Introduction

The story of amino acid production started in Japan in 1908 when the chemist, Dr K. Ikeda, was working on the flavouring components of kelp. The specific taste of the kelp preparations, kombu and katsuobushi, is traditionally very popular with the Japanese (Fig. 14.1). After acid hydrolysis and fractionation of kelp, Dr Ikeda discovered that one specific fraction he had isolated consisted of glutamic acid which, after neutralization with caustic soda, developed an entirely new delicious taste. This was the birth of the use of monosodium glutamate as a flavour-enhancing compound. The production of monosodium glutamate (MSG) was soon commercialised by the Ajinomoto Co. Ltd based on its isolation from vegetable proteins such as soy or wheat protein. However, with this process the waste fraction was high, and also the chemical synthesis of d,l-glutamate was of little use since the sodium salt of the d-isomer is tasteless.

The breakthrough in the production of MSG was the isolation of a specific bacterium by Dr S. Udaka and Dr S. Kinoshita at Kyowa Hakko Kogyo in 1957. They screened for amino-acid-excreting microorganisms and discovered that their isolate, No. 534, on a mineral salt medium excreted l-glutamate. It soon became apparent that the isolated organism needed biotin and that l-glutamate excretion was triggered by an insufficient biotin supply. A number of bacteria with similar properties were also isolated, which are today all known by the species name Corynebacterium glutamicum (Fig. 14.2). Corynebacterium glutamicum is a Gram-positive bacterium which can be isolated from soil.