13 Questions N301: Mid-Semester Test 2000 Could Be About 40 Questions with 1 Min for Each

@13 Questions N301: Mid-Semester Test 2000 Could be about 40 questions with 1 min for each. Could be simple-medium-advanced for each topic. Topics could include: oxidation states. stoichiometry. kinetics. thermodynamics. water. sugar. fats. Would make 7 times 3 is 21. Say 3 on sugars and fats would be 11 times 3 is 33 looks OK. Other categories could include: Comprehension. Facts. Problems solving

@1 Oxygen Transfer OK

2Cs) The relationship between the oxygen transfer rate and the oxygen concentration (cL) is as follows: The OTR…
is independent of the dissolved oxygen concentration.
No. The oxygen transfer rate is in fact linearly correlated to the dissolved oxygen concentration. The correlation coefficient is the kLa value.
increases linearly with increasing oxygen concentration.
No with lots of oxygen already being in solution it becomes harder for more oxygen to dissolve. The driving force (saturation deficit) becomes less and less.
#decreases linearly with increasing oxygen concentration.
This is because increasing oxygen concentrations result in less driving force (saturation deficit) of the
increases exponentially with increasing oxygen concentration.
No.
decreases exponentially with increasing oxygen concentration.
No.
No.
No.
No.

@2 OUR OK

4Cs) A bioreactor with a kLa of 50 h-1 with active microbes is aerated resulting in a steady oxygen concentration of 2 mg/L. What is the microbial oxygen uptake rate (in mg/L/h) assuming the oxygen saturation concentration is 8 mg/L?
#300
Correct, at steady state the OUR = OTR
400
No.
200
No.
80
No.
800
No.
500
No.
600
No.
125
No.

@3 Effect of additives to chemostat

5Cs) A chemostat was run at steady state conditions, then one drop of a chemical solution was added, resulting in an immediate of the oxygen concentration from 2 to zero and an increase back to 2 over the next two minutes. The drop…
#contained a readily degradable electron donor for the culture.
Correct. The electron donor is responsible for extra OUR and a drop in DO
contained a compound that inhibits growth
No.
caused the death of the culture and washout according to the dilution rate.
No.
Contained readily usable electron acceptor for the culture
No, oxygen is the electron acceptor.
contained an oxygen absorbing compound such as bicarbonate
No.
contained an oxygen releasing compound such as sulfate
No.
Caused a temporary drop of the oxygen uptake rate (OUR)
No.
No.

@4 Oxygen Uptake OK

6Cs) If microbes in a constantly aerated bioreactor suddenly increase their respiration activity (OUR) this will affect the oxygen transfer in the following way: It will…
#increase OTR and decrease cL.
If the OUR increases this will result in OUR > OTR and thus a drop in cL. As a consequence of a decreasing dissolved oxygen concentration (cL) the OTR will improve (higher driving force = saturation deficit = (cS-cL)).
decrease OTR. and cL.
No.
decrease OTR and increase cL.
No.
increase OTR and and cL.
No.
increase kLa and OTR.
No.
decrease kLa and increase OTR.
No.
No.
No.

@5 Calculate kLa OK

11Ps) The airflow to a chemostat running at steady state DO of 2 mg/L (cs was 8 mg/L) was temporarily interrupted. The oxygen concentration decreased steadily by 0.1 mg/L every second. What is the kLa of the chemostat in h-1 ?
#60
kLa = OTR /(cs –cL). Thus kLa = 100 mg/L * (8-5 mg/L) = 100mg/L/h / 5 mg/L = 20 h-1.
200
No.
20
No
50
No.
500
No.
0.2
No.
0.6
No.
1
No.

@6 Calculate kLa OK

11Ps) A reactor
#60
kLa = OTR /(cs –cL). Thus kLa = 100 mg/L * (8-5 mg/L) = 100mg/L/h / 5 mg/L = 20 h-1.
200
No.
20
No
50
No.
500
No.
0.2
No.
0.6
No.
1
No.

@7 Oxygen requirment OK

11Ps) How much oxygen (mol) is necessary for the complete oxidation of the following molecule to CO2 : CH3-CHOH-CH2-COOH
#4.5
kLa = OTR /(cs –cL). Thus kLa = 100 mg/L * (8-5 mg/L) = 100mg/L/h / 5 mg/L = 20 h-1.
6
No.
9
No
4
No.
2.5
No.
7
No.
3.5
No.
5
No.

