Die Produksie van L-Malaat Deur Mikro Organismes

Abstract

L-Malic acid is of great importance as a food and beverage acidulant and is also used in the treatment of metabolic disorders such as hyperammonemia and liver disfunction. This acid from the citric acid cycle is an essential intermediate of cell metabolism and is one of the major acids in apples, other fruits and plants. The trend to use more natural food ingredients may increase the demand for L-malic acid. The chemical and enzymatic production of the L-isomer of malic acid is expensive and time consuming and because this acid is not manufactured in South Africa, it needs to be imported at a very high cost. We therefore investigated the potential of the microbiological production of L-malic acid. A large number of acid forming bacteria were selected for fumarase activity on a selective medium containing fumarate as the only carbon source. Of the three organisms with high fumarase activity, only one organism produced substantial amounts of L-malic acid and was selected for further study. The identity of the isomer (which has to be the L-isomer) formed by this bacterium was confirmed by GC analysis after derivitization with R-(- )-2-butanol. This result was confirmed with a L-isomer-specific enzymatic assay. A paperchromatographic method was developed to analyse a large number of samples. In this way the growth conditions (pH, temperature, time and concentration) for optimum L-malic acid production were determined. These conditions were verified with a more quantitative test.