What is the primary by-product of yeast fermentation?

• A) Methane
• B) Oxygen
• C) Carbon dioxide
• D) Nitrogen

What factor(s) may contribute to a bacterial population reaching the stationary phase?

• A) Logarithmic growth
• B) Exhaustion of required nutrients
• C) Synthesis of DNA
• D) Rapid reproduction

What gases can replace oxygen in the fermentation vessel during anaerobic fermentation?

• A) N2, CO2, or another by-product
• B) Methane and Hydrogen
• C) N2 and O2
• D) CO2 and O2

What is the principle behind using a spectrophotometer to measure bacterial growth?

• A) Optical density is constant for all bacterial cultures
• B) More light passes through turbid solutions
• C) Optical density is inversely proportional to cell density
• D) Turbidity is directly proportional to cell density

What is a characteristic of the death phase in bacterial growth?

• A) No further divisions occur
• B) Logarithmic increase in bacterial biomass
• C) Preparation for reproduction
• D) Synthesis of inducible enzymes

What is measured to estimate the numbers of bacterial cells in the spectrophotometer procedure?

• A) Wavelength
• B) Turbidity
• C) Incubation temperature
• D) Optical density

Which phase is sometimes referred to as the "exponential phase" of bacterial growth?

• A) Stationary phase
• B) Death phase
• C) Log phase
• D) Lag phase

What is the stationary phase also known as?

• A) Log phase
• B) Death phase
• C) Exponential phase
• D) Plateau phase

When does the stationary phase occur in the bacterial growth curve?

• A) After the lag phase
• B) When a required nutrient is exhausted or inhibitory end products accumulate
• C) During DNA synthesis
• D) Following the death phase

What is the basic principle involved in partition chromatography?

• A) Gravitational separation
• B) Magnetic attraction
• C) Centrifugal force
• D) Continuous partition between stationary and mobile phases

Which type of biological assay involves assessing the effect of a fermentation product on the growth and metabolic activities of test organisms?

• A) Diffusion assays
• B) Enzymatic assays
• C) Metabolic response assays
• D) Turbidimetric assays

What is used as a blank in the spectrophotometer procedure?

• A) Un-inoculated LB broth
• B) Culture solution
• C) Inoculated LB broth
• D) Bacterial cells

What happens during the log phase of bacterial growth?

• A) The growth rate equals the death rate
• B) Bacteria prepare for reproduction
• C) Maximum bacterial population is reached
• D) Rapid increase in bacterial number

What is the primary consideration for selecting the recovery and purification process in industrial fermentation?

• A) Cost-effectiveness
• B) All of the above
• C) Stability of the product
• D) Speed and simplicity

What is a crucial characteristic of a microorganism employed in a biological assay?

• A) Anaerobic nature
• B) Genetic stability
• C) Pathogenicity
• D) Complex growth requirements

What characterizes the log phase in the bacterial growth curve?

• A) Maximum bacterial number
• B) Rapid increase in bacterial number
• C) Synthesis of DNA
• D) Death rate equals the growth rate

Which stage involves the removal of large solid particles and microbial cells in the recovery of an extracellular product?

• A) Chromatography
• B) Filtration or centrifugation
• C) Fractionation
• D) Precipitation

Who did produce anaerobiosis by boiling the medium for cultivation?

• A) T.A. Brown
• B) Robert Hook
• C) Alexander Flemming
• D) Louis Pasteur

What is expected to happen to the balloons on the bottles after leaving the assembly for 24 hours during ethanol fermentation?

• A) Remain unchanged
• B) Deflate
• C) Burst
• D) Expand

What type of microorganisms are yeasts?

• A) Fungi
• B) Plants
• C) Bacteria
• D) Animals