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In principle, any carbohydrate source containing pentoses (C₅ sugars) or hexoses (C₆ sugars) can be used for the production of lactic acid, although it is very rare that any particular microorganism is able to use all possible and available C₅ and C₆ sugars. Pure sucrose from sugarcane or sugar beets and glucose from starch are available in large amounts and readily fermentable. Polysaccharides such as cellulose or starch are more complex and need special pretreatment. When using less pure sources such as raw sugar beet juice, the impurities must be removed somewhere in the total lactic acid production process [53]. This can be done before, during, or after the fermentation. This often leads to special adaptations in the production plant. Last but not least, the local price and availability of the carbohydrate source determine the raw material of choice for industrial fermentation. Another usable disaccharide is lactose present in whey, as was used by Scheele when he discovered lactic acid in 1780 [12].