Questions without answers in Bioreaction Engineering

The correct sequence of the four steps involved in anaerobic production of biogas from complex organics is:Hydrolysis → Acidogenesis → Acetogenesis → MethanogenesisMethan...

A microbial culture is being grown in a bioreactor with continuous aeration. The dissolved oxygen probe provided with the system shows a reading of zero. In this context,...

In an aerobic fermentation with air sparging, which of the following options can be used to increase the volumetric mass transfer coefficient for oxygen transfer?Using pu...

For an ideal plug flow reactor, which of the following statements is/are true?It can be approximated by a large number of ideal continuous stirred tank reactors connected...

A $\text{CSTR}$ with a volume of $100 \mathrm{~m}^{3}$ is operated in cell recycle mode. At a volumetric flow rate of $10 \mathrm{~m}^{3}$ day ${ }^{-1}$ and effluent bio...

A batch sterilizer is being operated at $121^{\circ} \mathrm{C}$ for sterilizing a medium containing microbial cells. Assume that the thermal deactivation of cells is a f...

A substrate is consumed in a zero order reaction such that its concentration falls from $42 \mathrm{~g} \mathrm{~L}^{-1}$ to $14 \mathrm{~g} \mathrm{~L}^{-1}$ in $4$ hour...

A microbe that follows Monod growth kinetics on a limiting substrate (maximum specific growth rate of $0.5 \mathrm{~h}^{-1}$ and Monod constant of $0.1 ~\mathrm{mg} \math...

It is desired to cultivate $150$ mg (dry weight) microbial cells with an empirical formula of $\mathrm{C}_{5} \mathrm{H}_{7} \mathrm{O}_{2} \mathrm{~N}$. If the phosphoru...

A packed bed bioreactor with length $1 \text{~m}$ and inside diameter $10 \text{~cm}$ has liquid flowing at an interstitial velocity of $1 \mathrm{~cm} \mathrm{~s}^{-1}$....

In a fermentation process, each mole of glucose is converted to biomass $\left(\mathrm{CH}_{1.8} \mathrm{O}_{0.5} \mathrm{~N}_{0.2}\right)$, with a biomass yield coeffici...

Aqueous two-phase extraction is used to recover α-amylase from a solution. A polypropylene glycol-dextran mixture is added and the solution separates into upper and lower...

Under complete cell washout condition in a chemostat with sterile feed, which of the following statements is/are correct?Biomass concentration in the reactor is maximumS...

Aspergillus niger is grown in a $10,000$ L stirred batch bioreactor under aerated conditions to produce citric acid. At steady state oxygen transfer conditions, the speci...

Ethanol is produced in a $10,000$ L stirred bioreactor using an impeller of diameter $1 \mathrm{~m}$. The density and viscosity of fermentation broth are $1000 \mathrm{~k...

A fermentor is filled with medium at a rate of $1 \mathrm{~L} \mathrm{~min}^{-1}$. A leak develops at the bottom of the fermentor when the medium in the fermentor reaches...

Consider scale-up of fungal fermentation from a $20 \mathrm{~L}$ model-type to $20,000 \mathrm{~L}$ prototype stirred tank reactor. The model-type and prototype have the ...

A batch cultivation of E. coli follows zeroth order Monod’s growth kinetics. The cell growth is terminated when the residual dissolved oxygen concentration attains 10% of...

The following schematic diagram shows a chemostat with cell recyclewhere $\mathrm{F}_0$ and $\mathrm{F}_{\mathrm{r}}$ are the volumetric flow rates (in $L \cdot h^{-1}$ )...

The values of the consistency index ' $K$ ' and the flow behavior index ' $n$ ' of a dilatant fluid are 0.415 (in CGS units) and $1.23$, respectively. The value of the ap...

A fermentation broth of density $1000 \; \text{kg m}^{-3}$ and viscosity $10^{-3} \; \text{kg m}^{-1} \text{s}^{-1}$ is mixed in a $100\;\text{L}$ fermenter using a $0.1 ...

Which of the following statements are $\text{CORRECT}$ for an enzyme entrapped in a spherical particle?Effectiveness factor is ratio of the reaction rate with diffusion-l...

Figure below depicts simplified metabolic and transport reactions taking place in the production of $\text{B}$ from $\text{A}$ in a cell. The subscript $ i\text{’}$ refer...

The amount of biomass in a reactor at the end of the batch process is $50 \; \text{g}.$ Fed-batch operation is initiated by feeding the substrate solution at a constant r...

An enzyme catalyzes the conversion of substrate $\text{A}$ into product $\text{B}.$ The rate equation for this reaction is$-r_{A}= \dfrac{\text{C}_{A}}{5+C_{A}} \text{mol...

Liquid-phase mass transfer coefficient $(k_{L})$ is measured in a stirred tank vessel using steady-state method by sparging air. Oxygen uptake by the microorganism is mea...

Consider the growth of $\textit{S. cerevisiae}$ under aerobic condition in a bioreactor and the specific growth rate of yeast is $0.5\; \text{h}^{-1}.$ The overall reacti...

A pilot sterilization was carried out in a vessel containing $1000\; \text{m}^{3}$ medium with an initial spore concentration of $10^{8} \;\text{spores/ml.}$ The accepted...

The enzyme $\alpha$-amylase used in starch hydrolysis has an affinity constant $(K_m)$ value of $0.005 \: M$. To achieve one-fourth of the maximum rate of hydrolysis, the...

In a chemostat with a dilution rate of $0.8$ $h^{-1}$, the steady state biomass concentration and the specific product formation rate are $8 \textit{ mol m}^{-3}$ and $0....

The specific growth rate of a mold during exponential phase of its growth in a batch cultivation is $0.15 \: h^{-1}$. If the cell concentration at $30 \: h$ is $33\: g L^...

A sedimentation tank of height $100 \textit{ cm}$ is used in a conventional activated sludge process to separate a suspension of spherical shaped granular sludge biomass ...

A batch cultivation of $\textit{E. coli}$ follows zeroth order Monod’s growth kinetics. The cell growth is terminated when the residual dissolved oxygen concentration att...

Milk flowing through a stainless steel inner tube ($40 \textit{ mm}$ inner diameter) of double tube-type heater is to be heated from $10^\circ C$ to $85^\circ C$ by satur...

A bacterium produces acetic acid from ethanol as per the following reaction $$2CH_3CH_2OH+2O_2 \rightarrow 2CH_3COOH+2H_2O$$ The thermodynamic maximum yield of acetic aci...

Which of the following statements is $ALWAYS\; CORRECT$ about an ideal chemostat?Substrate concentration inside the chemostat is equal to that in the exit streamOptimal d...

Yeast biomass $\left ( C_{6}H_{10}O_{3}N \right )$ grown on glucose is described by the stoichiometric equation given below:$$C_{6}H_{12}O_{6}+0.48\:NH_{3}+3\:O_{2} \to 0...

Phenolic wastewater discharged from an industry was treated with Pseudomonas $sp$. in an aerobic bioreactor. The influent and effluent concentrations of phenol were $10,0...

In a cross-flow filtration process, the pressure drop $\left ( \Delta P \right )$ driving the fluid flow is $2$ atm, inlet feed pressure $\left ( P_{i} \right )$ is $3$ a...