Bioprocess Engineering Flashcards
7 cards from real Agricultural/Bioengineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Bioprocess Engineering flashcards as text
In fed-batch fermentation, substrate is added incrementally rather than all at once. What is the primary reason for this feeding strategy?
Answer: To prevent substrate inhibition and maintain optimal growth conditions
Controlled substrate feeding in fed-batch fermentation prevents substrate inhibition by keeping the substrate concentration below inhibitory levels while sustaining cell growth and product formation.
What are the standard conditions for steam sterilization (autoclaving) of fermentation media?
Answer: 121°C for 15–20 minutes at 15 psi
The standard autoclave cycle at 121°C (250°F) and 15 psi for 15–20 minutes provides sufficient thermal energy to destroy all vegetative cells and spores.
The Reynolds number (Re) in a stirred bioreactor is primarily used to determine:
Answer: Flow regime (laminar vs. turbulent) within the vessel
Re = ρND²/μ for a stirred tank; low Re indicates laminar flow with poor mixing while high Re indicates turbulent flow with efficient bulk mixing.
Which microorganism is the primary industrial producer of citric acid through submerged fermentation?
Answer: Aspergillus niger
Aspergillus niger accounts for over 90% of global citric acid production by fermenting sucrose or glucose under nitrogen-limited, low-pH conditions.
During bioprocess scale-up from laboratory to industrial scale, which parameter is most commonly kept constant to preserve similar mixing and oxygen transfer characteristics?
Answer: Power input per unit volume (P/V)
Maintaining constant P/V (power per unit volume) preserves similar turbulence intensity, mixing time, and oxygen transfer rate, making it the most reliable scale-up criterion for stirred bioreactors.
What is the primary purpose of a dissolved oxygen (DO) probe in a bioreactor control system?
Answer: To monitor oxygen levels and trigger adjustments in aeration or agitation
DO probes provide real-time feedback to control systems that adjust airflow rate, agitation speed, or back-pressure to maintain adequate oxygen supply for aerobic fermentation.
In bioprocess engineering, 'aseptic technique' refers to the set of practices designed to:
Answer: Prevent contamination of pure microbial cultures by extraneous organisms
Aseptic technique encompasses all operational procedures — including sterilization, sterile connections, and laminar flow — that prevent contamination of the process culture by unwanted microorganisms.