Microbes in Human Welfare Set-2

Q1. During alcoholic fermentation by yeast, glucose is converted to ethanol according to the reaction $C_6H_{12}O_6 \rightarrow 2\,C_2H_5OH + 2\,CO_2$. Molar masses: glucose $=180\ \mathrm{g\,mol^{-1}}$, ethanol $=46\ \mathrm{g\,mol^{-1}}$. If $1000\ \mathrm{g}$ of glucose is fermented and the fermentation proceeds at $80\%$ of theoretical yield, the approximate mass of ethanol produced is:

Q2. A bacterial population of $10^9$ cells contains resistant mutants at a frequency of 1 per $10^6$ cells. A bactericidal antibiotic is applied that kills $99.999\%$ of susceptible cells but leaves resistant cells unaffected. Immediately after treatment, what percentage of the surviving population is expected to be resistant?

Q3. In a recombinant E. coli culture carrying a plasmid for insulin production, plasmid-free segregation occurs such that, in the absence of antibiotic selection, each generation $10\%$ of daughter cells lose the plasmid. Starting from a pure plasmid-bearing population, the fraction of cells that will still carry the plasmid after 10 generations is closest to:

Q4. Assertion (A): Bacillus thuringiensis (Bt) Cry proteins expressed in transgenic crops are toxic to specific insect pests but are generally non-toxic to mammals and most beneficial insects.
Reason (R): Cry protoxins require solubilization at alkaline pH and proteolytic activation in the insect midgut; the resultant active fragments bind to specific gut receptors present in susceptible insects but absent in mammals.

Q5. A subunit vaccine uses a pathogen surface glycoprotein produced recombinantly in E. coli. Clinical trials show reduced immunogenicity attributed to absence of native glycosylation on the antigen. Which modification to the production process is most likely to restore native glycosylation patterns and thereby improve antigenicity while remaining a practical approach for scalable vaccine manufacture?

Q6. In alcoholic fermentation by Saccharomyces cerevisiae the reaction is $C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2$. If 100 g of glucose is completely fermented, what is the theoretical maximum mass of ethanol produced? (Molar masses: glucose = $180\ \mathrm{g\;mol^{-1}}$, ethanol = $46\ \mathrm{g\;mol^{-1}}$.)

Q7. In single cell protein (SCP) production, yeast grown on molasses converts sugar to biomass with biomass yield coefficient $Y_{x/s}=0.6\ \mathrm{g\ biomass\;per\;g\ sugar}$. If 1000 kg of sugar is processed and the harvested yeast biomass contains 45% protein (w/w), what is the mass of protein produced (in kg)?

Q8. A coastal oil-contaminated site contains 12,000 kg of hydrocarbon with 85% carbon by mass. To stimulate microbial biodegradation the remediation team aims for a target carbon:nitrogen ratio of $100:5$ (w/w). How much elemental nitrogen (in kg) must be added to reach the target ratio?

Q9. A poultry farm uses tetracycline in feed; resulting manure contains antibiotic residues and a high load of tetracycline‑resistant bacteria and resistance genes (ARGs). Before applying this manure as fertiliser, which single treatment will most effectively reduce both viable resistant bacteria and the selection pressure from antibiotic residues, thereby minimising ARG dissemination into soil?

Q10. A chlorinated aromatic pollutant X is reductively dechlorinated under anaerobic conditions to a less‑chlorinated intermediate Y, but Y is biodegraded only under aerobic conditions. Which bioremediation strategy is most likely to achieve complete mineralisation of X in contaminated soil?