Abstract: We described two convenient assay methods to estimate bile acid deconjugation and bile acid bioconversion at the 7alpha-OH position by individual microorganisms grown in media containing taurocholic acid. The methods are based on (i) a selective chemical assay for taurine conjugates previously described and (ii) the use of a cell-free preparation of 7alpha-hydroxysteroid dehydrogenase from Escherichia coli to directly quantify 7alpha-OH groups. These non-chromatographic approaches have been applied to the study of three model strains of intestinal organisms, E. coli, Bacteroides fragilis, and Clostridium perfringens, grown in standard media in the presence of purified tritiated taurocholate. Assay results were confirmed by thin-layer chromatography solvent systems designed to separate conjugated from unconjugated bile acid and unmodified cholic acid nucleus from 7alpha-OH bioconversion product(s) (primarily 3alpha, 12alpha dihydroxy, 7-keto-cholanoic acid). In addition, 7alpha-hydroxysteroid dehydrogenase activity was demonstrated in cell-free extracts of all three organisms. Of the three organisms, only C. perfringens was demonstrated to (i) deconjugate taurocholic acid, (ii) contain 3alpha-hydroxysteroid dehydrogenase activity, (iii) convert cholic acid into at least five labeled metabolites visible on thin-layer chromatography, and (iv) catalyze significant tritium exchange with water in the medium.

Abstract: The role of the wood pathologist differs from that of other plant pathologists in that its concern lies in the study of the effects of microorganisms on the dead tissues of woody plants--tissues in which lignin is a major component. The main goal of wood pathologists, of course, is to thwart biodeterioration. Recently, however, at the U.S. Forest Products Laboratory, at the Swedish Forest Products Laboratory, and at several industrial laboratories, a second goal has emerged--to use wood-attacking microorganisms beneficially, i.e. for the bioconversion of wood.

Abstract: The Simplex method of optimization was applied to the bioconversion of DL-Homoserine into L-Threonine byEnterobacter cloacae resting-cells in a 2 1 fermentor.

Abstract: SummaryThe bioconversion from DL-Homoserine to L-Threonine byEnterobacter cloacae resting-cells is directed by various parameters: concentration in cells, in homoserine, in glucose, temperature, shaking, pH, and time.Some of them, such as temperature, shaking, and pH were determined during preliminary tests.In order to consider the reciprocal effect of the other parameters, we applied an experimental scheme based on the simultaneous variation of all parameters of the process.The method of factorial designs is based on the choice of an experimental field for which we make a matrix of the experiments. The measured result is the yield of L-Threonine produced in relation to L-Homoserine employed.The computational interpretation of the results gives the levels of significance of every parameter and the direction of the variation needed to improve the yield.This method permits us to obtain information which may be interpreted immediately, with a reduced number of experiments.