Bioprocess Engineering

Correct answer: B. To obtain high and stable product formation

A suitable strain can give more stable product output. For exams connect strain selection with production efficiency.

Correct answer: A. To prepare active cells for main fermentation

Seed culture provides active cells to start the main process. For exams remember it as inoculum preparation.

Correct answer: C. To remove microbes from incoming air

The governing concept is aseptic processing and contamination prevention. Aerobic cultures require air, but untreated incoming air can carry bacteria, fungal spores or other unwanted organisms. A suitable air filter removes or retains these contaminants before the air enters the fermenter, helping maintain a sterile or low-contamination environment. Therefore option C is correct. The filter does not sweeten the medium, freeze the product or colour the vessel. Sterile air is especially important when the desired production organism must grow without competition and when the product must meet quality and safety requirements. Filtration supports sterility, although it works together with sanitation, sterilisation and controlled operation.

Correct answer: D. To reduce vortex and improve mixing

Baffles reduce unwanted vortex and improve mixing. For exams connect baffles with mixing control.

Correct answer: A. To control temperature

A cooling jacket removes excess heat and controls temperature. For exams remember it as a temperature control device.

Correct answer: B. To take samples for testing during the process

A sampling port allows clean collection of culture samples. For exams connect it with process monitoring.

Correct answer: C. To monitor internal pressure

A pressure gauge helps in safe operation of the system. For exams connect it with safety and control.

Correct answer: D. To remove produced gases

An exhaust gas line removes gases from a fermenter in a controlled way. For exams remember it as part of the aeration system.

Correct answer: A. Amount of oxygen dissolved in the medium

The direct answer is A: the amount of oxygen dissolved in the medium. A dissolved oxygen, or DO, probe detects oxygen available in the liquid phase of a bioreactor, usually as a concentration or percentage of air saturation. This is important because aerobic cells need oxygen for respiration and growth. The probe sends a signal to the control system, which may adjust stirring or air supply when oxygen becomes too low. Option A is correct because it states exactly what the probe measures. Option B is wrong: fermenter height is measured by physical dimensions or a level instrument, not a DO probe. Option C is wrong: the product name is recorded as information and cannot be measured by this sensor. Option D is wrong: sound is measured by an acoustic instrument, not by an oxygen probe. A helpful exam cue is to connect DO with aerobic culture, aeration, and agitation; it is not a measurement of vessel size or product identity.

Correct answer: A. To measure acidity or alkalinity of the medium

A pH probe shows acidity level and helps control it. For exams connect pH with enzyme activity.

Correct answer: A. To improve cell growth and product yield

Optimized medium gives proper nutrients and can increase yield. For exams connect medium optimization with better production.

Correct answer: B. Raw nutrient used by microorganism

A substrate is used by cells and helps product formation. For exams remember it as raw material.

Correct answer: A. Reduction of cell growth or enzyme activity due to product

Some products can slow the process when present in high amount. For exams remember it as a yield control problem.

Correct answer: A. To reuse cells in the process

Immobilized cells remain attached to a support and can be reused. For exams connect it with cost reduction.

Correct answer: A. An enzyme attached to a support

An immobilized enzyme is attached to a support and can be used many times. For exams connect it with industrial enzyme use.

Correct answer: A. It may contain immobilized cells or enzymes packed on support

In a packed bed liquid can pass through immobilized biological material. For exams connect it with immobilized enzyme processes.

Correct answer: C. By circulation of liquid due to air flow

In an airlift bioreactor air moves the liquid up and down. For exams remember it as a system with lower mechanical damage.

Correct answer: A. The medium is mixed by an impeller

A stirred tank uses an impeller for mixing and oxygen distribution. For exams remember it as a common industrial bioreactor.

Correct answer: A. Damage to sensitive cells

High shear stress can break delicate cells. For exams remember the balance between mixing and cell safety.

Correct answer: A. To keep conditions within set limits

A control system keeps conditions such as temperature and pH stable. For exams connect it with safe and consistent production.

Correct answer: A. Cells adapt to the new environment

In lag phase cells adapt before active growth. For exams consider it the initial preparation phase.

Correct answer: B. Rapidly at a regular rate

In exponential phase cells divide rapidly. For exams remember it as the highly active growth phase.

Correct answer: A. Because nutrients decrease and waste increases

In stationary phase new cell formation and death may nearly balance. For exams remember nutrient limitation as a reason.

Correct answer: A. Number of living cells decreases

In death phase living cells decrease due to unfavorable conditions. For exams remember it as the final part of the growth curve.

Correct answer: A. किसी कोशिका जनसंख्या में जीवित कोशिकाओं का अनुपात

Cell viability is the proportion or percentage of living cells in a cell population. Only viable cells can grow and contribute to the formation of the desired biological product. The rate of product formation may be affected by viability, but it is not the definition of viability. Exam tip: associate viability with the percentage of living cells.