ASRB NET and ARS Fermentation Technology & Dairy Biotechnology: practice questions

1 · Fermenter design and types of fermentation · medium

Lactic acid fermentations need simpler vessels than fungal enzyme fermentations mainly because they:

1. Need no aeration
2. Use no pH control
3. Produce no heat
4. Run at 121 °C

2 · Industrial production of lactic acid and other organic acids · medium

Whey permeate is supplemented with yeast extract or corn steep liquor for lactic acid fermentation because:

1. It neutralises the acid
2. It sterilises the medium
3. Permeate contains no carbohydrate the bacteria can use
4. Lactic acid bacteria are nutritionally demanding

3 · Industrial production of lactic acid and other organic acids · medium

In classical lactic acid recovery, acidifying calcium lactate with sulphuric acid produces:

1. Gypsum as a by-product
2. Ethanol as a by-product
3. Sodium chloride
4. Pure L-lactide

4 · Production of enzymes: beta-galactosidase, proteases, lipases · easy

Yeast lactase from Kluyveromyces lactis is suited to milk because its pH optimum is:

1. Strongly acid, 1–2
2. Strongly alkaline, above 10
3. Near neutral, 6.5–7
4. Acidic, 3.5–5

5 · Immobilised enzymes and continuous processes · medium

Glutaraldehyde is used in enzyme immobilisation as a:

1. Cross-linking agent
2. Substrate
3. Gel-forming polysaccharide
4. Adsorbent resin

6 · Immobilised enzymes and continuous processes · medium

The main operational problem of continuous immobilised-enzyme reactors treating milk is:

1. Lack of fat
2. Microbial contamination and fouling
3. Excess enzyme in the product
4. Too little lactose

7 · Recombinant DNA technology and genome editing of dairy microbes · medium

Which strain-improvement method gives products not regulated as GMOs?

1. Selection of spontaneous phage-resistant mutants
2. CRISPR insertion of a foreign gene into the chromosome
3. Plasmid with an E. coli gene
4. Transgenic expression of chymosin

8 · Precision fermentation of milk proteins · easy

Precision fermentation differs from biomass fermentation in that:

1. The cells themselves are the product
2. It is a traditional, spontaneous food fermentation process
3. No microorganism is used
4. The target is a protein purified from the culture

9 · Precision fermentation of milk proteins · medium

2'-Fucosyllactose for infant formula is produced commercially by:

1. Solid-state fermentation
2. Precision fermentation in engineered E. coli
3. Chemical synthesis from lactose alone, without enzymes
4. Extraction from human milk

10 · Precision fermentation of milk proteins · medium

Which yeast, formerly called Pichia pastoris, is a host for precision fermentation?

1. Debaryomyces hansenii
2. Saccharomyces boulardii
3. Kluyveromyces marxianus
4. Komagataella phaffii