In order to understand the metabolism of a microorganism, it is important to determine its minimal nutrient requirements. Moreover, defined media are less sensitive to sterilization conditions, typically highly soluble and give consistent results at various scales. A chemically defined medium leads to a more reproducible fermentation performance, which is an important and desired characteristic for any industrial fermentation process. īecause of these disadvantages, there is a need for chemically defined media. Furthermore, a consistent product quality is extremely difficult to ensure. As a result of inevitable lot-to-lot variability, the composition of yeast extract can vary widely leading to inconsistent process stability and performance. Even though complex media continue to dominate the fermentation industry due to their lower costs and faster cell growth, there are also major drawbacks for their application. It contains a mixture of carbohydrates, amino acids, peptides, vitamins, trace elements and various other oligomeric compounds. Especially yeast extract is one of the most frequently used complex supplements. yeast extract, peptone, meat extract and casein or soy bean hydrolysates. For this reason, chemically undefined media containing complex components of natural origin are often applied. The majority of fastidious microorganisms require miscellaneous trace elements, vitamins and amino acids, which are usually not included in standard mineral media. This approach facilitates media development, strain characterization and cultivation of fastidious microorganisms in chemically defined minimal media while simultaneously reducing the experimental effort.Īs the nutritional requirements of different microorganisms vary, the composition of culture media have to be adapted accordingly. By combining a systematic combinatorial approach based on monitoring the respiration activity with cultivation in microtiter plates, high throughput experiments with high information content can be conducted. However, the method is generally suitable for a wide range of microorganisms. pumilus DSM 18097 was chosen as a model organism to demonstrate the method. The introduced method allows an efficient and rapid identification of unknown auxotrophic deficiencies and can be used to develop a simple chemically defined tailor-made medium. Experiments have shown that the investigated strain requires amino acids, especially cysteine or histidine and the vitamin biotin for growth. By monitoring of the respiration activity, nutrients were supplemented to and omitted from the rich chemically defined medium in a rational way, thus enabling a systematic and fast determination of the auxotrophic deficiencies. The strain was successfully cultivated in this medium. Therefore, a rich chemically defined minimal medium was tested containing basically all vitamins, amino acids and nucleobases, which are essential ingredients of complex components. Resultsīacillus pumilus DSM 18097 was unable to grow in a mineral medium without the addition of complex compounds. In this study, a respiration activity monitoring system for shake flasks and its recent version for microtiter plates were used to clarify unknown auxotrophic deficiencies in the model organism Bacillus pumilus DSM 18097. Culturing bacteria with unknown auxotrophies in chemically defined media is challenging and often not possible without an extensive trial-and-error approach. This concept results in better reproducibility, it simplifies downstream processing of secreted products and enable rapid scale-up. Therefore, the use of chemically defined media receives more and more attention in commercial fermentations. The chemical composition of the complex compounds is prone to significant variations from batch to batch and quality control is difficult. Culture media containing complex compounds like yeast extract or peptone show numerous disadvantages.
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