To develop any chemical or biochemical technology for recycling carbon dioxide to serve as a counter-measure against carbon dioxide elevation in the at­mosphere, it is obvious that the process should not use fossil fuel. In this regard, it is also better to avoid aerobic bioprocesses which are accompanied by carbon di­oxide emission. Aerobic bioprocesses involve the oxidation of organic substrates by oxygen and this is the same principle of fossil fuel combustion. It is therefore preferable that anaerobic bioprocess should be adapted for bioconversion which allows less carbon dioxide emission. Some anaerobic reactions do not involve the production of carbon dioxide, some result in small quantities being produced, but others produce comparatively large amounts during the entire course of the fer­mentation. For example, fermentation involving the metabolic pathway in which pyrvate is converted into acetyl-CoA, with the release of carbon dioxide, inher­ently produce one mole of carbon dioxide for each mole of substrate consumed. Hence, anaerobic fermentation yielding ethanol, butanol, acetone, acetoin, and butanediol are accompanied by the production of carbon dioxide, while lactate formation from pyrvate is not accompanied by the release of carbon dioxide. Thus, lactate fermentation has advantages over other anaerobic fermentation such as ethanol fermentation from the point of view of carbon dioxide release during the biochemical reaction.

In general, anaerobic fermentation has advantages as 1. energy gaining metabolism, 2. less carbon dioxide, 3. accompanying metabolites as electron ac­ceptor, while, it has disadvantages as 1. low cell density, 2. product inhibition, and 3. complex nutrition requirement. These disadvantages are sometimes bottle­neck to attain efficient fermentation.