The conversion of ethanol to lactic acid can occur through a biological process known as fermentation. This process involves the action of certain microorganisms, specifically lactic acid bacteria (LAB), which can metabolize ethanol and produce lactic acid as a byproduct. The conversion steps can be summarized as follows:
Fermentation initiation: LAB, such as Lactobacillus and Streptococcus species, are commonly used for this conversion. They are added to a suitable medium containing ethanol, which serves as the substrate for fermentation.
Glycolysis: The LAB utilize a series of enzymatic reactions to break down the ethanol via glycolysis. In this process, the ethanol is converted to acetaldehyde by the enzyme alcohol dehydrogenase.
Conversion to lactic acid: The acetaldehyde produced from the previous step is then further metabolized to lactic acid by the enzyme lactate dehydrogenase. This conversion involves the transfer of electrons from NADH (nicotinamide adenine dinucleotide) to acetaldehyde, resulting in the formation of NAD+ and lactic acid.
Overall, the reaction can be summarized as:
Ethanol + NAD+ → Acetaldehyde + NADH + H+ Acetaldehyde + NADH + H+ → Lactic acid + NAD+
The lactic acid produced can be used for various purposes, including food and beverage production (e.g., in yogurt, cheese, and sourdough bread) and industrial applications (e.g., bioplastics and pharmaceuticals).
It's worth noting that this biological conversion is different from the chemical conversion of ethanol to lactic acid, which typically involves complex and controlled reactions under specific conditions using catalysts and reagents.