1. The Batch culture is a/an ______ culture system.
Explanation: The Batch culture is a closed culture system that contains an initial, limited amount of nutrients. The Continuous culture is an open system where nutrients are added continuously whereas the Fed-Batch culture is a semi-closed system.
2. A period during which the growth rate of cells gradually increases is known as _____
a) Lag phase
b) Log phase
c) Stationary phase
d) Deceleration phase
Explanation: A period during which the growth rate of cells gradually increases is known as a log or exponential phase. This is the period of maximum growth rate. This is usually the longest phase of the microbial growth period
3. During batch culture/fermentation, nutrients in the fermenter are utilized at a fast rate.
Explanation: In batch culture, the nutrients in the fermenter are added only once and are utilized by microbes at a slow rate whereas, in continuous culture, the nutrients in the fermenter are utilized at a very fast rate.
4. The exponential phase may be described by the equation ______
a) dx/dt = µx
b) dt/dx = µ
c) dx/dt = µt
d) dx2/dt2 = µ
Explanation: The exponential phase is described by equation,
dx/dt = µx
Where, x is concentration of microbial biomass, t is time in hours and µ is the specific growth rate, in hours-1.
5. During batch fermentation, in which phase the microbes in the fermenter are adapting to the new environment?
a) Lag phase
b) Log or exponential phase
c) Stationary phase
d) Death phase
Explanation: Microbes in the fermenter show lag phase when they are introduced in the fermenter where they adapt themselves for a particular environment. This is the phase where microorganisms prepare themselves and produce necessary enzymes or the metabolites necessary for their growth.
6. Who first suggested that filamentous fungi have a ‘growth unit’ which is replicated at a constant rate?
Explanation: Plomley (1959) was the first to suggest that filamentous fungi have a ‘growth unit’ which is replicated at a constant rate and is composed of the apex of hypha and a short length of supporting hypha.
7. Which of the following organisms represent the highest specific growth rate, µmax?
a) Vibrio natriegens
b) Methylomonas methanolytica
c) Aspergillus nidulans
d) Penicillium chrysogenum
Explanation: Vibrio natriegens represents the highest specific growth rate with µmax=4.24h-1 whereas, other organisms have a value between 0 to 1.
8. The size of fermenters is usually large in batch fermentation.
Explanation: The size of fermenters is larger as batch culture is mostly utilized of large-scale production and has therefore huge application in industrial production. The larger the size of the fermenter greater number of active microorganism can be added.
9. The Yield factor (Y) is the measure of the efficiency of _______
a) Conversion of anyone substrate into biomass
b) Conversion of all the substrates into biomass
c) The Affinity of an enzyme to the substrate
d) Number of microbes which produced the biomass
Explanation: The Yield factor (Y) is the measure of the efficiency of conversion of anyone substrate into biomass and it can be used to predict substrate concentration required to produce certain biomass.
10. The Yield Factor (Y) does not vary upon which of the following?
b) Growth rate
d) Amount of enzyme
Explanation: Yield factor varies on the growth rate, pH, temperature, the limiting substrate and the concentration of the substrate in excess. It does not depend on the amount of enzyme which is added for catalyzing the reaction.