| As the only technology currently used in vitamin C industry, the "two-step fermentation method" of 2-keto-L-gulonic acid (2KGA, a precursor of vitamin C), was established by Chinese scientists. Its distinctive feature is that the second step of the fermentation is performed by a mixture of two kinds of bacteria. In this paper, the latest research progress in the second step of fermentation in recent years is summarized. A lot of research suggested that efficiency of the fermentation depended on the number of 2KGA-producing bacterium and the activities of enzyme (L-sorbose dehydrogenase), and meanwhile 2KGA-producing bacterium′s growth and 2KGA conversion depended on "accompanying activators″, which was released by the helper bacterium. Most of research agreed that there should be a variety of accompanying activators, including proteins, amino acids, vitamins and purine. In addition, problems faced in the industrial vitamin C fermentation are also listed. The general ideas and future directions in this research field are put forward, so as to provide reference for technological progress and the sustainable development of the vitamin C industry. |
