Breakthrough performance of stacks of dye-cellulosic fabric in affinity chromatography of lysozyme.

The breakthrough performance of stacks of dye-cellulosic fabric in affinity chromatography of lysozyme was investigated in batch and flow experiments. Breakthrough curves were significantly affected by flow rate and were not dependent on the feed solution concentration. System dispersion curves could not explain the flow-rate dependence. Breakthrough curves were analyzed by coupling the kinetic model for pore mass transfer as the only controlling resistance and a system dispersion model. From the analysis, pore film mass transfer resistance was found to be the leading rate-limiting factor when the residence time in the column is greater than 5 min. The model was used to predict the operating and design parameters needed to obtain sharp breakthrough curves. Selectivity studies using lysozyme and bovine serum albumin mixtures showed a high system selectivity for lysozyme.

Draw-fill batch culture mode for production of xylanases by Cellulomonas flavigena on sugar cane bagasse.

Draw-fill culture was evaluated as a method for xylanase production by Cellulomonas flavigena on sugar cane bagasse. Specific xylanase activity and volumetric xylanase activities were measured by harvesting 50%, 55%, 60% and 70% of fermented broth at the end of each subculture. Maximum specific (64 IU mg(-1) protein) and volumetric (166 IU ml(-1)) xylanase activities were obtained by harvesting 50-55% of broth. Values were 3.4 and 3.8 times greater than those obtained in batch cultures carried out under the same conditions. Enzyme productivity of 4.2 IU ml(-1) h(-1) was significantly greater than that obtained in continuous cultures (2.4 IU ml(-1) h(-1)) (P<0.05).

Biotransformation of n-hexadecane by cell suspension cultures of Cinchona robusta and Dioscorea composita.

This manuscript evaluates the phytotoxicity and biotransformation of n-hexadecane as well as peroxidase activity and cytochrome P450 concentration in microsomes for cell suspension cultures of Cinchona robusta and Dioscorea composita. Phytotoxicity was evaluated based on viability and growth. Cell cultures were exposed to a 2 and 4% (v/v) dose of n-hexadecane. The biotransformation of n-hexadecane was determined based on labeled recovery in polar, nonpolar, and cell residue fractions after cell culture extraction during exponential cell growth phase and stationary phase. Differences were observed in accumulation of label during cell growth phase and stationary phase for the cells of the two plants. Differences also were observed between phases for label in polar and nonpolar fractions. Thin-layer chromatography determined labeled intermediates and some were identified. The activity of peroxidase and concentration of cytochrome P450 was lower in C. robusta than in controls and greater in D. composita than in controls. In vitro biotransformation was not successful.

Mechanisms of regulation of urease biosynthesis in Proteus rettgeri.

Urease of Proteus rettgeri is an inducible enzyme synthesized specifically in the presence of urea; urea analogues did not act as inducers. Once initiated, the biosynthesis of the enzyme proceeded as a constant fraction of the total protein formed. The rate of urease formation was affected by the carbon source used. In comparison with glycerol, glucose inhibited enzyme synthesis. The addition of ammonium ions to the inducing medium also decreased the rate of urease biosynthesis, and when ammonium ions were present urease activity and urea transport across the cell membrane were inhibited. A kinetic analysis of urease inhibition by ammonium ions, by use of a partially purified preparation of urease, showed that it was a competitive inhibition.