Teaching the fundamentals of experimental design

The effects of temperature (20°, 25°, 30° C), pH (7.5, 8.0, 8.5) and dissolved oxygen (40%, 45%, 50%, 55%, 60% of concentration in air-saturated medium) on the growth of Brevibacterium linens were studied with cultures on sodium l-lactate and casamino acids in a regulated fermentor, using a factorial design methodology and an analysis of variance programme. The effect on growth rates was very striking: an extremely significant quadratic effect of oxygen, a marked negative effect of pH and a great negative interaction between pH and temperature were observed. Growth, transition from cocci to rods and pigmentation were inhibited by dissolved oxygen levels of 40% and 60%, while the level 50% produced higher absorbance values and growth rates.

Influence of temperature, pH and dissolved oxygen on growth of Brevibacterium linens in a fermentor

Mathematical methods of experiment design have so far found little use in the optimization of microbiological processes. The conventional optimization procedure is still the transformation of functional relationship ofn variables into n unidimensional optimizations; furthermore, the Bos-Wilson gradient method is often used. This paper presents a review of methods used in other fields, and their application in microbiological practice. The methods are classified according to whether they require, besides the simple determination of the objective function (direct search methods), also the finding of its first (gradient methods) or second derivative (Newton-Raphson method). A modified Rosenbrock’s method of direot optimum search and the gradient Box-Wilson method were used in parallel for the optimization of yeast growth on methanol. Their comparison showed that Bosenbrock’s method is more suitable for multiparameter systems.

Application of mathematical optimization methods in microbiology

Mass spectrometry is a versatile technique that is used for the determination of elements at the trace and ultratrace level along with the isotope ratios. The accuracy in the quantification of isotope ratios of radionuclides is essential for environmental monitoring, migration studies, dating, determination of burn-up of fuel, nuclear material accounting and radioactive waste control. Inductively coupled plasma mass spectrometry (ICP-MS) is advantageous due to its outstanding sensitivity, precision and good accuracy for isotope ratio measurements and enhanced figures of merit for the determination of isotope ratio measurements. These advantages can be enhanced by various other variations of ICP-MS like the use of a multiple ion collector device (MC-ICP-MS). The review gives an idea of the various applications in the nuclear field and touches upon some of the important elements used in nuclear industry.

Mass Spectrometry: A Boon to Nuclear Industry

Whole cells of Mucor inaequisporus were used for biotransformation of the flavonoid naringin, as a green method for structural diversification of this class of natural product. The metabolism of the fungus was challenged against naringin under several culturing conditions, using statistical optimization. Eight parameters were evaluated comprising type and concentration of carbon source, substrate concentration, substrate addition time, shaking, luminosity, temperature and extraction time. Sixteen different culture conditions were tested in this screening. After LC-MS analysis, several biotransformation products were identified and naringenin was identified as the major product. Eleven biotransformation products were detected in Ft-HRMS analyses and identified as naringenin as major compound, 4’-methoxynaringenin, 4’-methoxynaringin, rhoifolin, apigenin, methoxyapigenin, acetylated naringin, and also two biflavonoids and two triflavonoids. Ft-HRMSn showed to be a powerful technique for structural elucidation of flavonoid biotransformation products. The fungus was capable to perform deglycosylation, reduction and O-methylation reactions at this substrate indicating good enzymatic potential, since these reactions weren’t observed before for this fungus-genus.

Enzymatic Potential of Mucor inaequisporus for Naringin Biotransformation, Accessed by Fractional Factorial Design and Mass Spectrometry Analysis

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.

Bioconversion from DL-Homoserine to L-Threonine

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.

Bioconversion from DL-Homoserine to L-Threonine: I. Application of factorial designs

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Bioconversion from DL-Homoserine to L-Threonine

Bioconversion from DL-Homoserine to L-Threonine: I. Application of factorial designs