Pediocin AcH Is Transcriptionally Regulated by a Two-Component System in Lactobacillus plantarum subsp. plantarum.

ABSTRACT: 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.

Identifying the effective phosphorous species over modified P-ZSM-5 zeolite: a theoretical study.

In this work, a density functional theory (DFT) study was carried out to address the fundamental description of the effective phosphorous species that could improve the framework stability and reduce the coke deposition formation on the P-ZSM-5 zeolite. On the basis of the dealumination barriers of ZSM-5 with all the possible phosphorous species bound on the zeolite framework, PO4H4 was ascertained to be the effective phosphorous species that could improve the ZSM-5 zeolite hydrothermal stability and reduce its acid strength. Apart from this, the olefin polymerization reaction is the main cause of coking deactivation for ZSM-5. Thus, the effect of the modification P-ZSM-5 on the reactivity of light olefins dimerization was also studied. Compared to the unmodified ZSM-5, the activation energy of the rate-limiting step of ethylene dimerization was increased from 20.3 kcal mol-1 to 34.6 kcal mol-1, thereby apparently inhibiting ethylene dimerization and improving the resistance to coke deposition for P-ZSM-5. Our calculation results should provide a beneficial theoretical guide for designing and improving a catalyst for the methanol-to-olefins process and bioethanol dehydration.

Development and antilisterial activity of PE-based biological preservative films incorporating plantaricin BM-1.

In recent years, bacteriocin, as a natural antimicrobial compound, provides enormous promise to be used in food safety preservation. In this work, the polyethylene(PE)-based biological preservative films incorporating plantaricin BM-1, a typical IIa bacteriocin produced by Lactobacillus plantarum BM-1, were developed and characterized. The results showed that PE, low-density PE (LDPE) and high-density PE (HDPE) films soaked in plantaricin BM-1 solution had obvious antimicrobial activities against Listeria monocytogenes. And the volume of plantaricin BM-1 solution absorbed by PE, LDPE and HDPE films continued to increase and reached the maximum during exposure for up to 10, 6 and 16 h, respectively. And the maximum absorption volumes of plantaricin BM-1 solution had no significant difference (P > 0.05) between the PE, LDPE and HDPE films. When soaking in water, the release amount of plantaricin BM-1 from active PE, LDPE and HDPE films reached the maximum potency at 16, 12 and 20 h, respectively. And the maximum release amount of plantaricin BM-1 from PE and LDPE active films was dramatically more than the HDPE active film (P < 0.05). Moreover, the inhibitory effect of active films incorporating plantaricin BM-1 maintained stability for at least 120 days against L. monocytogenes stored at 25°C, which suggest a potential application of the biological preservative films on the control of foodborne pathogen L. monocytogenes.

Conditions optimising on the yield of biomass, total lipid, and valuable fatty acids in two strains of Skeletonema menzelii.

Polyunsaturated fatty acids (PUFA) and eicosapentaenoic acid (EPA) are essential for the health of aquaculture organisms and human beings. A total of 9 species of diatoms were screened and two strains of Skeletonema menzelii were selected for further study due to their high growth rates, PUFA and EPA contents. The culture conditions for the yield of biomass, total lipid, EPA and PUFA were optimised. The quickest growth rates (0.28-0.41d(-1)) were achieved with moderate supplement of nitrogen, phosphorus, iron and silicon. The accumulation of total lipid (17.85-22.70% of dry weight) benefitted from deprivation of nitrogen, phosphorus and silicon, but a moderate iron supplement. Highest PUFA (38.26-50.48% of total fatty acids) or EPA (14.26-18.39% of total fatty acids) contents were observed under high nitrogen and phosphorus supplement, moderate available iron but deprivation of silicon. These findings make tangible contributions to culture S. menzelii for commercial production of PUFA or EPA.

Hypocholesterolemic effects of Kluyveromyces marxianus M3 isolated from Tibetan mushrooms on diet-induced hypercholesterolemia in rat.

