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DEMo
What’s Brewing –n- Bioreactors?
ChE 1101 Fall 2005
NASA has a number of projects with bioreactors. They are developing them to metabolize human waste (solid, liquid, and gas) on spaceships into breathable air, water, and fertilizer for plants. To read about one of these bioreactors, visit the following website: http://science.msfc.nasa.gov/newhome/br/bioreactor.htm. A new spin on cell growth All living populations go through stages of growth, which is depicted in the following graph.
Think about each stage of growth and match the phase with its definition.
EXPERIMENT: Step 1. Weigh out 0.2 grams of yeast using weighing paper on the scales and carefully pour this into your bioreactor (erlenmyer flask). Weigh out the amount of sugar your group has been assigned and add that to the bioreactor. Record these amounts on the Results Page. Step 2. Fill your bioreactor with 50°C (~120°F) water to the 75 mL line (milliliters are the same as cc’s or cubic centimeters which are also written cm3). Record this amount on your Results Page. Step 3. Stir rapidly with your stir bar until all the yeast and sugar is dissolved. Push the stopper with the bubbler in it into the bioreactor flask until it is snug. Step 4. Start your timer now. Step 5. Remove the cap from the bubbler apparatus on the top of the bioreactor. Using your squirt bottle, fill the bubbler with water up to the line marked with the arrow in the photograph above. Step 6. Place the entire bioreactor (flask and bubbler) inside the temperature bath (beaker). Fill the beaker to the 250 mL mark with warm 50°C (~120°F) water. Place the thermometer in the bath and record the temperature on your Results Page. Step 7. Your bioreactor is now together. On your Results Page, record the time of each bubble and the temperature. You may plot the results as you go on the chart provided. Results Page Step 1: Weight of sugar, Ws: Ws = __________ grams Step 2: What is the total mass entering the reactor? Step 4:
Questions: Rate of bubble production can be determined from your raw data
or from your graphs. This is the number of bubbles produced
over a period of time. Locate the 3-minute period of time
in which the number of bubbles produced was largest. Use
this to calculate the maximum bubble production your biomass
showed. What growth phase was this?_______________________________ Use the same strategy to determine the minimum bubble rate. Rmin = _____________________bubbles / sec What growth phase was this?_______________________________
What was the rate of cooling (calculate from temperature data)? Bioreactor Memo & Results (Due Nov. 3): Write up a 2 page discussion of your results, observations and conclusions. Please include plots of your data. How could a chemical engineer improve the design of these bioreactors to improve results and increase yield? |
We
are going to monitor these phases of growth in a bread yeast
population in a tiny bioreactor. From the discussion in class,
we learned that mass is conserved in every process. In
this experiment, we have 2 processes: the cellular process and
the bioreactor itself. For the cellular process,
it is necessary to understand that cells eat food and excrete
waste. Food in our system is going to be sugar, which the
cells take in and metabolize to CO2, ethanol, and hydrocarbons. We
are going to monitor CO2 production by watching how much gas
is produced from our reactor. 
