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Background Probiotics are defined as microorganisms that can exert health benefits for the host. Among the recognized probiotics, Lactobacillus paracasei are one of the most frequently used probiotics in humans. The L. paracasei strain M11-4, isolated from fermented rice, which could ferment soymilk within a short curd time, and fermented soymilk presented high viability, acceptable flavor and antioxidant activity, which revealed that the strain maybe have a potential antioxidant value. Therefore, it is necessary to further explore the antioxidant activity of L. paracasei strain M11-4. Results The radical scavenging activities, lipid peroxidation inhibition, and reducing power of L. paracasei M11-4 were the highest in the fermentation culture without cells, while the activities of other antioxidant enzymes of L. paracasei M11-4 were high in the cell-free extract and bacterial suspension. Moreover, L. paracasei M11-4 exerted its antioxidant effect by upregulating the gene expression of its antioxidant enzymes, thioredoxin (Trx) and glutathione (GSH) systems when hydrogen peroxide (H2 O2 ) existed. Supplementation of rats with L. paracasei M11-4 effectively alleviated D-galactose-induced oxidative damage in the liver and serum and prevented D-galactose-induced changes to intestinal microbiota. Supplementation with L. paracasei M11-4 also reduced the elevated expression of Trx and GSH system genes induced by D-galactose. Conclusion L. paracasei M11-4 has good antioxidant properties both in vitro and in vivo and the antioxidant mechanism of it was studied at the molecular level. This article is protected by copyright. All rights reserved.

This study investigated the effects of a Lactobacillus paracasei KL1 and Lactobacillus plantarum subsp. plantarum Zhang-LL mixed probiotic on Salmonella-caused pullorosis in chicks. A total of 120 1-day-old Nongda no.3 dwarf chicks were randomly assigned to 4 treatments, with 6 replicates of 5 birds each. The treatments were blank group, Salmonella pullorum–infected group, probiotic treatment group, and probiotic prevention (PP) group. All birds (n = 90) except those in the blank group were infected with S. pullorum on day 4. On day 14, the BW, ADG, mortality, pathology of tissue, cecum colony count, immune organ indices, cecal mucosa secretory IgA, and cytokines were investigated. The results showed that the chicks infected with S. pullorum were depressed and their BW reduced. The PP group had the highest ADG and lowest mortality rate (0%), whereas the S. pullorum–infected group had 37.50% mortality rate and lowest ADG. Pathologic sections showed that the probiotic treatment group had minor lesions but the PP group had no lesions in the ileum, cecum, and liver. Cecal Lactobacillus counts was the highest (P 0.05) in the bursa of Fabricius, whereas in the PP group, all the immune organs were increased (P

The quorum-sensing regulation of class II bacteriocin (AcH) synthesis in Lactobacillus plantarum subsp. plantarum Zhang-LL was studied. No detectable inhibition zone was formed by the supernatant of L. plantarum subsp. plantarum Zhang-LL culture in skim milk (SM) with an inoculum size of 7 × 102 CFU/mL after incubation for 36 h. Hence, this culture system was used to investigate the induced regulation mechanism of bacteriocin production in L. plantarum subsp. plantarum Zhang-LL. Bacteriocin production by this bacterium in SM medium was induced by treatment with inactivated culture supernatant from de Man Rogosa Sharpe (MRS) medium (supernatant-MRS). Pediocin AcH encoded by the papA gene in a plasmid in strain Zhang-LL was the inducer present in supernatant-MRS. This is the first report of the role of pediocin AcH in the quorum-sensing regulation of class II bacteriocin synthesis. The mRNA of the papA, papB, papC, and papD genes involved in bacteriocin synthesis by strain Zhang-LL in SM medium was upregulated significantly after being induced by pediocin AcH. This study offers the first evidence that the ABT40_05745, ABT40_05750, and ABT40_11975 components of two-component systems in L. plantarum subsp. plantarum Zhang-LL are involved in the induced regulation of AcH bacteriocin production. HIGHLIGHTS

