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Biomedical subjects

R D Tanner

Publications and source records attributed to R D Tanner.

11 recordsLinked to original sources
PubMed1991

The production of extracellular and intracellular free amino acids during aerated fermentation of glucose by baker's yeast (Saccharomyces cerevisiae).

During a study of the effects of a high level of NaCl on the content of free intracellular amino acids in baker's yeast grown in aerated fermentation of glucose it was found (Malaney et al. 1988, 1989; Malaney and Tanner 1988) that 0.6 mol/L exogenous NaCl significantly increased the content of free intracellular citrulline, glutamine, ornithine, arginine and lysine (all basic amino acids) over that observed at zero mol/L exogenous NaCl. (Exogenous is defined as salt added beyond that present in the mineral salts in the culture medium.) This paper describes the production and relative relationships of both extracellular and free intracellular amino acids by S. cerevisiae under conditions of high NaCl content in the growth medium at pH 5 and 32 degrees C. For early culture times (6 h), the production of glutamine, citrulline, valine, isoleucine, ornithine, lysine and histidine were all enhanced by the addition of NaCl. For late times (24 h), except for ornithine, the early-time-enhanced amino acids continued to be enhanced by the addition of NaCl. In addition, the yields of several other amino acids also were increased by exogenous salt at this late time. These include aspartic acid, threonine, glutamic acid, cystine, methionine, tyrosine, phenylalanine and arginine.

Aerobiosis↗
PubMed1988

Semisolid state fermentation of baker's yeast in an air-fluidized bed fermentor.

In an attempt to grow microorganisms other than fungi using a solid-state fermentation process, a model system of Baker's yeast (Saccharomyces cerevisiae) was cultured in an air-fluidized bed fermentor. A semisolid potato mixture (pretreated with alpha-amylase) was used for the substrate in this highly aerated system. The growth of Baker's yeast in this air-fluidized bed process was easily controllable and very reproducible. Once feasible moisture levels and air flow rates were determined, the independent variables studied were the amount of the enzyme used for digesting the potato starch, the size of the yeast inoculum, and the concentration of the added defined medium.

Culture Media↗
PubMed1986

Relating damped oscillations to sustained limit cycles describing real and ideal batch fermentation processes.

A batch fermentation model is presented in which the specific growth rate and yield functions are chosen such that sustained oscillations in both the cell and substrate concentration occur. This phenomenon is shown to be a Hopf bifurcation in the underlying system of non-linear ordinary differential equations which comprises the model. It is shown that for oscillations in the substrate concentration to occur it is necessary for the yield term to depend on both the cell and substrate levels.

Cell Count↗
PubMed1984

The impedance method for monitoring total coliforms in wastewaters. Part II. Results and evaluation.

An impedance technique is presented as a method which offers promise as a test for estimating the numbers of total coliform bacteria in wastewaters. The technique reported here has the advantage of being 3-4 times faster than the standard membrane filter method (i.e. 4-7 h, compared with 20-24 h). The technique shows the disadvantages of (a) being markedly higher in initial cost of instrumentation, (b) being somewhat more expensive in required supplies, and (c) giving results which deviate considerably from the values given by the MF method. A parallel use of the impedance and MF methods when both speed and accuracy are desired may be an appropriate practical compromise.

Bacteriological Techniques↗
PubMed1981

Inherent limitations to the problem of reducing the lysine microbiological assay time.

A kinetic approach is proposed to shorten the microbiological assay time for the determination of unbound L-lysine. The present lysine bacterial assay takes from 16 to 24 h using Pediococcus cerevisiae P-60 ATCC 8042 (formerly Leuconostoc mesenteroides P-60 ATCC 8042) and uses a medium in which lysine is the limiting substance. Measurements of the final cell concentration are linearly correlated with the initial concentration of lysine, S, to provide an indirect estimate of S. We propose to understand the limitations inherent to the reduction of the assay time to 4 h by focusing in our analysis on the bacterial late lag or early growth transient phases, rather than the stationary phase of growth. Generally, the Monod equation is expected to describe a hyperbolically increasing correlation between the bacterial specific growth rate at about 2-4 h and the initial lysine concentration. A hyperbolic correlation is obtained by 3 h, but the lysine region of interest falls in the saturated portion of the curve. Discriminations between different initial lysine levels are therefore difficult with this nearly flat curve. On the other hand, when the initial inoculum level is lowered, so that substrate inhibition becomes effective, a correlation with a large negative slope is obtained by 4 h. Limitations to using absorbance measurements for the rapid assay turn up in a lack of reproducibility and, hence, a large variance associated with the measurements. Alternative microbial measuring techniques, such as impedance methods, need to be examined in order to reduce that large variance.

Biological Assay↗
PubMed1977

A fermentation process for producing both ethanol and lysine-enriched yeast.

In 18 batch-fermentation experiments, baker's yeast was grown in an enriched mineral medium, containing 10% by weight glucose, at various pH and temperature levels. The pH and temperature are just two representative engineering variables which can be easily varied at negligible cost. The commercial yeast inoculum, 20% by weight or about .16% viable cells, was selected to represent industrial (nonsterile) conditions. Free L-lysine, ethanol, and cell growth were followed in time for each batch run held at a fixed pH and temperature. The maximum free lysine level reached at either 10 1/2 or 24 hr occurred at a pH of 5 and 32 degrees C. At 24 hr, the peak free lysine level, 120 mg/liter, is three times as great as the uncontrolled pH counterpart. In terms of total L-lysine (free plus protein-bound) the peak represents a 25% improvement over the uncontrolled case, based on an average 3.5% lysine level per cell weight. The greatest measured cell level, .9% by weight in the fermentation broth, or a 5 1/2-fold increase over th inoculum, was reached during the 36 degrees C and pH 3 run, while the largest measured ethanol value (3%, or 30% conversion by weight from glucose) was achieved during the 28 degrees C and pH 6 experiment. The optimal lysine run product, however, no less than 15% of the maximum cell and 30% of the maximum ethanol levels.

Ethanol↗
PubMedDate not supplied

In situ bubble fractionation strategies for separating individual proteins in a batch baker's yeast fermentation process.

Extracellular proteins produced by yeast have been observed to stratify in the extracellular fluid of a batch bioreactor, thus creating a vertical concentration gradient. We observed that, in the four different experiments conducted, each varied in their protein recovery characteristics. For example, sparging the system with gas accentuates the separation, though even in a nonsparged system, the in situ generation of minute carbon dioxide bubbles by yeast cells creates a protein gradient as the bubbles carry proteins upward. Based on these and other observations, we propose possible strategies for recovering the individual proteins from a system containing the four major proteins considered. A simple steady-state mathematical model, based on convective upward protein transport being balanced by downward protein diffusion, has been used to describe the behavior of each of these four extracellular proteins in the fermentation broth.

Fermentation↗