Release of alkali and alkaline earth metallic (AAEM) species was examined during pyrolysis of pulverized pine and sugarcane bagasse. The use of a wire-mesh reactor enabled the investigation of the primary release of AAEM species from pyrolyzing particles suppressing secondary interaction between them. Upon heating the pine at 1000°C s -1 up to 800°C, 15-20% of each AAEM species was released during the tar evolution and afterward. Further isothermal heating caused nearly complete release of alkalis within 150 s, while the release of alkaline earths terminated at levels of 20-40%. Heating the pine at 1°C s -1 up to 800°C brought about the release of AAEM species mainly after the tar evolution. Chlorides of AAEM species were found to be very minor volatiles over the range of conditions. Variations in K release with operating variables were reasonably explained by considering that elemental K volatilized from the charbonded AAEM species was a major volatile K species. None of AAEM species were significantly released when a fixed bed of the pine was heated at 1°C s -1 up to 900°C without forced gas flow through the bed. It was suggested that repeated desorption from and adsorption onto the char surface within the fixed bed inhibited the release of AAEM species from the fixed bed and resultantly allowed them to transform into thermally stable char-bonded ones and/or nonvolatiles such as silicates.

Crystal structures of endopolygalacturonase from Stereum purpureum were solved in native and two galacturonic acid complex states at atomic resolution. Endopolygalacturonase catalyzes the hydrolysis of alpha-1,4-glycosidic linkage of polygalacturonate in pectin. The native structure was determined by the multiple wavelength anomalous dispersion method and was refined anisotropically with SHELXL-97, with an R factor of 11.4% and an R(free) factor of 14.0% at 0.96 A resolution. The enzyme folds into a right-handed parallel beta-helix with 10 complete turns. The crystal structures of its binary complex with one D-galacturonate and its ternary complex with two D-galacturonates were also determined to identify the substrate binding site at 1.0 and 1.15 A resolutions, respectively. In the binary complex, one beta-D-galactopyranuronate was found in the +1 subsite, thus proving the strong affinity of the +1 subsite expected from the bond cleavage frequency on oligogalacturonates. In the ternary complex, an additional beta-D-galactofuranuronate was found in the -1 subsite. In both subsites, the recognition of the galacturonate carboxy group is important in galacturonate binding. In the +1 subsite, the carboxy group interacts with three basic residues, His195, Arg226, and Lys228, which were conserved in all endopolygalacturonases. In the -1 subsite, the unique nonprolyl cis-peptide bond is believed to be involved in binding the carboxy group of the substrate. The active site architecture of the complexes provides insight into the mechanism of inverting glycosyl hydrolases and also sheds light on the basis of the differences between the family 28 and the other inverting glycosyl hydrolases.

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