Question

Why couldn't yeast use both sugar and artificial sweetener for cell respiration?

Answer 1

Yeast, sugar eating fungus, use oxygen to release the energy from sugar, much like humans, in the process called "respiration". The more sugar there is, the more active the yeast will be and the faster it will grow. Yeast feeds on sucrose, fructose, glucose, and maltose, which it converts to cellular energy through alcoholic fermentation.
Sugar is more suitable for respiration.
The artificial sweeteners are less effective at promoting yeast respiration than sucrose.