Agricultural/Bioengineering Bioprocess Engineering 3

Question 1

Which enzyme immobilization method traps enzymes within a polymer network (such as calcium alginate beads), allowing substrates and products to diffuse freely?

Accepted Answer

Gel entrapment

Answer

Gel entrapment physically encloses enzymes within a porous polymer matrix; the enzyme cannot escape, but small substrate and product molecules diffuse in and out to sustain catalysis.

Question 2

According to the Monod equation μ = μmax × S / (Ks + S), when substrate concentration S is much greater than Ks, the specific growth rate μ approaches:

Accepted Answer

μmax

Answer

When S >> Ks, the term S/(Ks + S) approaches 1, so μ approaches μmax — the organism grows at its maximum specific rate independent of further substrate increases.

Question 3

In a membrane bioreactor (MBR) used for wastewater treatment, what is the primary role of the membrane module?

Accepted Answer

To physically retain biomass while allowing clarified effluent to permeate

Answer

The membrane in an MBR acts as a physical barrier that holds back suspended solids and microorganisms while allowing treated water to pass through, replacing the secondary clarifier in conventional activated sludge systems.

Question 4

Which microorganism is most commonly used for commercial-scale lactic acid production through homolactic fermentation?

Accepted Answer

Lactobacillus delbrueckii

Answer

Lactobacillus delbrueckii and related homofermentative lactobacilli convert glucose almost exclusively to lactic acid via the Embden-Meyerhof-Parnas pathway, achieving high yields under anaerobic conditions.

Question 5

In thermal sterilization of fermentation media, the Del factor (∇) is used to quantify sterilization efficacy. What does ∇ represent mathematically?

Accepted Answer

Natural logarithm of the ratio of initial spore count to final spore count

Answer

The Del factor ∇ = ln(N₀/N) expresses the log reduction in viable spores; a ∇ of 12 means reducing contamination probability to 10⁻¹² — one chance in a trillion batches.

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Practice Test

Agricultural/Bioengineering Bioprocess Engineering 3