L-Theanine is a health-beneficial tea-specific amino acid. This amino acid is synthesized through the catalytic action of L-theanine synthase or its isoenzymes, utilizing ethylamine and L-glutamic acid as primary substrates. As the rate-limiting substance, traditional ethylamine synthesis relies on tea root metabolism, and exploring new synthetic pathways can boost L-theanine production and explore environmental application values. Self-developed Tongji_Software was used to predict a potential pathway for ethylamine synthesis. A cell-free protein synthesis (CFPS) system was adopted for verification, and genome engineering was performed to construct a recombinant strain. According to the software predictions, atrazine chlorohydrolase (AtzA) and hydroxyatrazine deethylaminase (AtzB) could convert the herbicide atrazine into ethylamine. CFPS based on Pseudomonas knackmussii (P. knackmussii) produced 88.5 μM L-theanine within a 24-h period, while the engineered strain P. knackmussii-AtzAB yielded 445.7 μM with the conversion rate of 44.6% over 84 h of fermentation. In summary, we revealed a novel pathway for ethylamine synthesis, which can promote L-theanine accumulation in tea trees and degrade environmental pollutants.
S. Yu, J. Feng, G. Zhou et al.· Plant biology· 0 citations
Previous studies have demonstrated that Bifidobacterium lactis (B. lactis) XLTG11 exerts significant immunomodulatory effects. However, the underlying mechanisms remain unclear. To investigate these mechanisms, BALB/c mice were randomly divided into three groups: normal control (NC), model control (MC), and B. lactis XLTG11 (XL) groups. We assessed spleen and thymus indices, jejunal histopathology, leukocyte and IgA cell counts, as well as the levels of interferon (IFN)-γ, interleukin (IL)-2, IL-4, IL-12, and secretory IgA (SIgA) in the small intestine. We also analysed the composition and diversity of the gut microbiota. The results showed that B. lactis XLTG11 restored villus height and crypt depth, thereby alleviating jejunal tissue damage. Furthermore, B. lactis XLTG11 treatment significantly increased the counts of leukocytes, goblet cells, and IgA cells, and elevated the levels of the aforementioned cytokines and SIgA. It also increased thymus indices without affecting spleen indices. Regarding the gut microbiota, B. lactis XLTG11 reduced the Bacillota/Bacteroidota ratio and modulated microbial composition and diversity. Spearman's correlation analysis revealed significant associations between specific microbial taxa and the immune parameters measured above. Collectively, these findings demonstrate that B. lactis XLTG11 can modulate immune function, and the underlying mechanisms involve repairing the intestinal mucosal barrier, regulating the levels of immune cells and cytokines, and maintaining gut microbiota homeostasis.
S. Zhang, L. Lian, H. Yu et al.· Beneficial Microbes· 0 citations
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