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.

Effects of pCO2 on the growth and metabolism of Clostridium sporogenes NCIB 8053 in defined media

Abstract: The effects of the partial pressure of carbon dioxide (pCO2) on the growth rate of Clostridium sporogenes NCIB 8053 in batch culture were investigated in defined minimal media. Depending upon the growth medium, CO2 was stimulatory or inhibitory to growth. The absolute CO2 requirement for growth displayed by Cl. sporogenes in certain media was shown to be due to the involvement of CO2 in the synthesis of branched-chain amino acids. High concentrations of CO2 were growth inhibitory except in complex media. In media where an optimal pCO2 was observed it was approximately 0˙45 atm. The pattern of fermentation end-products displayed by this organism was also modified by the pCO2. The equilibria of the different species of ‘CO2’ present in microbiological media are described. Finally, the metabolic control theory of Kacser, Burns, Heinrich and Rapoport has been applied to the results obtained, to provide a quantitative description of the effects of pCO2 on the growth rate of Cl. sporogenes.

Formation of D-amino-acid oxidase in the yeast Trigonopsis variabilis

Abstract: Production of D-amino-acid oxidase by Trigonopsis variabilis has been investigated using a two-stage cultivation technique. After transfer of exponentially growing cells to fresh medium, the enzyme was induced by addition of D-amino acids to the growth medium, among which D-methionine and D-alanine were the most effective. The simultaneous presence of the L form of amino acids or did not affect this induction. The presence of trace metals, inorganic phosphate, and a high rate of agitation were necessary for formation of maximal D-amino-acid oxidase activity. The enzyme is not subject to glucose repression.

Redox engineering by ectopic expression of glutamate dehydrogenase genes links NADPH availability and NADH oxidation with cold growth in Saccharomyces cerevisiae.

Abstract: Background: Cold stress reduces microbial growth and metabolism being relevant in industrial processes like wine making and brewing. Knowledge on the cold transcriptional response of Saccharomyces cerevisiae suggests the need of a proper redox balance. Nevertheless, there are no direct evidence of the links between NAD(P) levels and cold growth and how engineering of enzymatic reactions requiring NAD(P) may be used to modify the performance of industrial strains at low temperature. Results: Recombinant strains of S. cerevisiae modified for increased NADPH ‑ and NADH‑dependent Gdh1 and Gdh2 activity were tested for growth at low temperature. A high‑copy number of the GDH2‑encoded glutamate dehydro‑ genase gene stimulated growth at 15°C, while overexpression of GDH1 had detrimental effects, a difference likely caused by cofactor preferences. Indeed, neither the Trp − character of the tested strains, which could affect the syn‑ thesis of NAD(P), nor changes in oxidative stress susceptibility by overexpression of GDH1 and GDH2 account for the observed phenotypes. However, increased or reduced NADPH availability by knock‑out or overexpression of GRE3, the NADPH‑dependent aldose reductase gene, eliminated or exacerbated the cold‑growth defect observed in YEpGDH1 cells. We also demonstrated that decreased capacity of glycerol production impairs growth at 15 but not at 30°C and that 15°C‑grown baker’s yeast cells display higher fermentative capacity than those cultivated at 30°C. Thus, increasing NADH oxidation by overexpression of GDH2 would help to avoid perturbations in the redox metabolism induced by a higher fermentative/oxidative balance at low temperature. Finally, it is shown that overexpression of GDH2 increases notably the cold growth in the wine yeast strain QA23 in both standard growth medium and synthetic grape must. Conclusions: Redox constraints limit the growth of S. cerevisiae at temperatures below the optimal. An adequate supply of NAD(P) precursors as well as a proper level of reducing equivalents in the form of NADPH are required for cold growth. However, a major limitation is the increased need of oxidation of NADH to NAD + at low temperature. In this scenario, our results identify the ammonium assimilation pathway as a target for the genetic improvement of cold growth in industrial strains.

Growth limitation in hybridoma cell cultures: the role of inhibitory or toxic metabolites.

Abstract: Hybridoma cells usually grow to fairly low cell densities in batch cultures (1–3×106 cells/ml). The reason for this is either that essential nutritional components of the medium are consumed, or that the cells produce some kind of inhibitory or toxic metabolite. This investigation presents evidence for the latter. Spent medium from cultures of hybridoma cells did not support growth of cells at lower cell densities (1–3×105 cells/ml). The ability to support cell growth could not be restored by adding additional serum, energy sources (glucose, pyruvate) or L-glutamine. Furthermore, the consumption of amino acids could not account for this growth inhibition. On the contrary, the spent medium contained a substance that inhibited cell growth. This substance or metabolite was found in a fraction eluted from a gel filtration column when spent medium was applied to the column. This substance was found in the spent medium from all hybridoma and myeloma cell lines that were tested. The molecular weight of the substance was about 5 kD. Spent medium from two hybridoma cell lines also contained a substance that was eluted in the same fraction as albumin (67 kD). It is likely that this (or these) substance(s) is responsible for the growth limitation in hybridoma cell cultures.