Enhancing the biosynthesis of nicotinamide mononucleotide in Lactococcus lactis by heterologous expression of FtnadE.

BACKGROUND: Nicotinamide mononucleotide (NMN), a key intermediate of nicotinamide adenine dinucleotide, plays an important in anti-aging and disease. Lactococcus lactis, an important probiotic lactic acid bacteria (LAB), has shown great potential for the biosynthesis of NMN, which will significantly affect the probiotic effects of the dairy products. RESULTS: We used the CRISPR/nCas9 technique to knockout nadR gene of L. lactis NZ9000 to enhance the accumulation of NMN by 61%. The nadE* gene from Francisella tularensis with codon optimization was heterologous in L. lactis NZ9000ΔnadR and has a positive effect on NMN production. Combined with optimization of the concentration of substrate nicotinamide, a final intracellular NMN titer was 2289 µmol L-1  mg-1 with 10 g L-1 nicotinamide supplement, which was 5.7-fold higher than that of the control. The transcription levels of key genes (pncA, nadD and prs1) involved in NMN biosynthesis were up-regulated by more than two-fold, indicating that the increase of NMN titer was attributed to FtnadE* heterologous expression. CONCLUSION: Our study provides a better understanding of the NMN biosynthesis pathway in L. lactis, and can facilitate NMN production in LAB via synthetic biology approaches. © 2022 Society of Chemical Industry.

Antimicrobial and cytotoxic juglones from the immature exocarps of Juglans mandshurica.

Juglonols A-C (1-3), three new juglone derivatives possessing a hydroxyethyl side chain, were isolated from an organic extract of the immature exocarps of Juglans mandshurica together with five known tetralones (4-8). Their structures were elucidated by extensive spectroscopic analyses and comparison with literature data. The new juglone derivatives exhibited inhibitory activities towards a panel of bacteria and fungi, as well as cancer cell lines. In contrast, the known tetralone homologues (4-8) appeared to be much less efficacy.

PPAR-γ and tollip are associated with toll-like receptors in colitis rats.

To elucidate the significance of Toll-like receptors and their negative regulating factors PPAR-γ and Tollip on the pathogenesis of colitis. Colitis model was induced by TNBS in rat. The expression of TLR2, TLR4, NF-κBp65, PPAR-γ and Tollip was examined by immunohistochemistry (IHC) and reverse-transcription polymerase chain reaction (RT-PCR). RT-PCR revealed a significant increased expression of TLR2, TLR4, and NF-κBp65 in the colitis group compared with the normal group (TLR2: 1.057 ± 0.092, 0.463 ± 0.101, t = 4.125, P = 0.001; TLR4: 0.376 ± 0.029, 0.215 ± 0.049, t = 2.731, P = 0.013; NF-κBp65: 0.746 ± 0.049, 0.206 ± 0.063, t = 6.055, P = 0.000). The expression was positively correlated with the generally damage score and the histological injury score correspondingly (TLR2: r = 0.573, r = 0.559; TLR4: r = 0.754, r = 0.866; NF-κBp65: r = 0.548, r = 0.919). The Tollip mRNA wasn't obviously diversity between the normal and colitis groups by RT-PCR (Tollip: 0.288 ± 0.050, 0.140 ± 0.046, t = 1.993, P = 0.061). While the Tollip protein was mainly assembled in the lamina propriaand higher in the colitis group compared with the normal group by IHC. The expression of PPAR-γ in the colitis group was obviously lower than that in the normal group (PPAR-γ: 0.255 ± 0.065, 0.568 ± 0.072, t = 2.882, P = 0.010). The expression of Tollip and PPAR-γ was negative correlated with the generally damage score and histological injury score correspondingly (Tollip: r = -0.497, r = -0.551; PPAR-γ: r = -0.683, r = -0.853). The disbalance between TLRs and their negative regulating factors PPAR-γ and Tollip was closely associated with the course of colitis.