Biochemical Miscellaneous
- In a well aerated and agitated microbial culture, the ‘supply' of oxygen is equal to ‘demand' (uptake) of the growing culture. The KLa for such a system will be (KLa = volumetric mass transfer coefficient, C* = dissolved oxygen concentration in liquid in equilibrium with gaseous oxygen,C = instantaneous value of dissolved oxygen concentration, ‘r' = specific oxygen uptake rate per unit weight of cells, X = dry weight of the cells per unit volume)
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The “gas out-gas in” method can directly determine the volumetric mass transfer coefficient in a bioreactor system and provide estimates of the volumetric microbial oxygen uptake rate and the average oxygen saturation concentration at the gas-liquid interface. The rate of oxygen transfer from the bubble air to the liquid phase is described by the equation :
dCL / dt = KLa (C* – CL)
⇒ KLa = dCL/dt * 1/ (C* – CL)
⇒ KLa = r*X/(C* – CL)
Where r*X = dCL/dt, r is the specific oxygen uptake rate per unit weight of cells and X is the dry weight of cells per unit volume.
For reliable measurements, deconvolution of the oxygen probe measurements must be made. Correct Option: A
The “gas out-gas in” method can directly determine the volumetric mass transfer coefficient in a bioreactor system and provide estimates of the volumetric microbial oxygen uptake rate and the average oxygen saturation concentration at the gas-liquid interface. The rate of oxygen transfer from the bubble air to the liquid phase is described by the equation :
dCL / dt = KLa (C* – CL)
⇒ KLa = dCL/dt * 1/ (C* – CL)
⇒ KLa = r*X/(C* – CL)
Where r*X = dCL/dt, r is the specific oxygen uptake rate per unit weight of cells and X is the dry weight of cells per unit volume.
For reliable measurements, deconvolution of the oxygen probe measurements must be made.
- Structured William's model
P. can describe the changes in intracellular components of the cell during growth
Q. cannot describe the death phase of the cells
R. can describe the variation of size of cells in the different phases of growth
S. cannot describe the lag period of growth
Which one of the following is correct?
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Williams proposed a simple structured model that divides the biomass into two parts: Part 1 is composed of intermediates, enzymes, and other entities involved in the formation of materials used for synthesis of structural and genetic material; Part 2 is the structural and genetic part of the biomass. It can be used to describe the change in intracellular components during cell growth. In the different phases of cell growth, this model enables analytical depiction and explanation of the variation in the size of the cells. But the model is not structured for reasoning with the death phase of the cells.
Correct Option: B
Williams proposed a simple structured model that divides the biomass into two parts: Part 1 is composed of intermediates, enzymes, and other entities involved in the formation of materials used for synthesis of structural and genetic material; Part 2 is the structural and genetic part of the biomass. It can be used to describe the change in intracellular components during cell growth. In the different phases of cell growth, this model enables analytical depiction and explanation of the variation in the size of the cells. But the model is not structured for reasoning with the death phase of the cells.
- Determine the correctness or otherwise of the following Assertion (A) and the Reason (R).
Assertion : In synchronous culture, majority of the cells move to next phase of the cell cycle simultaneously.
Reason : Synchronous culture could be obtained by starving cells for essential nutrient components.
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Synchronous growth of a bacterial population is that during which all bacterial cells of the population are physiologically identical and in the same stage of cell division cycle at a given time. Synchronous growth helps studying particular stages or the cell division cycle and their interrelations. A synchronous culture can be obtained either by manipulating environmental conditions such as by repeatedly changing the temperature or by adding fresh nutrients to cultures as soon as they enter the stationary phase, or by physical separation of cells by centrifugation or filtration. Synchronous cultures rapidly lose synchrony because not all cells in the population divide at exactly the same size, age or time.
Correct Option: B
Synchronous growth of a bacterial population is that during which all bacterial cells of the population are physiologically identical and in the same stage of cell division cycle at a given time. Synchronous growth helps studying particular stages or the cell division cycle and their interrelations. A synchronous culture can be obtained either by manipulating environmental conditions such as by repeatedly changing the temperature or by adding fresh nutrients to cultures as soon as they enter the stationary phase, or by physical separation of cells by centrifugation or filtration. Synchronous cultures rapidly lose synchrony because not all cells in the population divide at exactly the same size, age or time.
- Maximum specific growth rate (µmax) of a microorganism is calculated by taking the (ln = loge, X = biomass, t = time)
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By Monod model, ln X Vs t graph is linear and slope = μ, where μ is specific growth rate, μmax is maximum specific growth rate. It represents the log phase of the growth.
Correct Option: B
By Monod model, ln X Vs t graph is linear and slope = μ, where μ is specific growth rate, μmax is maximum specific growth rate. It represents the log phase of the growth.
Direction: A microorganism grows in a continuous ‘chemostat' culture of 60 m3 working volume with sucrose as the growth limiting nutrient at dilution rate, D = 0.55 h–1. The steady state biomass concentration is 4.5 Kg dry biomass m–3 and the residual sucrose concentration is 2.0 Kg m–3. The sucrose concentration in the incoming feed medium is 10.0 Kg m–3.
- What would be the yield YX/S (Kg biomass/Kg substrate)?
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We know, Yield of biomass, YX/S = Biomass produced/ Substrate consumed
Now, Substrate consumed, S = Initial substrate concentration (Si) – Final substrate concentration (Sf )
= Si – Sf
Si = 10 kg/ m3 and Sf = 2 kg/ m3
Biomass produced, X = 4.5 kg dry biomass/ m3
Therefore, YX/S = X/ (Si – Sf) = 4.5 (10 – 2)
= 0.562 Kg of biomass/ kg of the substrate. Correct Option: A
We know, Yield of biomass, YX/S = Biomass produced/ Substrate consumed
Now, Substrate consumed, S = Initial substrate concentration (Si) – Final substrate concentration (Sf )
= Si – Sf
Si = 10 kg/ m3 and Sf = 2 kg/ m3
Biomass produced, X = 4.5 kg dry biomass/ m3
Therefore, YX/S = X/ (Si – Sf) = 4.5 (10 – 2)
= 0.562 Kg of biomass/ kg of the substrate.
