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51.	Which sparger consist of a single open or partially-closed pipe providing a stream of air bubbles?(a) Perforated sparger(b) Orifice sparger(c) Nozzle sparger(d) Porous spargerThe question was posed to me in semester exam.Question is taken from Practical Considerations For Bioreactor Construction in section Reactor Engineering of Bioprocess Engineering
Answer» Correct choice is (c) NOZZLE sparger Easy EXPLANATION: Nozzle spargers are used in many agitated fermenters from laboratory to production scale. These spargers consist of a single open or partially-closed pipe PROVIDING a stream of air BUBBLES.

52.	Mixing is usually better in external-loop than internal-loop reactors in air-lift reactors.(a) True(b) FalseI have been asked this question during an interview for a job.Asked question is from Bioreactor Configurations topic in division Reactor Engineering of Bioprocess Engineering
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53.	For an ideal plug flow, Reynolds number should be ____________(a) Low(b) Variably low(c) High(d) Not very highThe question was asked in an online interview.My question is taken from Sterilisation topic in portion Reactor Engineering of Bioprocess Engineering
Answer» The correct ANSWER is (c) HIGH To ELABORATE: Plug flow is approached in pipes at turbulent Reynolds numbers above about 2 × 10^4; operation at high Reynolds numbers minimises FLUID mixing and velocity VARIATION.

54.	For smaller vessels, which type of sealing is required between the gap of fermenter and the stirrer?(a) Mechanical seal(b) Double-mechanical seal(c) Magnetic seal(d) Non-magnetic sealI have been asked this question during an internship interview.My enquiry is from Practical Considerations For Bioreactor Construction in section Reactor Engineering of Bioprocess Engineering
Answer» The correct choice is (c) Magnetic seal The BEST explanation: On smaller vessels, magnetic drives can be used to couple the stirrer shaft with the MOTOR; with these devices, the shaft does not PIERCE the fermenter body. A magnet in a housing on the outside of the fermenter is driven by the stirrer motor; inside, another magnet is ATTACHED to the end of the stirrer shaft and held in place by bearings. Sufficient power can be TRANSMITTED using magnetic drives to agitate vessels up to at least 800 litres in size.

55.	Positive pressure is the pressure in which air flows only inside.(a) True(b) FalseThis question was posed to me by my school principal while I was bunking the class.Enquiry is from Practical Considerations For Bioreactor Construction in portion Reactor Engineering of Bioprocess Engineering
Answer» The correct ANSWER is (B) False The explanation is: In Positive pressure air or gas pressure is greater than that of the atmosphere. Air will flow out of the room INSTEAD of in, so that any airborne microorganisms (e.g., bacteria) does not contaminate the ENVIRONMENT in the bioreactor.

56.	Mechanical foam breaker is generally preferred over antifoam agents.(a) True(b) FalseThis question was posed to me by my school principal while I was bunking the class.Enquiry is from Bioreactor Configurations in portion Reactor Engineering of Bioprocess Engineering
Answer» Right option is (a) True Explanation: If foaming is a PROBLEM, a supplementary impeller CALLED a foam breaker may be installed. Alternatively, chemical ANTIFOAM agents are added to the broth; because antifoams reduce the rate of oxygen transfer, MECHANICAL foam dispersal is GENERALLY preferred.

57.	The pores of filter for filtration should be between in diameter is _________(a) 0.1 – 0.55 μm(b) 0.2 – 0.45 μm(c) 0.3 – 0.45 μm(d) 0.3 – 0.50 μmThis question was posed to me in an online interview.Asked question is from Sterilisation in section Reactor Engineering of Bioprocess Engineering
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58.	Glass fermenters is used for about _____(a) 50 litres capacity(b) 100 litres capacity(c) 300 litres capacity(d) 30 litres capacityI had been asked this question in my homework.The question is from Practical Considerations For Bioreactor Construction in chapter Reactor Engineering of Bioprocess Engineering
Answer» Right choice is (d) 30 litres CAPACITY Best explanation: Glass is USED to CONSTRUCT fermenters up to about 30 litres capacity. The ADVANTAGES of glass are that it is smooth, non-toxic, corrosion-proof and transparent for easy inspection of the vessel contents.

59.	Which of the following type is of the perfusion culture?(a) Batch(b) Conc. Batch(c) Continuous(d) Conc. Fed-BatchThe question was posed to me in examination.Origin of the question is Ideal Reactor Operation in portion Reactor Engineering of Bioprocess Engineering
Answer» The CORRECT ANSWER is (d) Conc. Fed-Batch For EXPLANATION: Concentrated Fed-Batch- In a process that can be considered a form of perfusion, the culture is perfused to generate ultrahigh cell concentration, GREATER than 10^8 cells/mL; and the product is also retained in the vessel.

60.	Respiratory quotient has no units.(a) True(b) FalseI had been asked this question in a job interview.I want to ask this question from Monitoring and Control of Bioreactors in division Reactor Engineering of Bioprocess Engineering
Answer» RIGHT answer is (a) True Explanation: The respiratory quotient (or RQ or respiratory COEFFICIENT), is a dimensionless number used in calculations of basal METABOLIC rate (BMR) when estimated from carbon dioxide production. It is calculated from the ratio of carbon dioxide produced by the body to oxygen CONSUMED by the body. Such measurements, like measurements of oxygen uptake, are forms of indirect calorimetry.

