dsm-firmenich, Taste, Texture & Health, Center for Food Innovation, Wageningen, 6708 WH, The Netherlands.
Wageningen University & Research, Food Microbiology, Wageningen, 6708 WG, The Netherlands.
J Appl Microbiol. 2024 Oct 3;135(10). doi: 10.1093/jambio/lxae257.
To investigate the effect of pyruvate and glucose on leucine transamination and 3-methylbutanal production by Lactococcus lactis, including the comparison with cells possessing glutamate dehydrogenase (GDH) activity.
Lactococcus lactis cells were incubated in chemically defined medium (CDM) with the pH controlled at 5.2 to mimic cheese conditions. Pyruvate supplementation stimulated the production of the key flavour compound 3-methylbutanal by 3-4 times after 72 h of incubation. Concurrently, alanine production increased, demonstrating the involvement of pyruvate in transamination reactions. Glucose-metabolizing cells excreted α-ketoisocaproic acid and produced even 3 times more 3-methylbutanal after 24 h than pyruvate-supplemented cells. Conjugal transfer technique was used to transfer the plasmid pGdh442 carrying the gdh gene encoding for GDH to L. lactis. Introducing GDH did not stimulate the excretion of α-ketoisocaproic acid and the production of 3-methylbutanal.
These results demonstrate that Lactococcus uses pyruvate to transaminate leucine into α-ketoisocaproic acid which supports 3-methylbutanal production. Surprisingly, GDH activity did not stimulate leucine transamination and 3-methylbutanal production.
研究丙酮酸和葡萄糖对乳球菌亮氨酸转氨作用和 3-甲基丁醛生成的影响，包括与具有谷氨酸脱氢酶（GDH）活性的细胞进行比较。
将乳球菌细胞在化学定义培养基（CDM）中孵育，pH 值控制在 5.2 以模拟奶酪条件。在 72 小时孵育后，丙酮酸的补充刺激了关键风味化合物 3-甲基丁醛的产生增加了 3-4 倍。同时，丙氨酸的产生增加，表明丙酮酸参与了转氨反应。葡萄糖代谢细胞分泌α-酮异己酸，并且在 24 小时后产生的 3-甲基丁醛比添加丙酮酸的细胞多 3 倍。使用共轭转移技术将携带编码 GDH 的 gdh 基因的质粒 pGdh442 转移到乳球菌中。引入 GDH 并没有刺激α-酮异己酸的排泄和 3-甲基丁醛的产生。
这些结果表明，乳球菌利用丙酮酸将亮氨酸转氨为α-酮异己酸，从而支持 3-甲基丁醛的生成。令人惊讶的是，GDH 活性并没有刺激亮氨酸转氨和 3-甲基丁醛的产生。
