降解多种抗生素残留的乳酸菌的筛选鉴定及特性研究

为研究和筛选高效降解抗生素残留的乳酸菌,采用高效液相色谱法与微生物学方法相结合的方式进行初步筛选,从土壤中分离获得一株乳酸菌菌株P3-4,结合菌落及菌体形态、通过Biolog自动微生物鉴定系统鉴定和16S rDNA基因序列相似性分析,鉴定菌株P3-4为乳酸片球菌（Pediococcus acidilactici）。乳酸菌P3-4在MRS培养基中具有抗生素残留降解能力,对红霉素、罗红霉素与螺旋霉素的降解率分别能达到92.1%、68.9%和82.8%。为菌株P3-4的进一步开发利用提供了理论支持。     

Phenolic compounds and the biological effects of Pu-erh teas with long-term storage

Pu-erh tea has gained more and more popularity and attracted much attention for its various biological effects. The objective of this study was to determine the active phenolic compounds and the biological effects of 15 differently aged Pu-erh teas. The results showed that 43 active phenolics, containing 7 flavan-3-ols, 11 organic acids, and esters, 3 proanthocyanidin dimers, 2 benzotropolones, and 20 flavonoid glycosides were identified based on high-performance liquid chromatography coupled to electrospray ionisation and quadrupole time-of-flight tandem mass spectrometry (HPLC-ESI-QTOF-MS/MS). In particular, 2’-O-galloylhyperin and quercetin-3-O-p-coumaroyl-rhamnosyl-arabinosyl-hexoside were identified from constituents of tea for the first time. The 15 Pu-erh teas exhibited strong DPPH and ABTS scavenging activity in a concentration-dependent manner with IC₅₀ 0.99–2.12 and 0.97–2.67 mmol Trolox equivalent antioxidant capacity/g, respectively. All of the Pu-erh teas tested significantly inhibited the proliferation of SMMC-7721 cells, in a dosage-dependent manner. Of the 15 Pu-erh teas examined, the cake tea P6 had the strongest effect on SMMC-7721 cells with IC₅₀ = 65.88 ± 3.53 µg/mL. The others Pu-erh teas had an IC₅₀ = 96 – 509 µg/mL. Our results also indicated that not all the older Pu-erh teas display stronger anti-activities and anti-cancer than the younger ones and the youngest Pu-erh tea did not possess the highest level of active components. This study provides useful information for consumers to deeply understand the chemical constituents and bioactivity of Pu-erh tea preserved for a long time.     

Characterization of Metabolic Pathways and Absorption of Sea Cucumber Saponins,Holothurin A and Echinoside A,in Vitro and in Vivo

Sea cucumber saponins (SCSs) exhibit a wide spectrum of bioactivities, but their metabolic characteristics are not well elucidated. In this study, the metabolism of holothurin A (HA) and echinoside A (EA), 2 major saponins in sea cucumber, by gut microflora were investigated. First, we conducted an in vitro study, where in the SCSs were incubated with intestinal microflora and the metabolites were detected by high pressure liquid chromatography–high resolution mass spectrometry. We also conducted an in vivo study on rats, where in the intestinal contents, serum, urine, and feces were collected and evaluated after oral administration of SCSs. In the in vitro study, we identified 6 deglycosylated metabolites of HA and EA, assigned M1‐M6. In the in vivo study, we found all the deglycosylated metabolites in the intestinal contents after oral administration, and both the metabolites and their prototype components could be absorbed. Four metabolites were identified in the serum, 6 in the urine, and 4 in the feces. The saponins with different structures showed different absorption characteristics in rats. According to our results, deglycosylation is the main intestinal microflora‐mediated metabolic pathway for SCSs, and both the SCSs and deglycosylated metabolites can be absorbed by intestine. This study improves the understanding of the metabolism of HA and EA by gut flora, which will be useful for further analysis of the bioactivity mechanism of SCSs.