Robert W. Silman

CMCase production by Spicellum roseum in liquid and solid culture

SummaryCMCase was produced by 7 strains of Spicellum roseum in both liquid and wheat bran solid substrate cultures. No growth occurred above 35°C. Maximum enzyme production occurred at 30°C, whereas best enzyme activity occurred at pH 5.0 and 50°C. In liquid cultures of S. roseum, NRRL strains 13103, 13104, and 13106 produced activities of ca. 1.1, 1.5, and 1.5 mg glucose per hr/ml culture supernate at 1 week and 2.9, 1.5, and 2.1, respectively at 3 weeks compared to Trichoderma reesei NRRL 11236 (MCG77), which produced activities of 2.8 and 1.3 at 1 and 3 weeks.

Viability and initial kinetic parameters for dry yeast inocula in batch fermentations

A simple method for estimating viability of dry yeast inocula and the initial kinetic parameters, μm (h−1) and νm (h−1), for batch fermentations was developed based on broth assays during the exponential growth phase. Ethanol concentrations of shake-flask broths, determined by assay or calculated from mass loss, were fitted with an exponential growth/production equation as a model. Medium (400 ml, 200 g l−1 sucrose) was inoculated with commercial dry yeast products (Saccharomyces cerevisiae) and fermented at 25°C. Some were presaturated with CO2 for mass loss measurements. A lag period of approximately 15 min was observed before the yeast started producing ethanol. Initial kinetic parameters were similar to published values.

Rolling-sphere viscometer for In situ monitoring of shake-flask fermentations

Abstract A rolling-sphere viscometer (RSV) was constructed and evaluated for monitoring apparent viscosities of fermentation broths in shake flasks or test tubes. The apparatus was calibrated by measuring translational velocities of magnetic stainless steel spheres (0.16–0.95 cm diameter) rolling in Newtonian viscosity standards (50–12,500 mPa·s) on surfaces inclined 20° to 70°. The method was applied to fermentation broths of Aureobasidium pullulans. Apparent viscosities fit the power-law equation. Maximum viscosities and minimum power-law indices were reached within 4 to 6 days fermentation time, followed by a decrease in viscosity.

Continuous estimation of viscosity, fluid density, surface tension, and heat output during fermentations

Currently, sensors for measuring fluid density, surface tension, viscosity, and heat output are rarely if ever used in estimating conditions continuously in microbial cultures. Measurement of fluid density and surface tension can be accomplished with differential air pressure-based sensors. Fluid viscosity can be estimated by measuring differential fluid pressures. These three sensors, as tested with cultures, were comprised of glass and rubber tubing, a gas supply for density and surface tension and a peristaltic pump for viscosity. The heat output was estimated with an infrared detector spaced two inches from the bottom surface of a solid-state culture flask.