Growth medium

About: Growth medium is a research topic. Over the lifetime, 1889 publications have been published within this topic receiving 59171 citations. The topic is also known as: culture medium & culture media.

The failure of phenol treated escherichia coli to grow on membrane filters

Abstract: SUMMARY: Counts of Escherichia coli were done on nutrient agar (control), on membrane filters on nutrient agar and on membrane filters on filter paper pads. With untreated bacteria counts were similar under all conditions, though membrane filters on nutrient agar tended to give slightly low counts. Phenol treated bacteria gave much lower counts when membrane filters were used: the mean counts for 3 strains of the test organism with filters on nutrient agar varied from 35–65% of the control, while counts with filters on filter paper pads were somewhat lower, varying from 30–47% of the control. The low counts on membrane filters on filter paper pads were not due to adsorption of phenol by the filters or to a low concentration of nutrients in the growth medium.

Production and Partial Characterization of Lipase from Pseudomonas putida

Abstract: The production of lipase from Pseudomonas putida 922 was optimized by modifying various physical parameters such as carbon source, nitrogen source, pH, salt concentration and biochemical parameters of the production medium such as temperature and incubation time of the growth medium. Oil cakes were also used as carbon source to check for an increased production of the enzyme. The bacterium was found to have a maximal growth at pH 10 with the enzyme production being highest (24 U/ml) after 48 hours at 30°C and pH 10. The optimum composition of the medium was mustard oil cake as carbon source, yeast extract or peptone as nitrogen source and 1% sodium chloride concentration. Partial characterization of the enzyme was carried out where the optimum working pH and temperature was found to be 10 and 40oC, respectively. Enzyme stability was found to lie in the pH and temperature ranges of 5-11 and 30-40oC, respectively. Partial purification of the enzyme was carried out at 80% ammonium sulphate saturation. Molecular mass of lipase was determined by SDS PAGE and found to be 45 kDa.

Production of recombinant protein by a novel oxygen-induced system in Escherichia coli.

Abstract: The SoxRS regulon of E. coli is activated in response to elevated dissolved oxygen concentration likely to protect the bacteria from possible oxygen damage. The soxS expression can be increased up to 16 fold, making it a possible candidate for recombinant protein expression. Compared with the existing induction approaches, oxygen induction is advantageous because it does not involve addition or depletion of growth factors or nutrients, addition of chemical inducers or temperature changes that can affect growth and metabolism of the producing bacteria. It also does not affect the composition of the growth medium simplifying the recovery and purification processes. The soxS promoter was cloned into the commercial pGFPmut3.1 plasmid creating pAB49, an expression vector that can be induced by increasing oxygen concentration. The efficiency and the regulatory properties of the soxS promoter were characterized by measuring the GFP expression when the culture dissolved oxygen concentration was increased from 30% to 300% air saturation. The expression level of recombinant GFP was proportional to the oxygen concentration, demonstrating that pAB49 is a controllable expression vector. A possible harmful effect of elevated oxygen concentration on the recombinant product was found to be negligible by determining the protein-carbonyl content and its specific fluorescence. By performing high density growth in modified LB medium, the cells were induced by increasing the oxygen concentration. After 3 hours at 300% air saturation, GFP fluorescence reached 109000 FU (494 mg of GFP/L), representing 3.4% of total protein, and the cell concentration reached 29.1 g/L (DW). Induction of recombinant protein expression by increasing the dissolved oxygen concentration was found to be a simple and efficient alternative expression strategy that excludes the use of chemical, nutrient or thermal inducers that have a potential negative effect on cell growth or the product recovery.

Intracellular and extracellular amino acid pools of the marine diatom phaeodactylum tricornutum (bacillariophyceae) grown on unenriched seawater in high‐cell‐density dialysis culture1

Abstract: The consumption of inorganic macronutrients (NO3−+ NO2−, NH4+, and PO4−3) and the composition of intra- and extracellular dissolved free amino acid pools (IDFAA and EDFAA, respectively) were determined in continuous-reservoir batch dialysis cultures of the marine diatom Phaeodactylum tricornutum Bohlin maintained on unenriched natural seawater as a growth medium. Nutrient diffusion (Nd), which equals the nutrient uptake of the culture, increased with the cell density and the age of the culture. A concentration of 6.77 × 107 cells · mL−1 was obtained in stationary phase, which coincided with the NO3−+ NO2− diffusion limit (Ndmax) of the dialysis apparatus. The Ndmax for NH4+ occurred much earlier, at the end of exponential growth, whereas Ndmax for PO4−3 was not attained during the growth cycle of the culture, even in early stationary phase. A significant depletion (77%) of the IDFAA pool during exponential phase was followed by a reestablishment–to approximately 60% of the initial level–of internal pools during linear and stationary growth phases. This recovery occurred during the illuminated portion of the photoperiod (12:12 h LD) and involved principally the amino acids GLN, GLU, β-GLU, and ASN. The recovery of GLN and ASN levels was particularly significant, because the intracellular concentrations of these amino acids were higher at the end of the growth cycle than before. The EDFAA pool was generally dominated by the amino acids SER and GLY+THR; however, during active growth, ORN and LYS often constituted an important fraction. The EDFAA concentration increased until linear growth phase was reached, during which a higher concentration of total free amino acids was attained in darkness than under illumination. The EDFAA component diminished afterward, and in stationary phase this fraction returned to concentrations equivalent to those observed at the beginning of the growth cycle. The variations in EDFAA concentrations were expressed by a pronounced decrease in the cellular excretion of amino acids with increasing cell density. These cellular responses of Phaeodactylum tricornutum in dense culture, specifically the regulation of amino acid excretion and intracellular pool size, may affect the N-conversion coefficient (YN). Consequently, by prolonging the linear phase of growth and reducing the concentration of autoinhibitory metabolites by diffusion, a markedly enhanced final cell density can be achieved in cultures grown on natural unenriched seawater.

Stimulation of the growth of microorganisms

Abstract: PROCESS FOR STIMULATING THE GROWTH OF MICROORGANISMS BY EMPLOYING AN EFFECTIVE AMOUNT OF DIMETHYL SULFOXIDE IN THE GROWTH MEDIUM.