Fermentation aeration rate

Various species and many strains oiyAcetobacter are used in vinegar production (48,49). Aeration rates, optimum temperatures and nutrient requirements vary with individual strains. In general, fermentation alcohol substrates require minimal nutrient supplementation whde their addition is necessary for distilled alcohol substrates. 

Fermentation biomass productivities usually range from 2 to 5 g/(l h). This represents an oxygen demand in the range of 1.5 to 4 g 0/(l h). In a 500-m fermenter, this means achievement of a volumetric oxygen transfer coefficient in the range of 250 to 400 h"f Such oxygen-transfer capabihties can be achieved with aeration rates of the order of 0.5 (volume of air at STPA ohime of broth) and... 

Bioprocess Control An industrial fermenter is a fairly sophisticated device with control of temperature, aeration rate, and perhaps pH, concentration of dissolved oxygen, or some nutrient concentration. There has been a strong trend to automated data collection and analysis. Analog control is stiU very common, but when a computer is available for on-line data collec tion, it makes sense to use it for control as well. More elaborate measurements are performed with research bioreactors, but each new electrode or assay adds more work, additional costs, and potential headaches. Most of the functional relationships in biotechnology are nonlinear, but this may not hinder control when bioprocess operate over a narrow range of conditions. Furthermore, process control is far advanced beyond the days when the main tools for designing control systems were intended for linear systems. 

The inoculate was prepared in 250 ml flasks containing 100 ml of growth medium, which is inoculated with 10 ml of spore suspension. The mixture was shaken at 250 rpm and the temperature was controlled at 26 °C for 48 h. Then, 110 ml of resulting mycelia suspension is used to inoculate a 1000 ml broth in the airlift fermenter. The sterilised media are slowly pumped into the bioreactor at a flow rate of about lOOmlh-1 until 2 1 working volume is fully utilised. Aeration rates of 0.5, 1 and 2vvm (1,2 and 4 1 air/min) are used.6,7 Samples were taken at 24 hour intervals and evaluated for biomass, sugars and antibiotic concentrations. 

Calculate mass transfer coefficient in a 60 m3 fermenter with a gas and liquid interfacial area of a = 0.3 m2-m 3, given pbroth = 1200kg m-3. The small reactor has working volume of 0.18m3, 1 vvm aeration rate. Oxygen transfer rate (OTR) is 0.25kmol in 3 h 3. There are two sets of impellers, and flat-blade turbine types of impeller were used, HL= 1.2/),. Find the exact specifications of a large fermenter. 

A continuous fermenter is operated at a series of dilution rates though at constant, sterile, feed concentration, pH, aeration rate and temperature. The following data were obtained when the limiting substrate concentration was 1200 mg/1 and the working volume of the fermenter was 9.8 1. Estimate the kinetic constants Km, //, and kd as used in the modified Monod equation ... 

Batch growth was started by inoculating the fermenter with 100 mL of a freshly grown preculture of E. coli JMlOl (pSPZlO) (see Procedure 2, Section 12.8.2). The pH was kept at 7.1, the aeration rate was set to 2 L min and the stirrer speed and temperature were 1300 rpm and 30 °C respectively. 

The interfacial area per unit volume a is, again, a difficult quantity to measure in a fermenter since it depends on the number and size of the air bubbles entrained in the fermentation broth. These, in turn, are dependent on such factors as the aeration rate, the rheology of the broth at that instant and the presence or otherwise of surfactants. As a result, the quantity KLa tends to be treated as a single entity in experimental measurements of oxygen transfer rates in fermenters. 

For aerobic fermentations, air needs to be supplied continuously. Typical aeration rates for aerobic fermentation are 0.5 - 1.0 vvm (air volume per liquid volume per minute). This requires an enormous amount of air. Therefore, not only the medium but also the air must be free of microbial contaminants. All of the sterilization techniques discussed for medium can also be employed for air. However, sterilization of air by means of heat is economically impractical and is also ineffective due to the low heat-transfer efficiency of air compared with those of liquids. The most effective technique for air sterilization is filtration using fibrous or membrane filters. 

Since in animal cell culture processes the effects of mechanical stress are much more relevant than in microbial fermentations (Chisti, 1993), it is quite common to adopt scale-up criteria that are associated with cell damage (Joshi et al., 1996), such as constant peripheral impeller velocity, constant aeration rate, and constant integrated shear stress (Croughan et al., 1987). 

Several special terms are used to describe traditional reaction engineering concepts. Examples include yield coefficients for the generally fermentation environment-dependent stoichiometric coefficients, metabolic network for reaction network, substrate for feed, metabolite for secreted bioreaction products, biomass for cells, broth for the fermenter medium, aeration rate for the rate of air addition, vvm for volumetric airflow rate per broth volume, OUR for 02 uptake rate per broth volume, and CER for C02 evolution rate per broth volume. For continuous fermentation, dilution rate stands for feed or effluent rate (equal at steady state), washout for a condition where the feed rate exceeds the cell growth rate, resulting in washout of cells from the reactor. Section 7 discusses a simple model of a CSTR reactor (called a chemostat) using empirical kinetics. 

The protease fermentation of the Bacillus bacteria takes place under strictly aseptic conditions in conventional equipment for submerged fermentations. The aeration rate is about 1 vvm (volume of air per volume of medium per minute). Vigorous agitation is used to improve air distribution and oxygen transfer. The fermentation temperature is around 37°C, and the time cycle is 2-4 days. 

Blue cheese flavors have been prepared via submerged culture fermentations in a sterile milk-based medium using Penicillium rogueforti(63). The fermentations are conducted under pressure with low aeration rates with optimal flavor production occurring from 24-72 hours. Similarly, Kosikowski and Jolly(64) prepared blue cheese flavors from the fermentation of mixtures of whey, food fat, salt and water by P roqueforti. Dwivedi and Kinsella(65) developed a continuous submerged fermentation of P. roqueforti for production of blue cheese flavor. 

Aeration is a significant cost factor in the industrial production of citric acid. The industrial practice uses relatively low aeration rates, initially at 0.01 wm and rises to 0.5 to 1 wm as fermentation proceeds. For the bubble column. 

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