How is DL-malic acid produced?

DL-malic acid, also known as malate, is a dicarboxylic acid commonly found in many fruits and vegetables. It is produced industrially through various methods, including chemical synthesis and fermentation processes. One of the most common methods for producing DL-malic acid is through microbial fermentation. Here's a simplified overview of the fermentation process:

Microbial Selection: 

Certain microorganisms, such as bacteria and fungi, are capable of fermenting sugars into malic acid. Among them, strains of bacteria from the genus Aspergillus and Bacillus are commonly used.

Medium Preparation: 

A suitable medium containing a carbon source (such as glucose or sucrose), nitrogen source, minerals, and other nutrients is prepared. The composition of the medium can influence the yield and productivity of malic acid.


The selected microorganism is inoculated into the prepared medium under sterile conditions. The inoculum may be obtained from a pure culture of the desired strain.


The fermentation process is carried out under controlled conditions of temperature, pH, agitation, and aeration. These conditions optimize the growth and metabolic activity of the microorganisms, leading to the conversion of sugars into malic acid.

Product Recovery: 

Once the fermentation is complete and the desired concentration of malic acid is achieved, the broth is processed to recover the malic acid. This typically involves separation techniques such as filtration, centrifugation, and/or purification through methods like crystallization or chromatography.

DL-Malic Acid Formation: 

It's important to note that DL-malic acid is a racemic mixture of L-malic acid and D-malic acid. During fermentation, both enantiomers are produced. Separation techniques may be employed if specifically only one enantiomer is desired.

Purification and Refining: 

The recovered malic acid may undergo further purification and refining steps to meet specific quality standards and remove impurities.

Overall, microbial fermentation offers a sustainable and cost-effective method for producing DL-malic acid on an industrial scale. However, it's essential to optimize the fermentation process and strain selection to maximize yields and minimize production costs.