Availability of Oxygen-The degree of anaerobiosis is a principal factor controlling fermentations. with yeasts. when large amounts of oxygen are present, yeast cell production is promoted.

人过研究，作为好奇而得到的产物，已开发了一批控自然过程的系统。其中之一就是过控（也包括）生物的生长来保藏食物。