Cell membrane damage induced by lacticin 3147 enhances aldehyde formation in Lactococcus lactis IFPL730

Amino acid catabolism is mainly initiated in Lactococcus lactis by a transamination reaction that leads to the formation of alpha-keto acids. In addition, a novel alpha-keto acid decarboxylase enzyme, rare in lactic acid bacteria, responsible for the conversion of alpha-keto acids into aldehydes has been reported in L. lactis IFPL730. The effect of lacticin 3147-induced cell damage on both amino acid transamination and alpha-keto acid decarboxylation by L. lactis IFPL730 leading to the formation of aldehydes from amino acids was investigated. Cell membrane permeabilization induced by lacticin 3147 facilitated the diffusion of amino acids into the cells and thus, enhanced amino acid transamination and formation of a-keto acids. However, alpha-keto acid decarboxylation was not affected by cell membrane permeabilization since decarboxylation of alpha-keto acids in both control and lacticin 3147-treated cells were similar, suggesting that these substrates could freely diffuse inside the cells. Nevertheless, the formation of 2-methylbutyraldehyde from isoleucine was enhanced in lacticin 3147-treated cells. The increase in alpha-keto acids formation rate by L. lactis IFPL730 due to lacticin 3147-induced cell damage, led to a concomitant increase in the subsequent decarboxylation reaction that complete the metabolic pathway to aldehyde production from amino acids. The present study points out to the use of the food grade lacticin 3147 along with L. lactis IFPL730 as a valuable tool in the development of cheese flavour. (c) 2006 Elsevier B.V. All rights reserved.