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 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate the involvement of bacterial enzyme activities in the biotransformation of xenobiotic compounds, we have developed a simulation of the rat hindgut microflora in vitro. This mixed bacterial population exhibits many similarities to the native rat flora, and the diversity of bacterial species and the activity of a number of hydrolytic and reductive enzymes (e.g. azoreductase, beta-glucosidase, beta-glucuronidase, nitrate reductase and nitroreductase) are reproduced in the culture at levels similar to those found in the large intestine. The flora have been found to respond to an anutrient (cyclamate) or to host products (bile acids) with changes in enzyme activity, and to metabolize the azo dye Brown HT to metabolites qualitatively similar to those found in the faeces after oral administration to the rat. The experiments demonstrate that the bacterial population of the large intestine of the rat may be successfully cultured in vitro and provides and alternative to animal studies for the investigation of foreign compound metabolism by the flora.
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PMID:The use of continuous flow systems for studying the metabolic activity of the hindgut microflora in vitro. 243 Aug 72

Brown rot basidiomycetes have long been thought to lack the processive cellulases that release soluble sugars from crystalline cellulose. On the other hand, these fungi remove all of the cellulose, both crystalline and amorphous, from wood when they degrade it. To resolve this discrepancy, we grew Gloeophyllum trabeum on microcrystalline cellulose (Avicel) and purified the major glycosylhydrolases it produced. The most abundant extracellular enzymes in these cultures were a 42-kDa endoglucanase (Cel5A), a 39-kDa xylanase (Xyn10A), and a 28-kDa endoglucanase (Cel12A). Cel5A had significant Avicelase activity--4.5 nmol glucose equivalents released/min/mg protein. It is a processive endoglucanase, because it hydrolyzed Avicel to cellobiose as the major product while introducing only a small proportion of reducing sugars into the remaining, insoluble substrate. Therefore, since G. trabeum is already known to produce a beta-glucosidase, it is now clear that this brown rot fungus produces enzymes capable of yielding assimilable glucose from crystalline cellulose.
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PMID:Processive endoglucanase active in crystalline cellulose hydrolysis by the brown rot basidiomycete Gloeophyllum trabeum. 1587 Mar 28

Brown rot fungi uniquely degrade wood by creating modifications thought to aid in the selective removal of polysaccharides by an incomplete cellulase suite. This naturally successful mechanism offers potential for current bioprocessing applications. To test the efficacy of brown rot cellulases, southern yellow pine wood blocks were first degraded by the brown rot fungus Gloeophyllum trabeum for 0, 2, 4, and 6 weeks. Characterization of the pine constituents revealed brown rot decay patterns, with selective polysaccharide removal as lignin compositions increased. G. trabeum liquid and solid state cellulase extracts, as well as a commercial Trichoderma reesei extract (Celluclast 1.5 L), were used to saccharify this pretreated material, using beta-glucosidase amendment to remove limitation of cellobiose-to-glucose conversion. Conditions varied according to source and concentration of cellulase extract and to pH (3.0 vs. 4.8). Hydrolysis yields were maximized using solid state G. trabeum extracts at a pH of 4.8. However, the extent of glucose release was low and was not significantly altered when cellulase loading levels were increased threefold. Furthermore, Celluclast 1.5 L continually outperformed G. trabeum cellulase extracts, although extent of glucose release never exceeded 22.0%. Results suggest methodological advances for utilizing crude G. trabeum cellulases and imply that the suboptimal hydrolysis levels obtained with G. trabeum and Celluclast 1.5 L cellulases, even at high loading levels, may be due to brown rot modifications insufficiently distributed throughout the pretreated material.
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PMID:Assessment of saccharification efficacy in the cellulase system of the brown rot fungus Gloeophyllum trabeum. 2017 87