Using Batch And Continuous Cultures Biology Essay

Using Batch And Continuous Cultures Biology EssayMicrobial growth causes an increase in a microorganisms size and race account and can be studied utilize push-down store and constant culture mediums (Lansing M. Prescott et al. 1990, 1993, p. 112)Batch culturesNutrient consumption and build up of venomous by-products slow down and land up the growth of bacteria. One method to avoid this is to use batch culture system. This involves culturing bacteria in smooth-spoken medium within a closed system where no fresh medium is added during the incubation achievement and thus the food concentration declines and waste products accumulate during the growth of bacteria (Slonczewski comfort 2009, p. 137).The microorganisms reproduce by binary fission and their growth can be expressed as the logarithm of cubicle add together and can be plotted against incubation time. This result in a curve that has 4 unadorned stagecoachs as shown in Figure 1 (Lansing M. Prescott et al. 1990, 19 93, p. 113)Figure 1 Curve showing manikins of growth for batch cultures (taken from Tortora et al. 1992)Lag Phase- when microorganisms atomic number 18 introduced into fresh culture medium no increase in cell frame or mass occurs. This marks the beginning of the Lag Phase which is necessary as the cells may be old and depleted of ATP, certain essential cofactors and ribosome, the medium may be antithetic from the one that the microorganism was growing in previously, or the microorganism may have suffered injuries and may need time to withhold (Lansing M. Prescott et al. 1990, 1993, p. 113).Length of the Lag Phase varies depending on factors such as age of culture, temperature changes and differences between old and saucily media. When cells are transferred from a complex medium to a fresh complex medium recur phase is very short, whereas when cells are transferred from complex medium into a minimally defined medium, lag phase is prolonged (Slonczewski Foster 2009, p. 137).E xponential Phase- during this phase the set out of growth of microorganisms is constant and they divide and become double in result at regular intervals and at the maximal rate possible given their genetic potential, constitution of the medium and the conditions of growth (Lansing M. Prescott et al. 1990, 1993, p. 113).As batch cultures are not synchronous every cell has an equal times time and each cell divides at a different moment, as hence the cell number rises smoothly. When the medium is abruptly changed nutritional downshifts or nutritional upshifts cause cells experiencing balanced exponential growth to be thrown into metabolic chaos that is unbalanced growth (Slonczewski Foster 2009, p. 138). Exponential phase cultures are apply in bio chemic and physiological studies as the population is most uniform in terms of chemical and physiological characteristics during this phase (Lansing M. Prescott et al. 1990, 1993, p. 113).Stationary Phase- during this phase the growth c urve becomes horizontal as growth of the population ceases. Bacteria innovate this phase at a population level of around cells per ml. The total number of viable organisms remains constant callable to a balance between cell division and cell death or because the population ceases to divide but still remains metabolically active. Microbial populations enter the stationary phase due(p) to reasons such as nutrient limitations, oxygen avail dexterity and accumulation of toxic waste products (Lansing M. Prescott et al. 1990, 1993, p. 114).Death Phase- characteristic feature of this phase is decline in the number of viable cells due to nutrient deprivation and buildup of toxic wastes. The death of a microbial population is logarithmic. The extended survival of particularly resistant cells may reduce the death rate (Lansing M. Prescott et al. 1990, 1993, p. 114). In this phase the number of cells that die during a given time period is proportional to the number of cells that existed at the beginning of the time period (Slonczewski Foster 2009, p. 138).Advantages of using batch culturesThey allow versatility and can be used for many different reactions (Nielsen Villadsen 1994, p. 344).They are riskless and do not pose a threat of strain mutation (Nielsen Villadsen 1994, p. 344).They ensure complete metempsychosis of substrate (Nielsen Villadsen 1994, p. 344).The changing conditions during the use of batch cultures affect the physiology and growth of bacteria and hence highlight the ability of bacteria to adapt to its environment (Slonczewski Foster 2009, p. 137).Disadvantages of using batch culturesUse of batch cultures requires highly arch(prenominal) fight thus increasing labor costs (Nielsen Villadsen 1994, p. 344).Use of batch cultures is time consuming (Nielsen Villadsen 1994, p. 344). harmonise to Xuezhen Kang (2000) changing concentrations of products and reactants, varying pH and oxidation-reduction potential makes interpretation of results diff icult.According to Xuezhen Kang (2000) complicated mix of growing, anxious(p) and dead cells also makes interpretation difficult.Continuous culturesIn a around-the-clock culture system the microorganisms are grown in an open system where constant environmental conditions are maintained through nonstop provisions for new nutrients and removal of waste. This allows the microbial population to remain in exponential growth phase and at a constant biomass concentration for an extended period of time (Lansing M. Prescott et al. 1990, 1993, p. 120).2 main types of continuous culture systemsChemostat- this system ensures that sterile medium containing essential nutrients in limiting quantities is fed into the culture vas at the same rate as the medium containing the microorganism is removed (Lansing M. Prescott et al. 1990, 1993, p. 120).The growth rate of microorganisms is persistent by the rate at which new medium is fed into the growth chamber. The final cell parsimoniousness depen ds on the concentration of the limiting nutrient (Lansing M. Prescott et al. 1990, 1993, p. 120).Dilution rate D is used to express the rate of nutrient exchange and is defined as the rate at which medium flows through the culture vessel telling to the vessel volume. f re personates flow rate and V represents volume of the vessel (Lansing M. Prescott et al. 1990, 1993, p. 120).D=f/Vf (ml/hr) and V(ml)(Lansing M. Prescott et al.1990, 1993, p. 120)Microbial population levels and times time depend on the dilution rate. As the dilution rate increases generation time shortens and growth rate rises. Under these conditions the limiting nutrient will be almost all told depleted and it begins to rise at higher dilution rates as there are fewer microorganisms present to use it. At low dilution rate a rise in both cell constriction and growth rate occur (Lansing M. Prescott et al. 1990, 1993, p. 120).Turbidostat- involves a photocell that measures the turbidity of the culture in the growt h vessel. The rate of flow of the media through the growth vessel is automatically regulated to maintain a predetermined turbidity. here(predicate) the dilution rate remains constant and there is no limiting nutrient in the culture. The turbidostat operates best at high rates of dilution (Lansing M. Prescott et al. 1990, 1993, p. 120).Advantages of using continuous culturesThey allow good utilization of the bioreactor and ensure low labor costs (Nielsen Villadsen 1994, p. 344).They are efficient and ensure high and constant productivity due the autocatalytic nature of microbial reaction taking place (Nielsen Villadsen 1994, p. 344).They allow detailed analysis of microbial physiology at different growth rates as all cells of the population achieve a steady state and hence has significant industrial and research applications (Slonczewski Foster 2009, p. 139).The situation in a chemostat resembles the growth of bacteria in nature where the growth rates are very low (Slonczewski Foster 2009, p. 140).According to Xuezhen Kang (2000) their use eliminates the lag the organism experiences before going into high productivity.Disadvantages of using Continuous CulturesSometimes they fail to produce results due to infection and mutations of microorganisms that result in production of non producing strains (Nielsen Villadsen 1994, p. 344).Use of these cultures requires downstream equipments to be designed for low volumetrical rates and continuous operation (Nielsen Villadsen 1994, p. 344).In conclusion, we see that both culture mediums have their advantages and disadvantages and while using either one, these should be kept in mind.