Impact of kdcA, pdhD, and codY gene regulation in Lactococcus lactis 408 on 3-methylbutanal formation during cheddar cheese ripening.

3-Methylbutanal, a key volatile compound contributing to the nutty flavor of cheese, was primarily produced through the microbial catabolism of leucine. This study focused on the metabolic pathway of 3-methylbutanal at the genetic level during the ripening of Cheddar cheese. The influence of key genes (kdcA, pdhD, and codY) in Lactococcus lactis 408, a specifically selected adjunct culture, on the production of 3-methylbutanal was evaluated. Over a 14-day ripening period, a minor difference in leucine production was observed among different samples with adjunct culture, while alterations in the genes kdcA and pdhD, which were overexpressed in the strain, led to a decreased concentration of α-ketoisocaproate. Utilizing headspace solid-phase microextraction coupled with gas chromatography-flame ionization detection, a reduction was observed in 3-methylbutanal levels as ripening progressed. However, cheese fermented with the codY knockout strain displayed the highest level of 3-methylbutanal at both 0.5-day and 28-day ripening milestones. Further analysis using an Ag/AgCl electrode to assess the redox environment revealed that the higher redox potential in the codY knockout strain was instrumental in retaining elevated levels of 3-methylbutanal. These findings underscored the critical role of genetic factors in the flavor development of cheese and offered promising targets for enhancing flavor profiles in dairy products through biotechnological interventions.