A preliminary study on the effect of Lactobacillus casei expressing cystathionine lyase1/cystathionine lyase2 on Cheddar cheese and the formation of sulphur-containing compounds

Model Cheddar cheeses were manufactured from pasteurised milk with various Lactobacillus casei adjuncts. The added L. casei FAM18101, L. casei FAM18108, and L. casei FAM18149 possessed genetic variants of a gene cluster that is involved in the conversion of methionine to cysteine. The gene cluster comprises a cystathionine lyase (ctl) previously shown to degrade cysteine, homocysteine, cystathionine and methionine to volatile sulphur compounds such as hydrogen sulphide and methanethiol. A strain that does not possess the gene cluster was used as a control. An inhibitory effect of the adjuncts on starter culture activity was not observed. Expression analysis of the genetic variant ctl1 showed that the gene was expressed in cheese. The development of cysteine, methionine and volatile sulphur compounds was analysed during ripening. The cheeses containing the L. casei adjuncts possessing the gene cluster had markedly higher concentrations of cysteine, hydrogen sulphide and methanethiol at the end of ripening.