Plantaricin BM-1, a class IIa bacteriocin produced by Lactobacillus plantarum BM-1, shows obvious antibacterial activity against Escherichia coli. However, the mechanism underlying the action of class IIa bacteriocins against gram-negative bacteria remains to be explored. The purpose of this study was to investigate the role of YbfA, a DUF2517 domain-containing protein, in the response of Escherichia coli K12 to plantaricin BM-1. The growth curve experiment and MIC experiment showed that the sensitivity of E. coli to plantaricin BM-1 was decreased by a ybfA null mutation. Electron microscopy showed that the ybfA null mutation reduced the surface rupture and contraction caused by plantaricin BM-1, and mitigated the effect of plantaricin BM-1 on the morphology of the E. coli cell membrane. Proteomics analysis showed that 323 proteins were differentially expressed in E. coli lacking the ybfA gene (P < 0.05); 118 proteins were downregulated, and 205 proteins were upregulated. The metabolic pathways containing the upregulated proteins mainly included outer membrane proteins, integral components of the plasma membrane, regulation of cell motility, and regulation of locomotion. The metabolic pathways involving the downregulated proteins mainly included outer membrane protein glycine betaine transport, amino-acid betaine transport, and transmembrane signaling receptor activity. The results of the proteomics analysis showed that the protein expression of the BasS/BasR two-component system was significantly increased (P < 0.05). Moreover, the expression levels of downstream proteins regulated by this two-component system were also significantly increased, including DgkA, FliC, and MlaE, which are involved in cell membrane structure and function, and RT-qPCR also confirmed this result. The growth curve showed that the sensitivity of E. coli to plantaricin BM-1 was significantly increased due to deletion of the BasS/BasR two-component system. Thus, deletion of ybfA in E. coli can increase the expression of the BasS/BasR two-component system and positively regulate the structure and function of the cell membrane to reduce the sensitivity to plantaricin BM-1. This will help to explore the mechanism of action of class IIa bacteriocins against gram-negative bacteria.

Probiotics can improve dyslipidemia and promote metabolic control as a therapeutic approach for type 2 diabetes mellitus (T2DM). The hypoglycemic effects of space-induced Lactobacillus plantarum SS18-5 on T2DM were explored in 4-week-old male Sprague Dawley rats. The normal (N) group was fed a basal diet, while the other groups received a high glucose fat diet. T2DM was established by streptozotocin injection and the T2DM rats were randomly divided into three groups, a diabetic (D) group (T2DM rats treated with saline only), GS18 group (T2DM rats treated with 109 CFU/ml of L. plantarum GS18), and SS18-5 group (T2DM rats treated with 109 CFU/ml of L. plantarum SS18-5). After continuous gavage for 6 weeks, blood biochemical indices were measured and livers were collected for histopathological examination. The colon contents were collected for counting of Escherichia coli, Clostridium perfringens, and Lactobacillus sp. The results showed that L. plantarum SS18-5 effectively controlled the weight of rats, reduced levels of fasting blood glucose, glycosylated hemoglobin, and insulin, increased liver glycogen levels, improved abnormal metabolism of blood lipids, enhanced the effect of anti-lipid peroxidation, alleviated chronic inflammation and fatty liver disease, and regulated the intestinal microbiota by reducing the numbers of E. coli and C. perfringens, and increasing the numbers of Lactobacillus sp. From these results, we conclude that space-induced L. plantarum SS18-5 has the potential to improve T2DM by alleviating hypoglycemia and regulating the intestinal microbiota. PRACTICAL APPLICATIONS: With the exploration of the universe, a large number of studies have observed the changes of microorganisms in space flight, which provided a new method for high-quality microbial pharmaceuticals in the space environment. In this study, the space environment mutated. Lactobacillus plantarum SS18-5 can effectively improve the blood glucose of rats with type 2 diabetes, relieve oxidative stress, reduce blood lipid content, enhance immune capacity, and regulate intestinal microflora, which has potential use in the treatment of type 2 diabetes.

In this study, an active antibacterial packaging film was developed by coating a polyethylene terephthalate/polyvinylidene chloride/retort casting polypropylene (PPR) plastic multilayer film with plantaricin BM‐1 and chitosan. The characteristics of the active packaging film and its antibacterial effect for chilled meat preservation were evaluated. Our results indicated that the barrier properties against oxygen were improved significantly and the tensile strength and the elongation at break were changed slightly. The active plantaricin film significantly (P

Bacillus subtilis SH21 was observed to produce an antifungal protein that inhibited the growth of F. solani. To purify this protein, ammonium sulfate precipitation, gel filtration chromatography, and ion-exchange chromatography were used. The purity of the purified product was 91.33% according to high-performance liquid chromatography results. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis and liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis revealed that the molecular weight of the protein is 30.72 kDa. The results of the LC–MS/MS analysis and a subsequent sequence-database search indicated that this protein was a chitosanase, and thus, we named it chitosanase SH21. Scanning and transmission electron microscopy revealed that chitosanase SH21 appeared to inhibit the growth of F. solani by causing hyphal ablation, distortion, or abnormalities, and cell-wall depression. The minimum inhibitory concentration of chitosanase SH21 against F. solani was 68 µg/mL. Subsequently, the corresponding gene was cloned and sequenced, and sequence analysis indicated an open reading frame of 831 bp. The predicted secondary structure indicated that chitosanase SH21 has a typical a-helix from the glycoside hydrolase (GH) 46 family. The tertiary structure shared 40% similarity with that of Streptomyces sp. N174. This study provides a theoretical basis for a topical cream against fungal infections in agriculture and a selection marker on fungi.