Microbial culture

The bacteria s spatial juxtaposition (awareness relative to other bacteria) may also be hindered by turbulence. In the worst-case scenario, the bacteria are not able to make significant contact and are not able to achieve the necessary cell density for optimal operation (Bliem and Katinger, 1988b) or are not able to make syntropic relationships with other bacterial cultures (Hoffmann et al., 2008). The result is that start-up performance is very poor with minimal or insignificant conversion while long-term performance is not hindered in a bacterial mixture that allows competition and has at least one shear-tolerant species. Conditioning with feast and famine cycles improved recovery time and tolerance to feed and shear shocks (Hoffmann et al., 2008). 

Furthermore, microorganism production and conversion processes often introduce unwanted by-products or create products that negatively affect bioreactor operation. For example, protein-producing microorganisms, which are often used in pharmacokinetics, produce a mixture over time that is damaging to the bacteria aside from the surface-active agent properties of the protein. Shear is tolerated by the microorganisms in this mixture, but air-fiquid interfaces, which are naturally 

Baffle designs for gas-liquid stirred-tank bioreactors can be used with solids that have a similar density as the liquid. If the solid phase is denser than the liquid, baffles should be much thinner if they are used at all. This is due to the fact that the decreased level of turbulence may lead to stratification, dead zones, and/or recirculation loops near the baffles. These occurrences can cause excessive buildup of solid material and poor performance. Therefore, baffles used for this purpose may have a plate thickness as small as r/24 (Oldshue, 1983). 

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In these procedures, the choice of derivatives and enzyme is important. Sometimes it is possible to get a D-amino acid which remains in the microbial culture supplemented with DL-amino acids (54). 

Ethanol fermentation is a particularly good example of product accumulation inhibiting the microbial culture. Most strains of yeast have a much slower alcohol production rate when ethanol reaches about ten percent, and the wine or said strains that achieve over 20 percent by volume of ethanol are very, very slow. A system known as the Vacuferm for removal of alcohol by distillation as it is formed is... 

Recombinant DNA technology now verges on the ability to engineer at will the genetic constitution of organisms for desired ends. The commercial production of therapeutic biomolecules in microbial cultures is already established (for example, the production of human insulin in quantity in E. coli cells). Agricultural crops with desired attributes, such as enhanced resistance to her-... 

In Figure 6.3, we have provided a summary of the possible strategies for improving yields of antibiotics produced by microbial cultures and for diversifying the nature of the products that are manufactured. 

In this chapter, by using the examples of -lactams we have briefly examined how microbial cultures may be used to produce sufficient antibiotics to meet market demands. We have also explained how enzymes (or cells) may be used to biotransform, and thereby diversify, antibiotics. By outlining the history of penicillin production, we explained how analysis and manipulation of culture regimes may be used to enhance the yields of antibiotics (and other secondary products). These studies led to die concept of directed biosynthesis by precursor feeding. 

Microbial cultures may foam when they are subjected to vigorous mechanical stirring and aeration. If this foaming is not controlled, culture is lost by entrainment in the exhaust gases and so there are systems, often automatic, for detecting incipient foaming. 

Around the world there are hundreds of official methods from various government and professional sources that specify ATCC microorganisms as biological RMs. The following six examples serve as examples of many organizations arotmd the world that specify ATCC microbial cultures as biological RMs ... 

ATCC issues Certificates of Analysis with cultures. Although ATCC Certificate of Analysis do not meet the specific requirements of ISO Guide 31, they do show that the biological RM culture has been authenticated and/or specific characteristics have been verified. Each ATCC Certificate of Analysis is lot-specific and includes expiration dates, the specific seeds used for propagation, and selected biochemical and morphological characteristics that are indicative of the culture. ATCC also aims to provide a Product Sheet for each microbial culture, with instructions for propagation, special features of the organism, and any imusual observations or properties. 

Microbiologic studies that allow for direct examination of a specimen (e.g., sputum, blood, or urine) also may aid in a presumptive diagnosis and give an indication of the characteristics of the infecting organism. Generally, microbial cultures are obtained with a Gram stain of the cultured material. 

An 02 flow must be maintained through the contaminated zone at a level sufficient for the aerobic biodegradation of contaminants. Note that during bioventing the main aim is the maximum utilization of 02 by the microbial cultures. For this reason, air flow rate is usually an order of magnitude lower than that applied in simple SVE systems. A simple empirical rule is that the mean residence time of air in the contaminated soil pore volume should be between 1 and 2 days. 

Microbial oxidation of drug substrates occurs in a similar fashion to mammalian oxidative biotransformation. In contrast, microbial cultures rarely catalyze conjugations comparable to those in mammalian system (glucuronidation, sulfation and GSH conjugation). It is thus not surprising that microbial bioreactors are mainly used in the synthesis of oxidative metabolites. 

Substrate can be added to the cultures as a solid, a suspension, or a solution in DMSO, methanol, ethanol, acetonitrile or water. As the microbial culture generally has high tolerance toward organic solvents, there is less restriction on the choice and amount of solvent to be used for dispensing the substrate. Aqueous solubility of substrates normally will not affect compound loading, as a compound with poor aqueous solubility will likely be absorbed by the cells and still be subjected to biotransformation. 

Unique Extremophilic Microorganisms, Collection of Unique Microbial Cultures, Russian Academy of Sciences (UNIQEM). 

Clark et al. [81] determined the time course of A-acetylation of primaquine by Streptomyces roseochromogenous and Streptomyces rimosus by quantitative high performance liquid chromatographic analyses of the culture broths. The A-5-bistri-fluoroacetyl derivative of primaquine was used as an internal standard in the analysis for the quantitation of primaquine A-acetate in microbial culture broths. S. roseochromogenous forms the highest level of primaquine A-acetate at 24—36 h after substrate addition, while S. rimosus is slower in its acetylation, peaking at 3 days after substrate addition. The formation of a novel dimeric compound from the reaction of primaquine with 8-(4-phthalimido-l-methylbutylamino)-6-methoxy quinoline is also reported. 

Rapid intestinal transit may result in a false-positive breath test, in particular when hyperosmolar nonabsorbable substrates are used. A false-negative outcome in patients with culture-proven Gram-negative bacilli in the upper gut further query the sensitivity and usefulness of breath tests for clinical practice [10-13]. Positive microbial culture from small intestine is thus advantageous when major alterations of clinical management are considered. 

Table 4 Biodegradation of azo dyes and their intermediates by mixed microbial cultures...

Direct Black 38 Mixed microbial culture isolated from an aerobic bioreactor treating textile wastewater The dye was transformed into benzidine and 4-aminobiphenyl followed by complete biodegradation of these toxic intermediates [134]... 

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