Microbial growth and product formation

Strategies for Optimizing Microbial Growth and Product Formation... 

The thermodynamic theory outlined above can, in principle, be straightforwardly applied to the description of microbial growth and product formation. In order to perform such an analysis, thermodynamic data are needed regarding the compounds which are exchanged with the environment, i.e. the partial molar enthalpies... 

The main substrates used in industrial microbiology today are glucose, sucrose, starch, glycerol, or acetate. Additionally, waste substrates as sugarcane and sugar beet molasses, corn steep liquor, deproteinized whey, or waste streams from food and paper industries are used very often as medium components. In some cases, complex vitamin and amino acid rich medium components like yeast extract, malt extract, or peptones have to be added to the media for optimal microbial growth and product formation. For the production of more complex compounds like antibiotics, chemical precursors have to be added sometimes. 

Aeration and agitation plays a significant role in the SSF process because it faces two fundamental problems O2 demand in the aerobic process, and heat and mass transport phenomena in a heterogeneous system [24, 26]. O2 demand in SSF can be satisfied with relatively low aeration levels. Agitation may also break the mycelia-substrate bed depending on the nature of the solids, which can disrupt the growth and metabolism. However, there is always a compromise between the rate of aeration, microbial growth, and product formation. Several authors continue to study aspects related to aeration in different kinds of reactor setup in SSF [27, 28]. 

From kinetics studies of unicellular organisms, a set of mathematical expressions have been established to represent the most frequent phenomena in bioprocesses. These phenomena involve a limitation or inhibition of growth and product formation, caused by the presence of substrates, products, or byproducts in culture media. Many of these expressions do not derive from known kinetic mechanisms. In fact, they are simply mathematical expressions with fitted parameters that are able to reproduce experimentally observed kinetic profiles. These equations have been derived and used in many unstructured microbial or cell models. 

B) If there are two microbial species present show the dynamics of microbe growth and product formation from each and in toto. Find A1,B1,C1 and A2,B2,C2 for each microbe. 

The present review deals with the characterization of model protein foams and foams of various cultivation media. The suppression of foaming by antifoam agents and their effect on the oxygen transfer rate, microbial cell growth and product formation are discussed. The influence of process variables on the recovery of proteins by flotation without and with surfactants and mathematical models for protein flotation are presented. The effect of cultivation conditions, flotation equipment and operational parameters on foam flotation of microorganisms is reviewed. Floatable and non-floatable microorganisms are characterized by their surface envelope properties. A mathematical model for cell recovery by flotation is presented. Possible application areas of cell recovery by flotation are discussed. 

In the steady-state case, the reasoning presented formally validates the treatment of microbial metabolism in terms of a gross stoichiometric equation of growth and product formation (Roels, 1980a). This formalism, however, results in complicated equations that offer little advantage over other equations. Therefore, only situations of limited complexity can be studied in detail. 

Microbial activities like growth and product formations can be regarded as a sequence of enzymatic reactions. On this basis Ferret (1960) constructed a kinetic model for a growing bacterial cell population. The main pathways for major nutrients are considered together with pathways for minor nutrients and trace elements linked to each other. This metabolic network can be simplified with the aid of the concept of the rate-determining step (rds), resulting in a master reaction or bottleneck that limits the total flux and the rate of the process. 

Heiskanen, H., Virkajarvi, 1., Viikari, L., 2007. Tbe effect of syngas composition on the growth and product formation of Butyribacterium methylotrophicum. Enzyme and Microbial Technology 41 (3), 362—367. 

In any quantitative assessment of growth and/or product formation, it is essential to link formation of microbial biomass and products with the utilisation of substrate and nutrients. In the case of microbial biomass production, the total amount of cell mass yield formed is often proportional to the mass of substrate utilised. Mathematically this is coefficient expressed as the corresponding ratio, or yield coefficient ... 

The B. licheniformis JF-2 strain produces a very effective surfactant under conditions typical of oil reservoirs. The partially purified biosurfactant from JF-2 was shown to be the most active microbial surfactant found, and it gave an interfacial tension against decane of 0.016 mN/m. An optimal production of the surfactant was obtained in cultures grown in the presence of 5% NaCl at a temperature of 45° C and pH of 7. TTie major endproducts of fermentation were lactic acid and acetic acid, with smaller amounts of formic acid and acetoin. The growth and biosurfactant formation were also observed in anaerobic cultures supplemented with a suitable electron acceptor, such as NaNO3[1106]. 

Heat flux calorimeters are bioreactors equipped with special temperature control tools. They provide a sensitivity which is approximately two orders of magnitude better than that of microcalorimeters, e.g. [33,258]. The evaluation and description of microbial heat release is based on a heat balance heat yields and the heat of combustion of biological components are central parameters for quantification [70]. Measurements obtained so far have been used to investigate growth, biomass yield, maintenance energy, the role of the reduction degree of substrates, oxygen uptake [414] and product formation [272]. 

Microbial cells contain or produce at least 2500 different enzymes which can catalyze biochemical reactions leading to growth, respiration and product formation. Most of these enzymes can readily be separated from cells and can display their catalytic activities independently of the cells. Although microbial enzyme activities have been observed for many centuries, only recently have microbial enzymes been commercially utilized. 

Physical instability of liquid formulations involves the formation of precipitates, less-soluble polymorphs, adsorption of the drug substances onto container surfaces, microbial growth, and changes in product appearance. Evaluation of product acceptability is subjective and includes properties such as color, odor, taste, and clarity. Dye stability depends on the... 

Figure 5.44. Schematic representation of the numerical Kono approach to microbial product formation expressed as the general formulas of the rates of growth and production rp, including different growth phases (1, induction 2, transient 3, exponential and 4, declining), according to Equ. 5.126 and Table 5.2. (Adapted from Kono and Asai, 1968a-c, 1969a-c) (a) both and kp2 have a positive value. The dotted lines take into account a linear growth phase, as shown in Fig. 5.19. (b) kp >0, kp2 = 0. (c) kpi = 0, kp2 > 0. (d) /cpi > 0, kp2 < 0.

Seafood. Citric acid is used in combination with other preservatives/antioxidants to lower the pH to retard microbial growth, which can lead to spoilage, formation of off-flavors, and colors on fish and other seafood products. 

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