Dr. Saleha Shamsudin PPK BIOPROSES, UniMAP 013-2081261 Kinetic of Growth in Continuous Culture Some specific devices for continuous culture, derivation for ideal chemostat, application of chemostat and its deviation of ideality. Morton Coutts (1904-2004), father of continuous fermentation Morton Coutts' plan for continuous fermentation at Dominion Breweries' Waitemata Brewery was patented as a world first in 1956. BATCH Culture environment changes continually Growth, product formation and substrate utilization terminate after a certain time interval CONTINUOUS CULTURE Fresh medium is continually supplied to a wellstirred culture Products and cells are simultaneously withdrawn Growth and product formation can be maintained in constant environment condition for prolonged periods in continuous culture and supplies uniformquality products. Some Specific Devices for Continuous Culture Chemostat and Turbidostat Chemostat – constant chemical environment, When chemostat is at steady state, the nutrient, product and cell concentrations are constant Turbidostat – the cell concentration in the culture vessel is maintained constant by monitoring the optical density of the culture and controlling the feed flow rate. When the turbidity of the medium exceeds the set point, a pump is activated and fresh medium is added The Ideal Chemostat The Ideal Chemostat Fresh sterile medium Cell is removed at the same rate Control elements: pH, DO control units Volume (constant) system is steady state Feed media are sterile, endogeneous metabolism or death rate is negligible Cells are removed equal to their growth rate which is equal to dilution rate. In the chemostat, growth rate is limited by atleast one substrate, substitute the Monod equation for µg. A plot of 1/ug versus 1/S can be used to estimate value for um and Ks. If D<um, we can relate effluent substrate concentration to dilution rate by: Material balances on cell and growth-limiting substrate concentrations around the reactor yield the following: S0 and S = feed and effluent substrate (g/l) qp = specific rate of extracellular product formation Yx/s and Yp/s = yield coefficents When extracellular product formation is negligible, qp and the system is at steady state (dS/dt=0) Eq. 6.70 Since µg=D at steady-state if kd=0 Using eq. The steady-state cell concentration can be expressed as; Consider the effect the inclusion of endogeneous metabolism; eq. 6.66 becomes: Substitute Eq. 6.73b into steady-state balance, assuming no product formation (Eq. 6.70), we find Equation 6.73 can be rearranged to: Yx/s ms = maintanance coefficient; Yx/sAP apparent yield; Plot 1/ Yx/sAP against 1/D to find ms is the slope and 1/ Yx/sAP is the intercept In the present of endogenous metabolism; Consider the conversion of extracellular substrate into extracellular product. The balance on product formation is: qp is described by equation 6.16, 6.17 and 6.18 depending on the types ofmicrobial products For substrate balance, Eq. 6.69 becomes: and yield: Application of Chemostat •To grow microorganisms on very toxic nutrients • To select mutants with a higher affinity to the growth-limiting nutrient • To select the species that are optimally adapted to the growth limitation and culture conditions in a mixed population • To study the properties of organisms at selected growth rates • To gather steady state data about an organism in order to generate a mathematical model relating to its metabolic processes Continuous industrial microbial processes are much less common than batch processes, but most biological waste treatment steps are operated continuously I. Continuous cultivation of rumen microorganisms, a system with possible application to the anaerobic degradation of lignocellulosic waste materials (Huub et al., 1986) II. A bioprocessing mode for simultaneous fungal biomass protein production and wastewater treatment using an external air-lift bioreactor (Bo et al.,2001) Continuous fermentation has been successfully applied in: • Brewing industry (Dennis et al., 2000) • Single cell protein production (King, 1982).
© Copyright 2024