Discussion #6- Fermented Food (and drink) World Tour

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Cells must have ATP to survive. ATP is the form of energy that cells can use to do work. Cells get ATP through the breakdown of food (breaking bonds in the food molecules), mainly glucose. It does not matter if the cell made the glucose itself (autotrophy, like in photosynthesis) or if the cell had to ‘eat’ to get that glucose (heterotrophy, like what happens in you- you either eat the plants that made the glucose, or eat something that ate the plants, like beef from cattle).  So, yes, plants also undergo cellular respiration. 

There are two major ways to break down glucose (food) and convert the energy in the bonds to an ATP form that cells can use: 

1)Those that require oxygen: Aerobic Cellular Respiration

 

This happens in 3 main stages (see 6.2-6.5 in your text for details). In this form, oxygen is required to completely breakdown a molecule of glucose- converting the bond energy to ATP, which the cell is able to use.  The CO2 is a gaseous waste product (which you exhale) and the remaining atoms are rearranged to form H20, which is either used by cells or, any excess is released as a waste product (urine, sweat). Cells need to continually have food to convert to ATP to do work- physical work like heart cell contraction, or electrical work in nerve cells, and active transport in lots of cells. Because the glucose is completely broken down, it results in lots of ATP (on average, 36 molecules per glucose molecule).

2) Those that do not require oxygen (two main types)

a. anaerobic cellular respiration-similar to aerobic, but rather than use oxygen, these microbes (bacteria, archaea) use nitrate, sulfates, etc. They produce a ‘medium’ level of ATP per molecule of glucose. 

b. fermentation- in this process, cells only produce the ATP from glycolysis (the same glycolysis from step 1 in aerobic respiration). Fermentation regenerates the ‘ingredients’ needed for glycolysis. This only partially breaks down glucose, so the ATP yield is very low. This method can be performed by many types of cells: bacteria, yeast, and even human cells in low oxygen conditions. 

Alcoholic fermentation results in the production of ethanol, an alcohol. Glucose is broken down to ethanol (2, 2-carbon molecules) and 2 CO2 molecules which are released as a gas. The source of the glucose helps to determine the flavor of the ethanol- fermenting the sugar in grapes results in wine, different grapes = different taste. 

Lactic Acid fermentation breaks the glucose in half which releases some ATP energy. The remaining molecules are rearranged to lactic acid molecules (a 3-carbon molecule), which gives a somewhat sour taste. The taste varies by what source of glucose the fermenting cell is using.  For example, lactose sugar in milk being fermented produces a different taste than the fermentation of vegetable/fruit/animal sugars.

Remember, pyruvate is  3-carbon molecule  that results from the splitting of the 6-carbon glucose in glycolysis. So one glucose, splits into two pyruvates.

FOR THIS WEEK….

I just looked in my pantry/fridge and quickly recognized the following: ginger ale, coffee, chocolate, sour cream, soy sauce. All food products made from fermentation in some way.  We are going to take a little different approach to the Discussion this week…Below is a list of food/drink from around the world and the likely location of origin. They are all produced with the help of fermentation- either lactic acid or alcoholic. The list is first come first serve—each item can only be selected once–make sure to review what has been posted by your classmates and select an item that has not yet been presented. You will choose one (or see below for other options), do some research and post the following:

• Tell us about how this food/drink is the product of fermentation: which type of fermentation: lactic acid vs. ethanol fermentation? What is the source of the sugar? What microorganisms are doing the fermenting? What happens to the CO2 produced if it is alcoholic? Other info as appropriate. Describe and explain…provide more than one word answers here- for example, don’t just say, “Yeasts alcoholically ferments grapes to make wine”. Tell us about the process as it is specific to wine–grape juice it not alcoholic, so how does it go from ‘must’ (unfermented juice) to wine?
• Include at least one photo (either the finished product, the sugar source, the major microorganisms doing the fermenting, the process, etc.). Feel free to include more than one, please make sure to tell us what we are seeing. Make sure to put figures in the post vs. as an attachment- this way they can easily be seen.
• Tell us something about the importance/use/history of the food item. Include if you have tasted it/like it/hate it/made it, etc. 
• Tell us the COOLEST/GROSSEST/MOST INTERESTING thing you learned about this product and why you found that interesting.
• Don’t forget complete citations for sources for your research and your  images.

Fermented Products:

• miso (Japan)
• sauerkraut (Europe)
• kombucha (some sources say Russia/Ukraine, others say China)
• sake (Japan)
• gin (Europe, Netherlands?)
• vodka (Russia)
• scotch/scotch whisky (Scotland)
• tempeh (Indonesia)
• poi (Polynesia/Hawaii)
• yogurt (Central Asia)
• kimchi (Korea)
• bourbon (USA, Kentucky)
• tequila (Mexico)
• rum (West Indies, possibly Barbados?)
• hard cider (Great Britain)
• injera (Ethiopia)
• hakarl (Iceland)
• kiviak (Greenland/Inuits)
• natto (Japan)
• Swiss cheese (Switzerland)
• sourdough bread (Europe/USA…but the best sourdough culture comes from my kitchen! 😉 )
• puto (Philippines)
• fermented giardiniera (Italy- not ‘pickled’ but traditionally fermented)
• stinky tofu (China/Taiwan) side note- this REALLY lives up to its name! 
• garri (West Africa- I had it quite often in Senegal). 
• Tabasco brand hot sauce (USA)
• Worcestershire sauce (England)

If you are familiar with another fermented food not on this list, please let us know! We have a diversity of students in this class (in terms of ethnicity, country of origin, travel experiences, etc.)- it would be awesome to hear about the fermented food in additional cultures!