Production of Organic Acids by Solid-state Fermentation

Abstract

The global market for fermentation products was estimated as $14.1 billion in 2004 and was expected to rise at an average annual growth rate (AAGR) of 4.7% to $17.8 billion in 2009. In this context, organic acids represent the third largest category among the other products. Total market value of organic acid is expected to rise to $3 million in 2009 (Marz 2005). Organic acids are among the most versatile ingredients in food and beverage industries. Citric acid, acetic acid, lactic acid, tartaric acid, malic acid, gluconic acid, propionic acid and fumaric acid are some of the organic acids used widely in various industries. They are obtained as the end-products or sometimes as the intermediate components of a particular biochemical cycle. Generally, organic acids are produced commercially either by chemical synthesis or fermentation. However, fermentation processes are the most commonly used method. All organic acids of tricarboxylic acid cycle can be produced in high yields in microbiological processes. Among fermentation processes, the production of organic acids is dominated by submerged fermentation. Table 1 presents some facts about global production of organic acids. Global production of citric acid has reached 1.4 million tons with annual growths of 3.5-4.0% in demand/consumption rate of citric acid. In terms of volume, citric acid and acetic acid together account for about three-quarters of food acidulants.