Background: Mutation of Trp-40 in the Cel7A cellobiohydrolase from Trichoderma reesei (TrCel7A) causes a loss of crystalline cellulose-degrading ability. Results: Mutant W40A showed reduced specific activity for crystalline cellulose and diffused the cellulose chain from the entrance of the active site tunnel. Conclusion: Trp-40 is essential for chain end loading to initiate processive hydrolysis of TrCel7A. Significance: The mechanisms of crystalline polysaccharide degradation are clarified.

cDNAs encoding two glycoside hydrolase family 1 beta-glucosidases (BGL1A and BGL1B) were cloned from the basidiomycete Phanerochaete chrysosporium, and the substrate specificities of the recombinant enzymes and the expression patterns of the two genes were investigated in relation to cellobiose metabolism by the fungus. The cDNA sequences contained open reading frames of 1,389 base pairs (bp) (bgl1A) and 1,623 bp (bgl1B), encoding 462 and 530 amino acids, respectively. Although high sequence identity (65%) was observed between the deduced amino acid sequences of the two enzymes, an apparent difference was observed at the C-terminal region: BGL1B has a 63-amino acid extension, which has no similarity with any known protein. Both recombinant enzymes expressed in Escherichia coli showed hydrolytic activity towards several beta-glycosidic compounds. However, the substrate recognition patterns of the two enzymes were quite different from each other. In particular, cellobiose was hydrolyzed more effectively by BGL1B than by BGL1A. The expression of the two genes in the fungus was monitored by reverse transcription-PCR, which showed that bgl1A was expressed constitutively in both glucose- and cellobiose-containing culture, whereas bgl1B was expressed in cellobiose culture but was repressed in glucose culture, possibly because of carbon catabolite repression. We conclude that BGL1B contributes to cellobiose metabolism during cellulose degradation by P. chrysosporium.

The white-rot fungus Phanerochaete chrysosporium has two intracellular b-glucosidases (BGL1A and BGL1B) belonging to glycoside hydrolase (GH) family 1. BGL1B effectively hydrolyzes cellobiose and cellobionolactone, but BGL1A does not. We have determined the crystal structure of BGL1A in substrate-free and gluconolactone complexed forms. The overall structure and the characteristic of subsite À1 (glycone site) were similar to those of other known GH1 enzymes. The loop regions covering on the (b/a) 8 barrel was significantly deviated, and they form a unique subsite +1 (aglycone site) of BGL1A.

Abstract. There are two kinds of higher-order extensions of model checking: HORS model checking and HFL model checking. Whilst the former has been applied to automated verification of higher-order functional programs, applications of the latter have not been well studied. In the present paper, we show that various verification problems for functional programs, including may/must-reachability, trace properties, and linear-time temporal properties (and their negations), can be naturally reduced to (extended) HFL model checking. The reductions yield a sound and complete logical characterization of those program properties. Compared with the previous approaches based on HORS model checking, our approach provides a more uniform, streamlined method for higher-order program verification.

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This paper introduces a variant of the resource calculus, the rigid resource calculus, in which a permutation of elements in a bag is distinct from but isomorphic to the original bag. It is designed so that the Taylor expansion within it coincides with the interpretation by generalised species of Fiore et al., which generalises both Joyal's combinatorial species and Girard's normal functors, and which can be seen as a proofrelevant extension of the relational model. As an application, we prove the commutation between computing Böhm trees and (standard) Taylor expansions for a particular nondeterministic calculus.

To increase the uranium recovery rate of molten salt electrorefining step in pyrometallurgical reprocessing of metallic fast reactor fuels, tests were carried out using electrorefiners equipped with mechanisms for scraping cathode deposits. After the modifications in the design of the anode basket and scraper mechanism, no stalling of the anode and scraper rotation due to interference by cathode deposits occurred. Under the condition that codissolution of zirconium and uranium was allowed in order to obtain maximum throughput, a current of 400-450 A was maintained until 82% of the initially loaded uranium was recovered. The uranium recovery rate for the same duration reached 789 g U/h (32.9 g U/hÁL per electrode volume). On the assumption that an electrorefiner operates for 20 h/d and 200 d/y in an actual pyrometallugical reprocessing facility, this result corresponds to a uranium recovery rate of 3.16 t U/y using only one electrode assembly of about 30 cm diameter, which should be a sufficiently high performance for practical use. From these results, the engineering feasibility of uranium recovery using an electrorefiner with cathode deposit scraper mechanism has been demonstrated.

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