Application of the response surface methodology for optimizing the activity of an aprE -driven gene expression system in Bacillus subtilis

Abstract

The major targets for improvement of recombinant expression systems in microbial cells are gene dosage, transcriptional control machinery and, to some extent, translation. Here we show that optimization of fermentation conditions by applying statistically designed, multifactorial experiments offers an additional method for potential enhancement of gene expression systems. A chromosomally encoded fusion between the Bacillus subtilis aprE regulatory region and the E. coli lacZ gene carried by the B. subtilis host cells was used. The 2 x SG sporulation medium was used as a basal medium. Among the 11 fermentation factors we examined, the most significant variables influencing beta-galactosidase expression were statistically elucidated for optimization and included peptone, MgSO4.7H2O, and KCl. The optimum concentrations of these variables were predicted by using a second-order polynomial model fitted to the results obtained by applying the Box-Behnken design, a response surface method. Calculated optimum concentrations were predicted to confer a maximum yield of 2,423.5 beta-galactosidase specific activity units. A verification experiment performed under optimal conditions yielded 96% of the predicted specific activity value with an increase by a factor of almost 5 compared with the results obtained under basal conditions.

Biodegradation of crude petroleum oil and environmental pollutants by Candida tropicalis strain

“…However, the addition of yeast extract to the medium enhanced the biodegradation capacity. This could be due to the fact that yeast extract was enriched with amino acids and vitamins which acted as co-factors for enzyme productions (El-Helow et al, 2000;Pedersen and Nielsen, 2000;Konsoula et al, 2004). The cellular morphology of the yeast strain A was examined under SEM, when grown in three different media: Malt-peptone medium as a complex medium without adding petroleum oil (M6), NSW+ 1% petroleum oil (M2) and NSW supplemented with glucose and yeast extract amended with 0.5% crude petroleum oil (M5).…”

Microalgae cultivation in air‐lift reactors: Modeling biomass yield and growth rate as a function of mixing frequency

“…A statistical model describing the effect of light fraction and cycle time is proposed. An empirical model was preferred to a theoretical model because it allows the study of a wide range of mixing frequencies (and thus light gradient/dark cycles) and it is an established method to study main effects and two-factor interactions with relatively few experimental trials (El Helow and Abdel-Fattah, 2000;Hwang and Hansen, 1997). The development of a theoretical model would require extensive knowledge on the metabolism response to different light gradient/dark cycles, which is not available yet.…”

Isolation and characterization of a haloalkaliphilic protease producer bacterium from Wadi Natrun in Egypt

“…Nevertheless, cells can be environmentally programmed to express certain valuable postexponential secondary metabolites rather than others (El-Helow et al, 2000). The main purpose of the second part of this work was to find out a culture condition that shifts the metabolic activity of NA7 cells towards more expression of alkaline protease.…”