Daily Newsletter March 8, 2012
Daily Challenge: Bacterial Growth
You are to work with the bacterial growth equations and your understanding of bacterial growth factors to answer the following questions.
You have been hired to maximize the production of indene by Rhodococcus. Indene is a precursor used in the manufacturing of the AIDS medication Crixivan™. Given conditions of growth are 4% lactose, 3% yeast extract, oxygen saturation of 18%, and a pH of 6.8. You have ten 10ml stored cultures of the organism, with an OD that is equivalent to 105 cells/ml for this organism. Your fermentation vessel holds 15L, and is aerated and agitated to prevent the formation of biofilms (these cells need to be planktonic). The cells have a lag period of 1 hour when first introduced to a new culture from storage, and will enter late log phase when there are 108 cells/ml. From looking at a colleague’s research notes, you find that the bacterium has a generation time of 25 minutes. How long will it take to reach late log phase?
Hint: You are adding stock cultures to a 15L tank. Have you diluted these cultures? What then is your starting culture?
You have been told that you must maintain late log phase for 48 hours in order to produce a sufficient quantity of Indene. How would go about doing this?
Hint: You will need to go back to the textbook and other references to look at fermentation and continuous cultures. This is not about a "right" answer as much as it is about your thought process.
You have been asked to upscale the production to a 10,000L fermentation tank. What complications could arise when upscaling from a 100L fermentation vessel?
Hint: What problems would come up if you had more liquid or a larger volume? Give this some thought. Think about pH effects of metabolizing organisms, temperature differences in a large body of liquid, oxygenation issues.
Someone suggests that you double the lactose and yeast extract concentrations. What effects could this have on your culture (explain)? How would you go about seeing if this was a good or bad idea?
Give a brief description of Rhodococcus. What is a biofilm?
Learning objectives: What are you being asked to do in these questions? Is this about just using the growth equations? How do conditions affect bacterial growth? Is it important to be sensitive to culture environment and conditions when growing bacteria?
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