To investigate the effects of Kluyveromyces marxianus M3 isolated from Tibetan mushrooms on diet-induced hypercholesterolemia in rats, female Wistar rats were fed a high-cholesterol diet (HCD) for 28 d to generate hyperlipidemic models. Hyperlipidemic rats were assigned to four groups, which were individually treated with three different dosages of K. marxianus M3+HCD or physiological saline+HCD via oral gavage for 28 d. The total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels in the serum and liver of the rats were measured using commercially available enzyme kits. In addition, the liver morphology was also examined using hematoxylin and eosin staining and optical microscopy. According to our results, the serum and liver TC, TG, LDL-C levels and atherogenic index (AI) were significantly decreased in rats orally administered K. marxianus M3 (p <0.01), and the HDL-C levels and anti atherogenic index (AAI) were significantly increased (p <0.01) compared to the control group. Moreover, K. marxianus M3 treatment also reduced the build-up of lipid droplets in the liver and exhibited normal hepatocytes, suggesting a protective effect of K. marxianus M3 in hyperlipidemic rats.

Hypocholesterolemic effects of Kluyveromyces marxianus M3 isolated from Tibetan mushrooms on diet-induced hypercholesterolemia in rat

To investigate the effects of Kluyveromyces marxianus M3 isolated from Tibetan mushrooms on diet-induced hypercholesterolemia in rats, female Wistar rats were fed a high-cholesterol diet (HCD) for 28 d to generate hyperlipidemic models. Hyperlipidemic rats were assigned to four groups, which were individually treated with three different dosages of K. marxianus M3+HCD or physiological saline+HCD via oral gavage for 28 d. The total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels in the serum and liver of the rats were measured using commercially available enzyme kits. In addition, the liver morphology was also examined using hematoxylin and eosin staining and optical microscopy. According to our results, the serum and liver TC, TG, LDL-C levels and atherogenic index (AI) were significantly decreased in rats orally administered K. marxianus M3 (p <0.01), and the HDL-C levels and anti atherogenic index (AAI) were significantly increased (p <0.01) compared to the control group. Moreover, K. marxianus M3 treatment also reduced the build-up of lipid droplets in the liver and exhibited normal hepatocytes, suggesting a protective effect of K. marxianus M3 in hyperlipidemic rats.

Microbial floral dynamics of Chinese traditional soybean paste (doujiang) and commercial soybean paste.

Traditional soybean paste from Shandong Liangshan and Tianyuan Jiangyuan commercial soybean paste were chosen for analysis and comparison of their bacterial and fungal dynamics using denaturing gel gradient electrophoresis and 16S rRNA gene clone libraries. The bacterial diversity results showed that more than 20 types of bacteria were present in traditional Shandong soybean paste during its fermentation process, whereas only six types of bacteria were present in the commercial soybean paste. The predominant bacteria in the Shandong soybean paste were most closely related to Leuconostoc spp., an uncultured bacterium, Lactococcus lactis, Bacillus licheniformis, Bacillus spp., and Citrobacter freundii. The predominant bacteria in the Tianyuan Jiangyuan soybean paste were most closely related to an uncultured bacterium, Bacillus licheniformis, and an uncultured Leuconostoc spp. The fungal diversity results showed that 10 types of fungi were present in the Shandong soybean paste during the fermentation process, with the predominant fungi being most closely related to Geotrichum spp., an uncultured fungal clone, Aspergillus oryzae, and yeast species. The predominant fungus in the commercial soybean paste was Aspergillus oryzae.

A solid-state NMR study of structure and segmental dynamics of poly(propylmethacryl-heptaisobutyl-pss)-co-styrene nanocomposites.

The domain structure and mobility of poly(propylmethacryl-heptaisobutyl-pss)-co-styrene nanocomposites with different polyhedral oligomeric silsesquioxane (POSS) contents were investigated by various solid-state NMR techniques in combination with XRD. The NMR relaxation time measurements suggested that increasing POSS content trended to mobilize the chains in PS unit. Although XRD results showed that POSS was well dispersed into the polymer matrix, 2D WISE NMR indicated that the dispersion of POSS into the polymer matrix led to a composite structure composed of rigid and densely packed PS domain and mobile and amorphous POSS domain. This implied that the size of the two domains was very small. 2D HETCOR NMR implied that the distance between PS network and POSS unit gradually decreased when the POSS content successively increased. The dispersed POSS domain size determined by 2D spin-diffusion NMR experiments was increased with the POSS loading, being about 3.0, 3.9, 6.0 nm for the POSS15, POSS25 and POSS45 nanocomposites, respectively.

