Which one of following acids was produced by fermentation process?

Organic acids are among the most versatile ingredients in food and beverage industries. Citric acid, acetic acid, lactic acid, tartaric acid, malic acid, gluconic acid, propionic acid and fumaric acid are some of the organic acids used widely in various industries. They are obtained as the end-products or sometimes as the intermediate components of a particular biochemical cycle. Generally, organic acids are produced commercially either by chemical synthesis or fermentation. However, fermentation processes are the most commonly used method.