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.

Induction of D-amino-acid oxidase by D-alanine in Rhodotorula gracilis grown in defined medium

Abstract: SUMMARY: The obligate aerobe yeast Rhodotorula gracilis was grown in batch culture on a chemically defined, pH-controlled medium containing glucose or d-alanine as carbon sources, ammonium or d-alanine as nitrogen sources, and d-alanine as a sole carbon and nitrogen source. Under these conditions, d-alanine induced the synthesis of d-amino-acid oxidase (EC 1.4.3.3) to an extent depending on the nutrients, the highest specific activity of the enzyme [up to 0.6 U (mg protein)−1] being detected when both d-alanine and glucose were present in the growth medium. In contrast, enzyme activity was negligible when both ammonium and glucose were present in the growth medium, even in the presence of d-alanine. The racemic mixture dl-alanine was also utilized as a source of both carbon and nitrogen for the growth of R. gracilis, but the enzyme activity appeared only after the depletion of l-alanine from the medium. Data on transmembrane transport of d-alanine in the presence of different nutrients clearly indicated that the l-isomer prevented induction by d-alanine through inhibition of the transport of the d-amino acid into cells. However, such an effect was not exerted by ammonium, indicating that this compound probably acts at the level of enzyme synthesis.

GlaA Promoter Controlled Production of a Mutant Green Fluorescent Protein (S65T) by Recombinant Aspergillus niger during Growth on Defined Medium in Batch and Fed-Batch Cultures

Abstract: The first successful expression of the Aequorea victoria green fluorescent protein (GFP) gene in Aspergillus niger is described. When the wild-type GFP gene was expressed in A. niger, neither the fluorescence nor the full translation product of the wtGFP gene was detectable. However, the expression of a mutant form of the green fluorescent protein (S65TGFP) gene resulted in the formation of a functional fluorescent polypeptide. The synthesis of S65TGFP was used to study glaA promoter controlled heterologous gene expression by recombinant A. niger in batch and fed-batch cultures using a defined growth medium. Cells were grown on xylose as noninducing carbon source, and the production of S65TGFP was accomplished by the addition of maltose. The recombinant protein accumulated up to 10 or 25 mg of S65TGFP g-1 cell dry weight using either a maltose pulse for induction or continuous addition of the inducing carbon source, respectively. Irrespective of the induction protocol, the recombinant protein started to accumulate 2 h after addition of the inducing carbon source and reached its maximum specific concentration 10 h after induction. Bright green fluorescing fungal pellets were first detectable by fluorescence microscopy 4-5 h after the onset of maltose addition.

Enrichment, isolation and counting of soil microorganisms

Abstract: Publisher Summary The chapter discusses enrichment, isolation, and counting of soil microorganisms. A great number of morphological and physiological types of microorganisms can be found in soils. Enrichment and isolation of soil microorganisms are based on the cultivation of these microorganisms in liquid or agar media. To obtain anaerobic growth conditions for facultative anaerobes, it is sufficient to prevent the oxygen diffusion in the growth medium. This can be achieved by slowly passing a high-purity gas over a hot column. If necessary, clean the gas further by passing it over a cold catalyst or Oxisorb. The isolation of strictly anaerobic bacteria by plating methods poses special problems. Cellulose is mainly degraded by fungi in soils. In contrast, most bacteria can only be cultivated on partially hydrolyzed cellulose. Pseudomonaceae are gram-negative bacteria that are found in soil, water, and air. Oligotrophic bacteria include taxonomically and physiologically different microbial groups. Until the early 1970s, the classical concept of aerobic diazotrophs—that is, bacteria able to use molecular nitrogen (N 2 ) as their sole nitrogen source for growth—referred only to bacteria able to grow under atmospheric oxygen concentrations. Soils and water may contain up to 10 8 –10 12 bacterial cells per gram of soil or milliliter of water, if determined by microscopic techniques. Since 1970, epifluorescence microscopy has become the major technique for direct enumeration of bacteria and fungi in soil. Cyanobacteria are prokaryotic microorganisms containing chlorophyll a and producing oxygen as a by-product of their photosynthetic activity. Cultures of cyanobacteria can be preserved after growth and should not be maintained in refrigerator-like other prokaryotes.

Time-dependent profiling of metabolites from Snf1 mutant and wild type yeast cells

Abstract: The effect of sampling time in the context of growth conditions on a dynamic metabolic system was investigated in order to assess to what extent a single sampling time may be sufficient for general application, as well as to determine if useful kinetic information could be obtained. A wild type yeast strain (W) was compared to a snf1Δ mutant yeast strain (S) grown in high-glucose medium (R) and in low-glucose medium containing ethanol (DR). Under these growth conditions, different metabolic pathways for utilizing the different carbon sources are expected to be active. Thus, changes in metabolite levels relating to the carbon source in the growth medium were anticipated. Furthermore, the Snf1 protein kinase complex is required to adapt cellular metabolism from fermentative R conditions to oxidative DR conditions. So, differences in intracellular metabolite levels between the W and S yeast strains were also anticipated. Cell extracts were collected at four time points (0.5, 2, 4, 6 h) after shifting half of...

Recombinant protein expression in Lactococcus lactis using the P170 expression system

Abstract: The use of the Gram-positive bacterium Lactococcus lactis in recombinant protein production has several advantages, including the organism's long history of safe use in food production and the fact that it does not produce endotoxins. Furthermore the current non-dairy L. lactis production strains contain few proteases and can secrete stable recombinant protein to the growth medium. The P170 expression system used for recombinant protein production in L. lactis utilizes an inducible promoter, P170, which is up-regulated as lactate accumulates in the growth medium. We have optimised the components of the expression system, including improved promoter strength, signal peptides and isolation of production strains with increased productivity. Recombinant proteins are produced in a growth medium with no animal-derived components as a simple batch fermentation requiring minimal process control. The accumulation of lactate in the growth medium does, however, inhibit growth and limits the yield from batch and fed-batch processes. We therefore combined the P170 expression system with the REED™ technology, which allows control of lactate concentration by electro-dialysis during fermentation. Using this combination, production of the Staphylococcus aureus nuclease reached 2.5 g L(-1).