Types of microorganisms

1 Problem 1 As an employee in a small biotech company you are constantly looking for new enzymes for different purposes. Your company has negotiated a contract with the Icelandic government allowing the company to take samples of microorganisms from different hot springs. You have chosen to investigate three hot springs (A, B, and C). All hot springs are aerobic but are different with respect to pH and temperature. A is 550 C and has a neutral pH. Numerous plant residues cover the bottom of the spring. B is 900 C and has a pH of 2.5. It smells strongly from sulfur, and there is no organic material present except the microorganisms in the spring. It is rich in dissolved hydrogen sulfide. C is 700 C and has a pH of 9. On the bottom of the spring lies a partially decomposed sheep carcass. 1. Which metabolic types of microorganisms (carbon source, energy source) would you expect to find in each of the three springs? 2. In which of the three springs would you look for microorganisms with active a. Lipases b. Cellulases c. Proteases 3. Which microbial processes can be responsible for the low pH in spring B? 4. In which of the three springs would you expect that the microorganisms use reverse electron transport and why? Problem 2 Fungi interact with all kinds of organisms.

The interactions can be beneficial as well as detrimental. 1. Describe briefly three different examples of beneficial interactions including how the partners in the interactions benefit from each other. 2. Describe briefly three different examples of detrimental interactions and explain the role of the fungi in each of the examples. Fungi can be used for biological control of plant pathogens. 3. Describe the different biocontrol mechanisms that fungi can use. 4. Outline a strategy for screening for a new biocontrol fungus. Problem 3 An industrial fuel ethanol plant converts corn grain into ethanol (first-generation ethanol). The starch from the grains is hydrolysed by commercial enzymes into glucose and some maltose, maltotriose and dextrins. To increase competitiveness the Board of Directors decided to implement a process able to convert corn stover into the same product (second-generation ethanol). The lignocellulosic material (corn stover) is now processed through pretreatment and enzymatic hydrolysis (also with commercial enzymes) to generate a hydrolysate mainly composed of glucose and xylose. A novel yeast strain is required for the fermentation step in the second- 2 generation ethanol process. In both processes, the sugar consumption is sequential, with glucose being consumed first. A small amount of dextrins produced in the enzymatic hydrolysis (2% of total carbohydrates) is not fermented.

1. Explain why sugar consumption is sequential in each of the fermentation processes (firstand second-generation ethanol). 2. Knowing that the ethanol yield is 90% of the theoretical maximum and that the final ethanol concentration is 6% (v/v), what is the initial sugar concentration in the secondgeneration ethanol process? 3. Yeast cells for the second-generation process are propagated in lignocellulose hydrolysate. The cells are inoculated at 0.2 g/L and are expected to have a lag phase of 2 hours and a specific growth rate of 0.3 h-1 . What is the time required to harvested the cells if 40 g/L is required for the inoculum of the fermentation step (assume no nutrient limitation to reach that cell concentration). 4. The optimal conditions for yeast propagation and ethanol production are different. Explain why and describe the optimal conditions for each process. 5. Why is a novel yeast used in the second-generation ethanol process? Name the relevant traits this organism should have to be an efficient cell factory for this process. 6. The Board of Directors decided to integrate enzyme production on-site to reduce the cost of enzymes. Which organisms could be used? Briefly describe the conditions that could be applied to produce enzymes for these first- and second-generation ethanol processes. 7. A massive contamination with bacteria is found in the enzymatic hydrolysis tank (20,000 L) of the second-generation ethanol process. This has been a common contamination and the plant operators usually use temperature to eliminate it. They know that the decimal reduction time at 80ᴼC is 2 minutes. Calculate the thermal dead rate at 80ᴼC and the thermal dead time if the contamination accounts for 106 cells/mL.