61.	What is proportional-integral-derivative (PID)?(a) Bioreactor(b) Controller(c) Mathematical integration(d) Mathematical differentiationI had been asked this question in an interview for internship.The above asked question is from Monitoring and Control of Bioreactors in division Reactor Engineering of Bioprocess Engineering
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62.	The vessel should have the minimum number of internal structures.(a) True(b) FalseI have been asked this question during an online exam.The doubt is from Practical Considerations For Bioreactor Construction topic in portion Reactor Engineering of Bioprocess Engineering
Answer» The correct answer is (a) True The best explanation: Industrial fermenters are designed for in SITU steam sterilisation under pressure. The vessel should have a minimum number of internal structures, ports, nozzles, connections and other ATTACHMENTS to ensure that steam reaches all parts of the EQUIPMENT. For effective sterilisation, all air in the vessel and PIPE connections must be DISPLACED by steam.

63.	Which of the following is the function of draft tube?(a) Decrease the pressure(b) Increase the velocity(c) Maximize kinetic energy(d) Minimize kinetic energyThe question was asked in my homework.I want to ask this question from Bioreactor Configurations in portion Reactor Engineering of Bioprocess Engineering
Answer» Right option is (c) MAXIMIZE kinetic ENERGY To EXPLAIN I would say: The draft TUBE is a conduit which connects the runner exit to the tail race where the water is being finally discharged from the turbine. The primary function of the draft tube is to reduce the velocity of the discharged water to minimize the loss of kinetic energy at the outlet. This draft tube at the end of the turbine increases the pressure of the exiting fluid at the expense of its velocity. This means that the turbine can reduce pressure to a higher extent WITHOUT fear of back flow from the tail race.

64.	Zymomonas mobilis is used to convert glucose to ethanol in a batch fermenter under anaerobic conditions. The yield of biomass from substrate is 0.06 g g^-1; YPX is 7.7 g g^-1. The maintenance coefficient is 2.2 g g^-1 h^-1; the specific rate of product formation due to maintenance is 1.1 h^-1. The maximum specific growth rate of Z. mobilis is approximately 0.3 h^-1.5 g bacteria are inoculated into 50 litres of medium containing 12 g l^-1 glucose. Determine batch culture times required to produce 10 g biomass.(a) 3.1 h(b) 3.3 h(c) 3.5 h(d) 3.7 hI had been asked this question by my school principal while I was bunking the class.The question is from Ideal Reactor Operation in portion Reactor Engineering of Bioprocess Engineering
Answer» Right option is (d) 3.7 h To ELABORATE: Yxs = 0.06 gg^-l; Ypx= 7. 7 gg^-l; μmax = 0. 3 h^-l; ms=2.2 gg^-l h^-l; mp= 1.1 h^-l; x0=5g/501= 0.1 gl^-l;s0= 12 gl^-l. If 10 G BIOMASS are produced by reaction, the final amount of biomass present is (10 + 5) g = 15 g. Therefore xf = 15 g / 50 l = 0.3 g l^-1.

65.	What is an MPR rating on air filters?(a) Magnitude performance rating(b) Micro-particle performance rating(c) Macro-particle performance rating(d) Moles per rateThe question was asked in semester exam.This is a very interesting question from Sterilisation topic in division Reactor Engineering of Bioprocess Engineering
Answer» RIGHT choice is (b) Micro-particle performance RATING To explain: MPR (Micro-Particle Performance Rating) MPR Rating is a rating SYSTEM developed by 3M. It rates the manufacturer’s filters and their ABILITY to capture AIRBORNE particles smaller than 1 micron.

66.	Microcarrier beads can be used in __________(a) Fluidized-bed(b) Stirred vessel(c) Packed-bed(d) Trickle-bedI had been asked this question during an internship interview.I'd like to ask this question from Bioreactor Configurations in chapter Reactor Engineering of Bioprocess Engineering
Answer» CORRECT choice is (a) Fluidized-bed For explanation: Fluidised beds can also be used with MICROCARRIER beads used in attached animal CELL culture. Fluidised-bed microcarrier cultures can be operated both in BATCH and continuous mode. In the FORMER the fermentation fluid is recycled in a pump-around loop.

67.	Neural network process includes ___________(a) Constant behavior(b) Transient behavior(c) Stationary behavior(d) Immobile behaviorThe question was posed to me in quiz.I would like to ask this question from Monitoring and Control of Bioreactors in chapter Reactor Engineering of Bioprocess Engineering
Answer» Right option is (b) Transient behavior Easy explanation: Information about FEED flow rate and substrate and BIOMASS concentrations as a function of time can be used to develop a NEURAL NETWORK for analysis of transient behaviour in continuous fermentation which is able to PREDICT future changes in substrate and cell concentrations.

68.	Electro polishing is also referred as _________(a) Anodic polishing(b) Cathodic polishing(c) Electron polishing(d) Non-ionic polishingThis question was posed to me in homework.This interesting question is from Practical Considerations For Bioreactor Construction in chapter Reactor Engineering of Bioprocess Engineering
Answer» Right choice is (a) Anodic polishing Explanation: Electropolishing, also known as ELECTROCHEMICAL polishing, anodic polishing or electrolytic polishing (especially in the METALLOGRAPHY field), is an electrochemical process that REMOVES MATERIAL from a metallic workpiece. It is used to polish, passivate, and deburr metal parts. It is often described as the reverse of electroplating.

69.	For high viscous fluids, air-driven reactors are preferred over stirred vessels.(a) True(b) FalseI had been asked this question in class test.This key question is from Bioreactor Configurations in portion Reactor Engineering of Bioprocess Engineering
Answer» Right choice is (b) False For EXPLANATION: If the culture has high viscosity, sufficient mixing and mass transfer cannot be provided by air-driven reactors. Stirred vessels are more SUITABLE for VISCOUS liquids because greater power can be input by mechanical AGITATION. Nevertheless, mass- transfer rates decline rapidly in stirred vessels at VISCOSITIES greater than 50-100 cP.