopyranosyl)-D-mannose.38 On the other hand, the treatment of hexaacetylcellobial in the same manner leads predominantly to cellobiose, which has been isolated as the octaacetyl derivative. Hexaacetylcellobial has also been made from the synthetically prepared epicellobiose, and the conversion of hexaacetylcellobial to cellobiose has completed the total synthesis of this important sugar.17... 

Various authors have shown that non-ionic surfactants have a beneficial effect on the hydrolysis of cellulosic and lignocellulosic substrates, whereas anionic and cationic surfactants alone interfere negatively (Castanon and Wilke, 1981 Helle et al, 1993 Park et al, 1992 Ooshima et al., 1986 Traore and Buschle-Diller, 1999 Ueda el al., 1994 Eriksson el al., 2002). Increases in the amount of reducing soluble sugars and substrate conversion were reported. The effect depends on the substrate and is not observed for soluble substrates, such as carboxymethylcellulose or cellobiose. Nonionic surfactants increased the initial rate of hydrolysis of Sigmacell 100, and when they were added later in the process they were less effective (Helle et al, 1993). They same authors found also that the addition of cellulose increases the critical micelle concentration of the surfactant, which indicates that the surfactant adsorbs to the substrate. Surfactants are more effective at lower enzyme loads and reduce the amount of adsorbed protein (Castanon and Wilke, 1981 Ooshima et al, 1986 Helle et al, 1993 Eriksson et al., 2002) which can be used to increase desorption of cellulase from the cellulosic substrate (Otter et al., 1989). Anyhow, the use of surfactants to enhance desorption of cellulases from textile substrates in order to recover and recycle cellulases was not successful (Azevedo et al., 2002b). 

At present cellobiose is not a practical substrate for amylose production, but the enzymatic degradation of cellulose is extensively studiedand the conversion of cellobiose into amylose by the CBP-GP system should be the important way to convert cellulosic biomass into value-added materials and products. 

Kitaoka, M., Sasaki, T., and Taniguchi, H. 1992. Conversion of sucrose into cellobiose using sucrose phosphorylase, xylose isomerase and cellobiose phosphorylase. Denpun Kagaku, 39, 281-283. 

The solubility of the trityl ethers is of advantage in experimental work. For example, during the conversion of methyl 2,3,4-triacetyl-/3-D-glucopyranoside to the 2,3,6-triacetate (see page 95) there is formed an equilibrium mixture of these two substances from which the compound with the free 4-hydroxyl group can be separated only in poor yield by simple crystallization. Separation is more complete when the mixture is tritylated in the ordinary way with trityl chloride in pyridine. Tritylation occtirs almost exclusively at the 6-hydroxyl of the 2,3,4-triacetate, the 6-trityl ether thus formed being insoluble in water. The untritylated 2,3,6-triacetate can then be extracted and is obtained in good yield. It is of interest as an intermediate in the synthesis of cellobiose. 

This table shows that (i) 188 strains used neither substrate, and 288 used both cellobiose and salicin (it) 9 strains used cellobiose, but not salicin (tit) 11 strains used salicin, but not cellobiose. Thus, with only 20 exceptions (4%), a yeast that utilizes salicin also utilizes cellobiose, and conversely. Provided that the /S-D-glucosidases are equally accessible to the /3-D-glucopyranosides, this result is to be... 

The photosynthetic bacterium R. marinum A-501, which was considered to be the main (or only) H2 producer in BC1, could utilize various organic substrates for the photoproduction of H2 (Table 2). However, among the substrates tested, starch, cellobiose and acetic acid, which are utilized by BC1 as substrates for H2 production, could not be used for H2 production by a pure culture of strain A-501. The results indicate that the conversions of starch, cellobiose and acetic acid into H, require the contribution of other bacteria in BC1. Among the isolated strains, only V. fluvialis T-522 and T-59 possessed starch-degrading activity. This result suggests that V. fluvialis T-522 and T-59 contribute to the degradation of starch to supply some substrate(s) in a form that can be readily utilized by R. marinum A-501 for H2 production. 

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