ICAR AICE-JRF/SRF (PhD) — Food Processing Technology, Food Safety & Quality, Processing and Food Engineering · India · ICAR through the National Testing Agency
Original practice questions written to the published syllabus · not past papersMicroorganisms and enzymes put to work: starter cultures, the microbiology of fermented foods, industrial fermenter design and operation, downstream recovery, and the modern biotechnology (recombinant enzymes, precision fermentation, single-cell protein) that is reshaping ingredients.
In the exams: GATE XE-G and XL-U Section 2 (fermented foods and beverages); ICAR AICE 35.a Unit 6 (food microbiology and biotechnology)
How our questions for ICAR AICE-JRF/SRF spread across the units of Fermentation Technology & Food Biotechnology. Difficulty: 8 easy, 31 medium, 12 hard.
| Batch, fed-batch and continuous fermentation kinetics | 10 | |
| Fermenter design, aeration and agitation | 9 | |
| Downstream processing: separation and purification of fermentation products | 8 | |
| Recombinant DNA technology and GM foods | 4 | |
| Precision fermentation and its regulation | 4 | |
| Starter culture production, preservation and bacteriophage control | 3 | |
| Production of food enzymes, organic acids, amino acids and flavours by fermentation | 3 | |
| Lactic acid bacteria, yeasts and moulds as starter cultures | 2 | |
| Fermented dairy foods: curd, yoghurt and cheese microbiology | 2 | |
| Single-cell protein and single-cell oil | 2 | |
| Fermented vegetables: sauerkraut, kimchi and pickles | 1 | |
| Fermented cereal and legume foods: idli, dosa, tempeh, miso and soy sauce | 1 | |
| Fermented meat and fish products | 1 | |
| Vinegar fermentation | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Nisin, a bacteriocin used as a food preservative, is produced by which organism and acts mainly against which bacteria?
A. Lactococcus lactis; Gram-positive bacteria including spore-formers
Nisin, a lantibiotic from some Lactococcus lactis strains, acts on the membranes of Gram-positive bacteria and inhibits outgrowth of spores of Clostridium and Bacillus. The outer membrane protects Gram-negative bacteria unless it is disrupted; nisin has no useful antifungal action.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
Why does rotating starter strains help control phage in a plant?
B. Phage built up on one strain cannot attack the next
Phages are usually host-specific; by alternating strains with different phage sensitivity, a phage population that rises against one strain finds no host in the next vats and declines. The other explanations are not the mechanism.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
What causes the eyes and sweet nutty flavour of Swiss-type cheeses?
A. Propionibacteria turning lactate into propionate, acetate and CO₂
Propionibacteria convert lactate into propionic and acetic acids and CO₂ during warm-room ripening, forming the eyes. Clostridial fermentation is the late-blowing defect; methyl ketones flavour blue cheese; Leuconostoc gives small openings in some Dutch-type cheeses.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
Why do industrial vinegar processes stop or recharge before all ethanol is used?
A. Over-oxidation of acetic acid to CO₂ begins
With no ethanol left, over-oxidising strains oxidise acetic acid to CO₂ and water, losing product; a small residual ethanol is kept and fresh mash added. The other explanations are incorrect.
Further reading: Hutkins, Microbiology and Technology of Fermented Foods
Solid-state fermentation is used for koji and some fungal enzymes. What is its main engineering difficulty?
B. Removing heat and controlling moisture in the bed
With little free water, heat from mould respiration is hard to remove and temperature and moisture gradients form; this limits bed depth and scale. Substrates are moist, not submerged; foaming is a submerged-culture problem; koji moulds need oxygen.
Further reading: Stanbury, Whitaker and Hall, Principles of Fermentation Technology; Doran, Bioprocess Engineering Principles
In the Monod equation, what is Ks?
C. The substrate concentration at which μ = μmax/2
μ = μmax·S/(Ks + S); when S = Ks, μ = μmax/2. Ks is analogous to Km in enzyme kinetics. μmax is the maximum rate, Y the yield, and feed rate is an operating variable.
Further reading: Stanbury, Whitaker and Hall, Principles of Fermentation Technology; Doran, Bioprocess Engineering Principles
A chemostat has μmax = 0.5 h⁻¹, Ks = 0.2 g/L, feed substrate 10 g/L, yield 0.5 g/g and dilution rate 0.25 h⁻¹. What is the steady-state biomass?
C. 4.9 g/L
S = Ks·D/(μmax − D) = 0.2 × 0.25/0.25 = 0.2 g/L. X = Y(S_R − S) = 0.5 × (10 − 0.2) = 4.9 g/L. 5.0 ignores residual substrate; 2.5 multiplies by D; 9.8 forgets the yield.
Further reading: Stanbury, Whitaker and Hall, Principles of Fermentation Technology; Doran, Bioprocess Engineering Principles
A chemostat is run with dilution rate D. What happens if D exceeds the maximum growth rate attainable at the feed concentration?
D. The cells wash out of the vessel
At steady state μ = D; if D is greater than the highest μ the organism can reach, cells leave faster than they are produced and wash out, while substrate rises to the feed level. Biomass cannot rise without limit in a continuous flow.
Further reading: Stanbury, Whitaker and Hall, Principles of Fermentation Technology; Doran, Bioprocess Engineering Principles
Which chromatographic method separates proteins mainly by molecular size?
C. Gel filtration, also called size exclusion
In gel filtration, large molecules are excluded from the pores of the beads and elute first; small ones enter the pores and elute later. Ion exchange separates by charge, affinity by specific binding, and hydrophobic interaction by surface hydrophobicity.
Further reading: Stanbury, Whitaker and Hall, Principles of Fermentation Technology; Doran, Bioprocess Engineering Principles
How does CRISPR-Cas9 genome editing introduce a change at a chosen site?
D. A guide RNA directs Cas9 to cut there, and cellular repair makes the change
The guide RNA base-pairs with the target next to a PAM sequence, Cas9 makes a double-strand break, and non-homologous end joining (small insertions or deletions) or homology-directed repair with a template makes the edit. Random plasmid insertion and restriction digestion are not genome editing; T-DNA integration is not guided.
Further reading: Codex CAC/GL 44-2003 and related guidelines; Stanbury, Principles of Fermentation Technology
Ten here, 51 in the app. The Laisha app has every practice question we have written to ICAR AICE-JRF/SRF in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
An AI operating system for agriculture: free guides, manuals and tools written for every country.