@8 Oxygen Uptake OK

6Cs) In order to increase the steady state concentration of biomass in an aerobic culture in a chemostat, would you…
#increase the substrate concentration in the reservoir .
Yes.
increase the dilution rate, thereby increasing u.
No.
increase the medium flow rate.
No.
decrease the airflow rate.
No.
No.
No.
No.
No.

@9 Oxygen Uptake OK

6Cs) Two different species are available for chemostat culture which are identical except that A has a higher Ymax than B. What effect the difference in Ymax have on the steady state characteristics of the chemostat?
#A would have a higher steady state biomass concentration at all dilution rates.
Yes.
A would be able to operate at higher dilution rates than B.
No.
B would have a higher critical dilution rate than A.
No.
A would have a higher steady state biomass concentration at high dilution rates than B.
No.
The residual substrate concentration would be higher in A than in B.
No.
No.
No.
No.

@10 Electron carriers OK

11Ps) How much NADH can be produced from the conversion of ethanol (CH3-CH2OH) to acetic acid (CH3-COOH)
#2
kLa = OTR /(cs –cL). Thus kLa = 100 mg/L * (8-5 mg/L) = 100mg/L/h / 5 mg/L = 20 h-1.
4
No.
1
No
3
No.
6
No.
7
No.
3.5
No.
5
No.

@11 Electron equivalents OK

11Ps) In the acetone butanol fermentation butyrate (C4 fatty acid) is the electron acceptor of how many electrons when reduced to butanol (C4 alcohol).
#4
kLa = OTR /(cs –cL). Thus kLa = 100 mg/L * (8-5 mg/L) = 100mg/L/h / 5 mg/L = 20 h-1.
2
No.
1
No
3
No.
5
No.
6
No.
8
No.
12
No.

@12 Electron equivalents OK

11Ps) Reduced electron carriers (e.g. NADH) …
#a problem to many anaerobic organisms, if they can’t reoxidise them
yes
are the principal energy source to all organisms
No.
useful only to anaerobic organisms
No
represent a major metabolic problem to aerobic organisms
No.
directly operate the ATP-synthase reaction
No.
can always be used to produce high levels of hydrogen gas in fermentations
No.
8
No.
12
No.

@13 Electron equivalents OK

11Ps) In the absence of oxygen, bacteria can use the oxygen contained in nitrate (NO3-) or in water (H2O) as an alternative electron acceptor
#Statement is incorrect as the oxygen in water and nitrate is already reduced
yes
Statement is correct for all bacteria
No.
Statement is correct for aerobic bacteria
No
Statement is correct for anaerobic bacteria
No.
Statement is correct for those bacteria that can use ferredoxin as electron carrier
No.
No.
No.
No.

@14 Oxygen

11Ps) The oxygen in water can be an electron donor in some biological reactions . This statement is…
#true for photosynthetic organisms which produce O2 as an endproduct.
yes
not true as the oxygen atom in the H2O molecule can not provide electrons because it is already in its most oxidised state
No.
true of all respiring bacteria using O2 as electron acceptor
No
No.
No.
No.
No.
No.

@15 Maintenance coefficient

11Ps) The bacterial maintenance coefficient is responsible for…
#loss in biomass concentration in the absence of an electron donor
yes
washout at high dilution rates in a chemostat
No.
oxygen limitation at low DO levels
No
the lag phase in batch cultures
No.
the low substrate concentrations typical for substrate limited chemostats
No.
No.
No.
No.

@16 Maintenance coefficient

11Ps) A bacterium with a very high half saturation constant (kS value) …
# is not suited to chemostat cultures where the substrate is limiting.
yes
is particularly suited to chemostat cultures where the substrate is limiting.
No.
will allow being grown in chemostats at very high dilution rate.
No
will allow high levels of growth in both chemostat and batch cultures.
No.
will allow low levels of growth in both chemostat and batch cultures.
No.
No.
No.
No.

@17 Chemostat

11Ps) In a chemostat the growth rate of bacteria can be lowered by about 50% by …
#decreasing the medium flow rate by 50%
yes
doubling the dilution rate.
No.
diluting the feed concentration by a factor 2
No
doubling the concentration of the feed concentration
No.
halving the DO concentration
No.
doubling the DO concentration
No.
running it at about twice the critical dilution rate
No.
No.