Olav Flashcards
An aerated batch bioreactor with wastewater containing a diverse bacterial
community and the substrates ammonia and organic matter is run until all
substrates are consumed.
a. Which substrate will be consumed first – and why?
b. What are the oxidized forms of the electron donors and what is the
reduced form of the electron acceptor at the end of the batch
experiment?
a) The organic substrate will be consumed first, as the energy yield is higher for this consumption in the aerobic consitions which allow it.
b) The aerobic respiration of ammonia is denitrification, where ammonium is first oxidized to nitrite, which is gurther oxidized to nitrate. The oxidized substrate is also the electron donor. The reduced form of the electron donor is ammonium, and the oxidized form is nitrite in the first half-reaction. In the second half reaction, the reduced form is nitrite and the oxidized form is nitrate.
For the organic reaction, glucose is oxidized to CO2, meaning that glucose is the reduced form of the electron donor and CO2 is the oxidized form.
. Municipal wastewater is treated in a flow-through system based on aerobic
heterotrophic degradation. Why is biomass retention required for a successful
process, and what is the strategy for biomass retention in the traditional
process for biological treatment of municipal wastewater treatment?
Biomass retention, the retention of the bacteria performing the treatment of the water, is important as without them, new bacteria would have to be added all the time. Also, a high biomass concentration will lead to high conversion rates, as there are more bacteria to perform the task, and the formation of granules enables aerobic and anaerobic environments within the same biomass, thus allowing different processes to take place simultaneously.
One traditional method for this is the sludge process, where a certain level of starvation is used to ensure that the biomass grows in flocs or granules. The center of these granules can be anaerobic (due to diffusion limitations), and it will thus allow anaerobic metabolism that is not outcompeded by the more energy-yielding aerobic processes in these anoxic environments. Also, the flocs can lead to sedimentation, allowing the biomass to remain in the system
Mention the most relevant microbial processes taking place in aerobic
granules in treatment of municipal wastewater. Why can so many different
microbial processes take place simultaneously in the granules?
The most relevant microbial processes taking place in aerobic granules during the treatment of wastewater is removal of carbon, nitrogen, and phosphorus. They take place in different parts of the granules. Due to limitations of diffusion, some parts of the granules can remain anoxic, and thus the anaerobic respiration will be able to take place without being outcompeted by microbed perforing aerobic respirations, which is more advantageous for energy production.
Glucose and organic matter is converted to the gas CO2, which leaves the water.
Ammonia, and other nitrogen-compounds can be converted to N2-gas, which will also leave the water.
Which microbial processes can be used to remove nitrogen from water? What
is the electron donor and acceptor in these processes? How can these
microbial process be selected for?
The microbial processes of denitrification and anammox (anaerobic ammonia oxidation) can remove fixed nitrogen (No2, NO3, NH4+) from water by converting the given compound into N2-gas.
In the anammox reaction, ammonium (NH4+) is oxidized to N2. oxidization is equivalent with donating electrons. NH4+ is the electron donor. It reacts with NO_2 -, which is converted into H2O, and is the electron acceptor.
In denitrification, nitrate is reduced to N2. There are multiple half-reactions, and one of the intermediates includes the gas N2O. The total reaction can still be described as 2 NO3 - + 10 e- + 12 H\ -> N2 (g) + 6 H2O.
To select for these processes, the enviroment has to be anoxic, as anerobic respiration is an advantage. Other optimalizations of environment including nutrition, pH, temperature should also be adjusted to fit the desired bacteria.
- A large, continuous industrial flow of wastewater contains only one organic
compound; a complex and slowly biodegradable organic compound, called
ContaminantA. ContaminantA is toxic and needs to be converted in a
treatment process. A research group were able to obtain a Pseudomonas
strain through genetical engineering that was able to degrade ContaminantA
at high rates. Alternatively, a ContaminantA-degrading microbiome might be
possible to obtain through selection, by serving ContaminantA as the only
available electron donor. Which of these approaches would you chose for
designing a treatment process for the wastewater? Justify your answer.
A pure monoculture is more expensive as it has to be sterilized, is at risk of contamination, and can be unpredictable in large amounts. It is also difficult to steer the functions towards the desired productions without some unforeseen complication occuring. Microbiomes, on the other hand, are cheaper and easier to select for the desired functions. Also, it is simpler.
A well-functioning human gut microbiome is highly important for human
health, whereas dysbiosis in the gut microbiome is associated with diseases.
Is it possible to steer the human gut microbiome towards a healthy
microbiome composition? Discuss reasons why this might be difficult, and
why it might work.
6:
The human gut microbiome can be affected by diet and lifestyle, and in cases of C. difficile (and probably other) takeovers, fecal transplants can introduce the desired bacteria into the gut to re-establish a good enviroment. However, it is difficult to control every aspect of the gut, like immune cells that might attack, other infectious microbes that may enter, temperature, pH, and to a certain degree nutrition. It is more difficult than say a bioreactor, where you have more total control of the enviroment.
