College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, China.
Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou University, Yangzhou 225127, China.
J Ind Microbiol Biotechnol. 2022 Oct 13;49(5). doi: 10.1093/jimb/kuac020.
It has been found that 32 genes related to nitrogen source metabolism in Lacticaseibacillus rhamnosus are downregulated under both heat stress and oxidative stress. In this study, the influence of different nitrogen sources within the growth medium on the tolerance of L. rhamnosus to heat stress and oxidative stress was investigated. Tryptone-free MRS was found to enhance the tolerance of L. rhamnosus hsryfm 1301 to heat stress and oxidative stress during the whole growth period, and this result was universal for all L. rhamnosus species analyzed. The strongest strengthening effect occurred when the OD600 value reached 2.0, at which the survival rates under heat stress and oxidative stress increased 130-fold and 40-fold, respectively. After supplementing phenylalanine, isoleucine, glutamate, valine, histidine, or tryptophan into the tryptone-free MRS, the tolerance of L. rhamnosus to heat stress and oxidative stress exhibited a sharp drop. The spray drying survival rate of L. rhamnosus hsryfm 1301 cultured in the tryptone-free MRS rose to 75% (from 30%), and the spray dried powder also performed better in the experimentally simulated gastrointestinal digestion. These results showed that decreasing the intake of amino acids is an important mechanism for L. rhamnosus to tolerate heat stress and oxidative stress. When L. rhamnosus is cultured for spray drying, the concentration of the nitrogen source's components should be an important consideration.
已发现，在干酪乳杆菌中，与氮源代谢相关的 32 个基因在热应激和氧化应激下均下调。在本研究中，研究了生长培养基中不同氮源对干酪乳杆菌耐热应激和氧化应激能力的影响。研究发现，无蛋白胨 MRS 可增强干酪乳杆菌 hsryfm 1301 在整个生长周期中的耐热应激和抗氧化应激能力，这一结果适用于所有分析的干酪乳杆菌属物种。当 OD600 值达到 2.0 时，强化效果最强，此时耐热应激和氧化应激下的存活率分别增加了 130 倍和 40 倍。在无蛋白胨 MRS 中补充苯丙氨酸、异亮氨酸、谷氨酸、缬氨酸、组氨酸或色氨酸后，干酪乳杆菌对热应激和氧化应激的耐受性急剧下降。在无蛋白胨 MRS 中培养的干酪乳杆菌 hsryfm 1301 的喷雾干燥存活率上升至 75%（从 30%），喷雾干燥后的粉末在实验模拟的胃肠道消化中也表现更好。这些结果表明，减少氨基酸的摄入是干酪乳杆菌耐受热应激和氧化应激的重要机制。当干酪乳杆菌用于喷雾干燥培养时，氮源成分的浓度应是一个重要的考虑因素。
