What product has wheat flour as its substrate and yeast as the microbe? *

Wheat flour contains starch. The starch is hydrolysed to glucose. Glucose is used by yeast(saccharomyces cerevisae) to make ethanol.

C6H12O6(glucose from wheat flour)---(yeast)-->2C2H5O(ethanol)+2CO2

Ethanol is the main product

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.