2014 Bio 301 Final Exam

Student No………………………Name……………………….

40 Total Marks in 4 Sections (5 + 9 + 20 + 6)

Section 1 Algal biotechnology: (5 marks)

Answer 4 of the following 7 questions on Algal Biotechnology below:

1. What are the main macro-nutrients for the growth of microalgae? Indicate the best source of these macronutrients for large scale microalgal cultivation?

2. Explain different algal nutritional modes. If bioenergy production is the main aim of microalgal production, what would be the most efficient nutritional mode?

3. Explain the effect of photosynthetic CO2 uptake on the pH of the culture.

4. At pH 7.0 what are the main species of NH3/NH4+ present in the medium and would that be the most suitable for sustainable algal cultivation?

5. What are the main algal cultivation systems for autotrophic growth? What is the most productive cultivation system and why? Is that system the most suitable system for Western Australia?

6. What are the main light wave lengths used in photosynthesis? Can algae be grown using only these wavelengths? If so, what are the potential uses of other wavelengths?

7. Explain the concept of non-destructive hydrocarbon production from Botryococcus braunii. What are the advantages and disadvantages of this method over the conventional algae to biofuel production?

Section 2: (9 marks)

Answer all of the 3 questions (3 marks each) below:

2.1 Laboratory chemostat operation

In the laboratory class chemostats were operated for the production of the enzyme urease. Explain

· The principle of the urease enzyme essay using the probe used.

· Give an example productivity of enzyme production (give units), based on reactor volume, flow rate and enzyme activity.

· how the purity (or the level of contamination) of the culture could be estimated from the measurements that were taken.

· What would happen if the pH control failed, causing the pH to go substantially a) higher, b) lower than the desired set-point.

2.2 DiCOM process

The Perth-invented process for the microbial conversion of the organic fraction of municipal solid waste was demonstrated during the field trip at ANAECO. Answer 4 of the below 6 points

· What is the sequence and purpose of aerobic and anaerobic phases used in the process?

· What are the useful byproducts of the process?

· What is the benefit of operating more than 1 reactor?

· What was the role of CSTR-chemostats (liquid filled) operated side by side to the solid waste converting reactors?

· Why is it important to have high levels of methanogens present and how is it accomplished?

· What steps are undertaken to maximize good air supply?

2.3 Bioprocess analysis

An aerobic chemostat was operated at room temperature to degrade the substrate propanoic acid (CH3-CH2H-COOH) to CO2. The chart below shows the dissolved oxygen concentration plotted against time. At 90 seconds the air supply was stopped.

What is the current substrate degradation rate?
What is the maximum possible substrate degradation rate of this particular bioreactor based on its current oxygen supply capacity?
What is the kLa value of the chemostat?
Estimate the critical dissolved oxygen concentration of the bacteria OR their oxygen half saturation concentration (kS)

Section 3: (20 marks)

Answer 4 out of the following 5 questions. Each question carries 5 marks

3.1 Bioreactor operation

For the production of microbial cells (or products or the degradation of waste substances), continuous processing (chemostat) as well as batch processing can be used. Explain the differences of the two processes, their pros and cons with respect to productivity, contamination risk, mutations (in the case of genetically engineered organisms). Fed-Batch operation and Sequencing batch operation are further types of bioreactor operation. What is the purpose behind those?

3.2 Biological nitrogen removal

In wastewater ammonium is the key nitrogen pollutant, causing eutrophication if not removed.

· Explain the need for organic electron donors (e.g. BOD) and oxygen for successful N removal from wastewater by the process of simultaneous nitrification and denitrification (SND).

· Sketch the effect of oxygen on both nitrification and denitrification.

· Point out how one of the more recently described processes (Anammox or parallel Nitrification and Denitrification) can result in even better N removal.