Anomalous diffusion of chains in semicrystalline ethylene polymers.

The chain diffusion between crystalline and amorphous/interfacial regions in semicrystalline ethylene homo- and copolymers was investigated by means of solid-state NMR. It was found that the crystalline chain segment diffusion along the chain-folded path is anomalous and can be characterized by the scaling relation of mean-square displacement, approximately t(1/2).

[Application of gyrB in the identification of closely related bacteria-- a review].

The single-copied gyrB gene, encoding the subunit B of gyrase and distributing universally in all bacteria, has the average substitution rate of 0.7%-0.8% per million years. It's proved that this region could be used to discriminate and identify the closely related species of different bacteria such as Pseudomonoas, Bacillus, Vibrio, Enterobacteriaceae, Mycobacteria, Aeromonas, Lactic acid bacteria et.al. It also can be used of quantitative or restriction fragment analysis of bacteria with the aid of species-specific primers or combined with DGGE (denaturing gradient gel electrophoresis). It really brings new promise for the identifying closest isolates or fingerprinting population due to overcoming the shortage of undistinguishing them acutely with the non-protein-encoding genes such as 16S rDNA or ITS (internal transcribed spacer) DNA. It's an important new molecular marker for researches of closely related species and becoming an attractive topic in current microbial research world.

[Effects of a lactic acid bacteria community SFC-2 treated on rice straw].

Aimed to utilize rice straw and lessen the pressure of environment, the rice straw was used as the fermentation material, and a lactic acid bacteria community SFC-2 from my laboratory was inoculated into the rice straw to investigate the inoculation effects. After 30 days fermentation, the inoculated fermented straw smelt acid-fragrant, and the pH value was 3.8, which was lower than the control of 4.1. Furthermore, lactic acid concentration was more than that in the control. Especially L-lactic acid concentration was two times more than in the control, and the crude protein content was 10.16% higher than that in the control, and the crude fiber content was 3.2% lower than that in the control. From the patterns of denaturing gradient gel electrophoresis (DGGE), Lactobacillus plantarum, Lactobacillus fermentum and Lactobacillus paracasei rapidly became the advantageous species in the inoculated straws. However, Enterobacter sakazakii, Pantoea agglomerans, Enterobacter endosymbiont, Pantoea ananatis, whichwere predominate in the controls, were not detected in the inoculated straws, and the fermented quality was improved significantly.

[Microbial dynamics during the composting process].

Microbial dynamics of microbial community during the composting process was investigated with the methods of denaturing gradient gel electrophoresis (DGGE) and plating. The results showed that the most of microorganism count was bacterium, the second was actinomycete and the least was fungi. At the same time, the count of the thermophilic microorganism was always less than that of the mesophilic during the composting process. The count of mesophilic microorganism at later stage was less than that at the initial stage. However, the count of thermophilic antinomycete and fungi at later stage were more than that at initial stage, and the count of thermophilic bacterium was stable throughout the composting process. The bands pattern of DGGE and 16S rDNA analyses indicated that bacterial succession was presented during the composting process. The genera of Bdellovibrio, Clostridia bacterium and Bacillus were dominant species at initial stage (before the first 15 days), and Beta proteobacterium, Petrobacter succinimandens, Nitrospirae bacterium and Paenibacillus were dominant species at middle and later stage. Moreover, Clostridium was found throughout the process.

[Effects of mitomycin C on the expression and transport of ice-nuclei proteins of Erwinia herbicola].

Abstract: In this paper, Mitomycin C (MMC) was added to different kinds of medium to study the effects of different cultural conditions on the Erwinia herbicola 10025A. For the first time it was confirmed that the expressed activity of the ice-nuclei active protein was different from its transportable manner from the ice nucleation active bacteria (Erwinia herbicola 10025A). The findings indicated that MMC could stimulate the SOS response,and induce the synthesis of some enzymes and proteins, which take part in repairing the damaged DNA. The effects of the MMC on the E. herbicola under different media were different. It could increase the ice nucleation activity of the E. herbicola, forming new small vesicles, which are secreted to the outside of membrane. The importance of this research for study the living mechanism of cells ander poor condition was discussed.