Brewing much studied, the preservative nature of the soft resins is not yet fully understood, though it has been observed that unless stored at a cool temperature, the preservative nature will decrease. Brewing is the sole major commercial use of hops. Yeast is the microorganism that is responsible for fermentation in beer. Yeast metabolises the sugars extracted from grains, which produces alcohol and carbon dioxide, and thereby turns wort into beer. In addition to fermenting the beer, yeast influences the character and flavour. The dominant types of yeast used to make beer are "Saccharomyces cerevisiae", known as ale yeast, and "Saccharomyces
Low-alcohol beer commercial brewery, San Francisco's Anchor Brewing Company, also produces their "Anchor Small Beer" using the second runnings from their Old Foghorn Barleywine. The term is also used for commercially produced beers which are thought to taste too weak. The Middle East accounts for almost a third of worldwide sales of nonalcoholic and alcohol-free beer. Notable Islamic clerics in Saudi Arabia and Egypt have issued fatawa permitting the consumption of "alcohol-free" beers that can be proven to contain zero traces of alcohol. Alcohol-free beers such as Holsten, Barbican and Moussy are often available in stores and restaurants throughout the Arab world.