During the 19th century, several of the fundamental concepts of organic chemistry were discovered. Joseph Louis Gay-Lussac was interested in fermentation processes. One of his students was Justus von Liebig. Both independently described the chemical structure of the lactic acid molecule. Both were chemists, they were only interested in the chemical properties, and how to optimize it using chemical catalyzers. The French chemist Louis Pasteur was the first to describe lactic acid as a product of a microbial fermentation, in 1857. At the time he worked at the University of Lille. A local brewery asked him about some problems they had with fermentation. By chance he discovered that in this brewery, two fermentation processes were taking place: One was the lactic acid fermentation he had expected, the other was an alcoholic fermentation. Both were started by microorganisms.