3.3 Control of bioprocesses

Microbial processes need to be controlled very strictly in many cases. High cell density cultures of E. coli, simultaneous nitrification and denitrification (SND) anaerobic digestion and our laboratory chemostat were example processes requiring control. Explain for two bioprocesses:

(a) why the control is needed by pointing out the risk or likely consequences if the process was not controlled.

(b) what is measured and what is controlled.

(d) how the control loop works (setpoint, action taken when below or above)

3.4 Energetics calculations

The interspecies hydrogen transfer as it occurs during anaerobic digestion involves reactions that are close to the thermodynamic equilibrium, at which the Gibbs Free Energy change (ΔG) of a reaction is zero. The (ΔG) of a reaction can be calculated and depends on the Standard Gibbs Free Energy Change ((ΔGo) and the concentrations of products and substrates. For the interspecies hydrogen transfer between bacteria, hydrogen gas (H2) is the substrate for one species while it is the product for the other species.

(a) Sketch a plot that demonstrates how the ΔG depends on the hydrogen concentration for each reaction. Show a line that represents ΔG=zero.

(b) Explain, by referring to the plot, the effect of hydrogen concentration on the energetics of both reactions, and at which H2 concentrations the hydrogen transfer can work.

3.5 BioGeoChemical cycles

Under anaerobic conditions bacteria can carry out anaerobic respirations in which electron acceptors other than oxygen are used. a) Give examples of 2 anaerobic respirations by pointing out the electron accepting half reaction showing the electron acceptor, the number of electrons reacting and the reduced end product. b) by including also aerobic chemo-litho-trophic bacteria a cycle can be formed. Sketch such a cycle by pointing out the oxidation states of the reactants involved.

Section 4: (6 marks)

Answer 6 out of the following 8 questions. Each question carries 1 mark

4.1 Biofuel

Both, algae (e.g. Botyrococcus) and bacteria (methanogens, or ethanol producing yeasts) can be used to generate biofuels. Point out key differences between using autotrophic micro-algae or heterotrophic microorganisms approaches (“pros and cons”).

4.2 Fermentation pathways

The aerobic metabolism of sugars such as glucose by microorganisms is similar to that of plants and animals: glycolysis, TCA cycle and electron transport phosphorylation leading ultimately to the production of ATP. Explain how in the absence of oxygen anaerobic metabolism of sugar can lead to the formation of ATP.

4.3 Aerobic chemo-litho-trophic reactions

Explain what chemo-litho-trophic bacteria are and what their role is in bio-geo-chemical cycles. Give 2 examples of reactions that they catalyse.

4.4 Modelling of bioprocesses

In the simple numerical modelling approach of a batch bioprocess, we have assumed:

· a starting substrate concentration

· a rate equation (e.g. first order, or Michaelis-Menten) and

· a time interval (iteration).

How could we then predict the substrate concentration in subsequent time intervals, leading to a predicted time course of substrate degradation?

4.5 Product Yield Prediction

An industrial wastewater consisting essentially of 120 mM glycerol (CH2OH – CHOH - CH2OH) solution as the organic pollutant is considered for biological treatment. How much oxygen has to be transferred per L of wastewater for aerobic treatment? How many litres of methane gas could be produced per L of wastewater from anaerobic digestion of this effluent?

4.6 Prediction of growth

How much biomass (g/L) would you expect to be produced by a Yeast culture that degrades a glucose solution (1 mol/L) a) aerobically and b) anaerobically ?

4.7 Fermentation Pathways

Point out the principle of microbial fermentations in terms of electron flow for the ethanol or lactic fermentation and for a fermentation pathway that allows the production of more than 2 ATP/glucose.

4.8 Process monitoring and control

A proportional- integral- differential controller (PID) can be used in bioprocesses to control process parameters such as dissolved oxygen concentration or pH to a desired set-point.

· Explain how the three different elements (P, I, D) work.

· Why is an on-off controller normally not adequate?

· Why is a purely proportional controller or a purely differential controller alone not adequate?

· Give an example of a process that needs tight process control

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