Bioprocess Engineering

Correct answer: C. To ensure their quality and suitability

Raw material quality affects cell growth and product formation. For exams connect it with upstream quality control.

Correct answer: A. Membrane filtration

Heat sensitive substances can be sterilized by filtration. For exams connect filter sterilization with heat sensitive materials.

Correct answer: B. To help enzyme activities in small amounts

Trace elements are needed in small amounts and support cell functions. For exams remember them as micronutrients.

Correct answer: A. To fulfill cofactor and growth factor needs of cells

The direct answer is A: fulfilling the cofactor and growth-factor needs of cells. A culture medium supplies energy, carbon, nitrogen, minerals, water, and sometimes special organic nutrients. Some cells cannot make all vitamins themselves, or they need vitamins as parts of coenzymes that help enzymes perform chemical reactions. Adding the required vitamin can therefore support metabolism, cell division, and product formation. Option A is correct because it identifies the nutritional and biochemical role of vitamins. Option B is wrong because vitamins do not transform a liquid medium into metal. Option C is wrong because vitamins are nutrients and are not added to break a fermenter. Option D is wrong because vitamins do not stop air; aeration is controlled by equipment and process conditions. The memory cue is: vitamins are small but essential helpers of enzymes and growth, not construction materials or air barriers.

Correct answer: B. It may contain undefined components such as yeast extract

A complex medium has some components that are not fully defined. For exams distinguish it from defined medium.

Correct answer: A. A medium in which all chemical components and amounts are known

In a defined medium every component is clearly known. For exams remember it as chemically known medium.

Correct answer: C. Amount of cell growth

Biomass measurement shows the amount of cell material in culture. For exams connect it with growth monitoring.

Correct answer: B. To estimate cell mass

Dry weight gives a simple quantitative estimate of cell mass. For exams remember it as a biomass measurement method.

Correct answer: A. To indirectly estimate cell growth

Higher turbidity generally indicates more cells. For exams remember turbidity as indirect growth measurement.

Correct answer: C. Grown microbial colonies

Plate count is based on colonies formed by living cells. For exams connect it with viable cell counting.

Correct answer: A. Increased risk of strain change or contamination

Repeated transfer may affect culture purity. For exams connect culture preservation with stability.

Correct answer: B. To preserve cells or microbes at very low temperature

Cryopreservation helps preserve cultures for a long time. For exams remember it as low temperature preservation.

Correct answer: A. It can be preserved in dry form for a long time

Lyophilization removes moisture and can improve culture stability. For exams connect it with freeze dry preservation.

Correct answer: A. To improve productivity or traits of a microorganism

An improved strain may give more product or better traits. For exams connect it with increased industrial production.

Correct answer: A. To find better producing strains

Some mutations can improve production ability. For exams connect mutant selection with strain improvement.

Correct answer: A. Amount of product formed in a given time

In a bioprocess, productivity describes the rate or capacity of product formation over a specified period. In a simple expression, productivity can be represented as product formed divided by the relevant time, although industrial definitions may also relate it to reactor volume or biomass. Thus, if two runs make the same amount but one finishes sooner, the faster run has higher time-based productivity. Option A is correct because it connects production with a defined time interval. The color of the fermenter, sound of the medium, and shine of packaging do not measure biological or process output, so options B, C, and D are irrelevant distractors.

Correct answer: A. Product formation per cell or per biomass

Specific productivity shows production ability at cell level. For exams connect it with biomass based production.

Correct answer: B. Molecular charge

Ion exchange chromatography uses difference in charge. For exams remember the basis of chromatography methods.

Correct answer: A. On the basis of size

Gel filtration separates large and small molecules by size. For exams also remember it as size exclusion.

Correct answer: A. Purification based on specific binding

Affinity chromatography uses specific binding ability of the target molecule. For exams remember it as a highly selective method.

Correct answer: A. To change buffer or remove small solutes

The direct answer is A: changing the buffer or removing small dissolved solutes. Diafiltration is a membrane-based downstream operation, commonly performed with ultrafiltration. The product is retained by the membrane while buffer and small solutes pass through. Fresh buffer is added as filtrate leaves, so unwanted salts or small molecules are washed out and the product becomes equilibrated in the new buffer. Option A is correct because these are the main uses of diafiltration. Option B is wrong because coloring a fermenter is unrelated to membrane separation. Option C is impossible and irrelevant; air cannot be made into metal by diafiltration. Option D is wrong because the process does not name cells; identification is done by records or analytical methods. A useful cue is: ultrafiltration concentrates, while diafiltration washes and exchanges buffer, although both may be used together.

Correct answer: A. To remove cells and particles from liquid

Clarification can be an early separation step in downstream processing. For exams connect it with filtration or centrifugation.

Correct answer: A. Cell free upper liquid after centrifugation

Supernatant may contain dissolved extracellular products. For exams remember it as the liquid obtained after centrifugation.

Correct answer: A. Solid cells or particles settled at the bottom

After centrifugation heavy particles form a pellet at the bottom. For exams remember the difference between pellet and supernatant.

Correct answer: A. To increase final recovery and profit

Direct answer: Option A is correct. In a bioprocess, product recovery usually involves several downstream steps such as separation, purification and formulation. Product can be lost during transfer, filtration, extraction, purification or storage. Reducing these losses means that a larger fraction of the product originally made by the cells reaches the final usable form. This raises recovery and usually improves economic return or profit, assuming quality and costs are also managed. Option A states this correctly. Option B is wrong because contamination is unwanted and can make the product unsafe or unusable; it does not improve recovery. Option C is wrong because spoiling the medium damages the process and may reduce product quality. Option D is wrong because breaking the fermenter is equipment failure, not a method of improving production. The reasoning is simple: less loss means more product recovered; more recovered product generally means better yield and value. “Usually” is important because profit also depends on operating costs and selling price. Memory cue: downstream efficiency protects the product made upstream.