Back in your office you have a jet leg, a little head ache and already in the plane you realized that your margins for success are small to reach the 15 M€/yr profit target.

Yield on substrate is 0.51 or lower, making the substrate part in the cost already 0.6 €/kg or higher. It is not allowed to be much higher, because then your (relative) margin will be too low to ever reach that 15 M€/yr.

On the other hand you have to produce a lot of ethanol, so the total amount you produce is also relevant. For instance minimizing costs due to glucose per kg of ethanol will surely lead you to the conclusion that near to maintenance conditions is the best option; however then the volumetric productivity and total amount of ethanol produced might be too low.

Your first task is clear: Analyze the ethanol fermentation and determine optimal fermentation conditions to reach the 15 M€/yr profit target.

First step is to compose the stoichiometric equations and determine rates. Then these can be used to make calculations for costs and profit. You start with the simple one, the catabolic one.

**Compose the catabolic stoichiometry equation from this
list of molecules and numbers:**

_{2}H

_{6}O

_{6}H

_{12}O

_{6}

_{2}O

_{4}O

_{1.8}O

_{0.5}N

_{0.2}

_{2}

^{+}

_{2}O

_{4}

^{+}

_{2}