Secretion of lysine in a broth medium by lactic bacteria and yeasts associated with garri production using a synthetic gene

Abstract

Although cassava is an important food in the tropics, it has two major deficiencies which are carried over into those foods made from it: its content of toxic cyanogenic glucosides and its low content of protein and amino acids. Garri, a fermented cassava food, has previously been ameliorated using organisms which simultaneously secrete linamarase (to reduce the residual cyanide in the food), amylase (to contribute to the growth of fermenting organisms and increase the flavour) and lysine (to improve the amino-acid content of the food). Some of the organisms fermenting cassava for garri production produce appreciable quantities of linamarase and amylase, but they are low in lysine production. It was therefore decided to improve these organisms by transforming them with a synthetic lysine gene coding for an 8-lysine peptide cloned in pBluescript II SK phagemid vector under the control of lac promoter. The synthetic lysine polypeptide gene was successfully introduced into Escherichia coli DH5α and several strains of Lactobacillus spp. and Saccharomyces spp. There was a dramatic increase in lysine secretion in the organisms, ranging from about 2.5 to sixfold, following transformation with the synthetic gene.