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.

Influence of Culture Conditions on the Fatty Acid Profiles of Laboratory-Adapted and Freshly Isolated Strains of Helicobacter pylori

Abstract: Cellular fatty acids of Helicobacter pylori have taxonomic, physiological, and pathogenic implications. However, little is known about the fatty acid composition under various culture conditions. H. pylori is usually grown on blood-supplemented complex media, and the fatty acids in the blood may affect the fatty acids in the cells. In addition, frequently subcultivated laboratory-adapted strains may have properties different from those of fresh clinical isolates, which are culturable only for a limited number of passages. Therefore, the cellular fatty acid profiles of laboratory-adapted strains (LAS) and freshly isolated strains (FIS) were compared after growth on agar that was fatty acid free and growth on blood agar that contained fatty acids. LAS ATCC 43504, 51932, and 700392 and the FIS IMMi 88, 89, and 92, each with <10 subcultures, were cultured in parallel on a fatty acid-free agar (ISAF) and on 5% sheep blood agar (SBA), which contained oleic acid (18:1 9c), hexadecanoic acid (16:0), and octadecanoic acid (18:0). ISAF-grown cultures showed no 18:1 9c and no appreciable differences between the profiles of FIS and LAS. After culture on SBA, the strains showed 18:1 9c and increased 16:0 and 18:0 content combined with decreased tetradecanoic acid (14:0) content compared to ISAF-grown cells. The changes in the fatty acid profiles were much more pronounced in FIS than in LAS. LAS are obviously characterized by a lower uptake of the fatty acids from the growth medium than FIS. Furthermore, it could be shown that this LAS behavior is most likely a primary strain attribute that is favored under laboratory conditions. The pronounced uptake of fatty acids by strains with FIS behavior may be associated with the expression of virulence properties.

Optimization of growth medium and fermentation conditions for improved antibiotic activity of Xenorhabdus nematophila TB using a statistical approach

Abstract: A sequential optimization approach based on statistical experimental designs was employed to optimize growth medium and fermentation conditions, in order to improve the antibiotic activity of Xenorhabdus nematophila TB. Tryptone soyptone broth (TSB) was chosen as the original medium for optimization. Glucose and peptone were identified as the optimum carbon and nitrogen sources using single factor method. Peptone, fermentation time, initial pH and inoculum volume were identified as the critical factors which highly influenced the antibiotic activity of X. nematophila TB using Plackett–Burman (PB) design. The critical factors were subsequently optimized to locate their optimum domain using steepest ascent method and were further optimized using central composite design (CCD), involving response surface methodology (RSM). The optimum growth medium and fermentation conditions for antibiotic production by X. nematophila TB consisted of glucose 5.00 g/l, peptone 25.6 g/l, NaCl 5.00 g/l, K2HPO4 2.50 g/l, initial pH 7.59, medium volume (100/250 ml), inoculation age (OD600 nm: 2.00), inoculum volume 9.95%, rotary speed 150 rpm, temperature 25°C and fermentation time 54.1 h. An overall of 73.52% increase in antibiotic activity (418.7 U/ml) was obtained as compared with the unoptimized conditions (241.3 U/ml). This study provides a powerful tool to optimize the bioprocess of the antibiotic production by X. nematophila TB. Key words: Xenorhabdus nematophila, antibiotic activity, growth medium, fermentation conditions, optimization, response surface methodology.

Control of Fatty‐Acid Synthetase Levels by Exogeneous Long‐Chain Fatty Acids in the Yeasts Candida lipolytica and Saccharomyces cerevisiae

Abstract: Endogeneous fatty acid biosynthesis in the two yeast species, Saccharomyces cerevisiae and Candida lipolytica is completely repressed by the addition of long-chain fatty acids to the growth medium. In Candida lipolytica, this repression is accompanied by a corresponding loss of fatty acid synthetase activity in the cell homogenate, when the cells were grown on fatty acids as the sole carbon source. The activity of the Saccharomyces cerevisiae fatty acid synthetase, however, remains unaffected by the addition of fatty acids to a glucose-containing growth medium. From fattyacid-grown Candida lipolytica cells no fatty acid synthetase complex can be isolated, nor is there any immunologically cross-reacting fatty acid synthetase protein detectable in the crude cell extract. From this it is concluded that Candida lipolytica, but not Saccharomyces cerevisiae, is able to adapt to the growth on fatty acids either by repression of fatty acid synthetase biosynthesis or by a fatty-acid-induced proteolytic degradation of the multienzyme complex. Similarly, the fatty acid synthetase complex disappears rapidly from stationary phase Candida lipolytica cells even after growth in fatty-acid-free medium. Finally, it was found that the fatty acid synthetase complexes from Saccharomyces cerevisiae and Candida lipolytica, though very similar in size and subunit composition, were immunologically different and had no common antigenic determinants.