Citric Acid Production of Yeasts: An Overview

Background Citric acid, an intermediate product of the Krebs cycle, has a wide usage area in the food industry since it has some functions such as acidulant, flavouring agent, preservative and antioxidant. Although molds are the most commonly used microorganisms in the citric acid production, it is known that there are significant advantages of using yeasts. Purpose and scope The microbial citric acid production mechanism needs to be well understood to make production more efficient. In this study, the yeasts used in the production, fermentation types and the factors affecting production were reviewed with studies. Methodology Although production of citric acid can be produced by chemical synthesis, the fermentation is preferred because of its low cost and ease of use. More than 90% of citric acid produced in the world is obtained by fermentation. Results Yarrowia lipolytica, Candida zeylanoides and Candida oleophila are evaluated for citric acid production with substrates such as molasses, glucose, sucrose and glycerol. On the other hand, there is great interest in developing processes with new substrates and/ or microorganisms. Conclusion Although the microbial strain is an important factor, the factors such as carbon, phosphorus and nitrogen sources, aeration, the presence of trace elements and pH are also parameters affecting the production.