What conditions are necessary for the fermentation of sugar to produce ethanol?

Fermentation of sugar to produce ethanol primarily occurs under anaerobic conditions, meaning the process requires an absence of oxygen. This is because, in the presence of oxygen, microorganisms such as yeast would typically perform aerobic respiration, which produces carbon dioxide and water rather than ethanol. The temperature range of 25-35°C is optimal for yeast activity, enabling efficient fermentation and maximizing ethanol production.

At temperatures lower than this range, yeast activity may slow down, reducing the fermentation rate, while higher temperatures can stress the yeast cells and lead to the production of undesirable byproducts or even yeast death. Hence, the combination of anaerobic conditions and the specified temperature range is ideal for effectively fermenting sugar into ethanol.