Case scenario A waste product for cheese making is whey. You have been tasked wi

Question

Case scenario

A waste product for cheese making is whey. You have been tasked with finding a use for the whey from Swiss cheese (aside from a dietary supplement for humans). You isolate a microbe that is genetically related to Lactobacillus. This microbe is able to grow exceptionally well on the whey when you allow for aeration of the culture – it grows weakly without aeration and the pH drops dramatically over time due to an acidic waste product. See Figure 1 and Table 1 for the structure of lactose and the composition of whey. When you sequence the genome you identify genes for Embden Meyerhoff Parnas as well as oxidoreductases and quinones. You also notice it produces an interesting antibiotic when grown in a closed batch system.

7. To grow the microorganism, what type of carbon and energy would you provide along with oxygen conditions? Include clues from the case study to explain your answer.

Table 1. Composition of milk, cheese whev and casein whev % by weight Fat Lactose (milk sugar) Casein protein Whey protein Minerals Minor components Water TOTAL Milk 4.7 4.5 2.7 0.55 0.85 0.20 86.5 100.00 Cheese whey 0.05 5.0 0.10 0.65 0.50 0.30 93.4 100.00

Explanation / Answer

As per the details, the microbe is using lactose for deriving energy through aerobic respiration. However, lactose is broken down to galactose and glucose before both these simple sugars enter glycolysis independently.

So, I would provide glucose or lactose as carbon source in addition to aeration. Aerobic cellular respiration itself yields energy in the form of ATPs. So, this does not require energy unlike photosynthesis.

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