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Epidemiological evidence showed that patients suffering from obesity and T2DM are significantly at higher risk for chronic low-grade inflammation, oxidative stress, nonalcoholic fatty liver (NAFLD) and intestinal flora imbalance. Increasing evidence of pathological characteristics illustrates that some common signaling pathways participate in the occurrence, progression, treatment, and prevention of obesity and T2DM. These signaling pathways contain the pivotal players in glucose and lipid metabolism, e.g., AMPK, PI3K/AKT, FGF21, Hedgehog, Notch, and WNT; the inflammation response, for instance, Nrf2, MAPK, NF- kB, and JAK/STAT. Bioactive compounds from plants have emerged as key food components related to healthy status and disease prevention. They can act as signaling molecules to initiate or mediate signaling transduction that regulates cell function and homeostasis to repair and re-functionalize the damaged tissues and organs. Therefore, it is crucial to continuously investigate bioactive compounds as sources of new pharmaceuticals for obesity and T2DM. This review provides comprehensive information of the commonly shared signaling pathways between obesity and T2DM, and we also summarize the therapeutic bioactive compounds that may serve as anti-obesity and/or anti-diabetes therapeutics by regulating these associated pathways, which contribute to improving glucose and lipid metabolism, attenuating inflammation.

Aims A novel endolysin Salmcide-p1 was developed as a promising candidate of new preservative and a supplement to effective enzyme preparations against gram-negative bacterial contaminations. Methods and Results Salmcide-p1 was identified by complementing the genomic sequence of a virulent Salmonella phage fmb-p1. Salmcide-p1 of 112 μg ml−1 could quickly kill Salmonella incubated with 100 mmol l−1 EDTA, with no haemolytic activity. Meanwhile, Salmcide-p1 had a high activity of lysing Salmonella cell wall peptidoglycan. At different temperatures (4–75°C), pH (4–11) and NaCl concentration (10–200 mmol l−1), the relative activity of Salmcide-p1 was above 60%. At 4°C, the combination of Salmcide-p1 and EDTA-2Na could inhibit the number of Salmonella Typhimurium CMCC 50115 in skim milk to less than 4 log CFU ml−1 by 3 days, and the number of Shigella flexneri CMCC 51571 was lower than 4 log CFU ml−1 by 9 days. Conclusions Salmcide-p1 had a wide bactericidal activity against gram-negative bacteria and showed a broader anti-Salmonella spectrum than the phage fmb-p1. The combination strategy of Salmcide-p1 and EDTA-2Na could significantly inhibit the growth of gram-negative bacteria inoculated in skim milk. Significance and Impact of the Study Bacteriophage endolysin as an antibacterial agent is considered to be a new strategy against bacterial contamination.

Elastic well logs play an important role in reservoir characterization in the subsurface. However, due to the high expense of drilling, only a few wells are drilled to limited depths, making it difficult to understand the deposition and execute geophysical activities such as building background models for seismic inversion and property models for seismic forward modeling. We begin with P-velocity prediction between the wells and extension along the wellbore to tackle this problem. A hybrid workflow is introduced based on seismic and available P-velocity logs, including well-log decomposition, relative rock physics, seismic forward modeling, feature engineering based on seismic transform, optimal attribute selection, and machine learning network training and prediction. In this hybrid workflow, relative P-velocity instead of absolute P-velocity is used for labeling. The rock-physics study and seismic forward modeling contribute to label augmentation. The machine learning approach assists in discovering the relationship between the relative P-velocity and the optimal seismic attributes. Under physics rules, the predicted relative velocity through the trained network is integrated with the compaction trend to estimate the final absolute velocity. This hybrid workflow is applied to a case study of sand-shale sequences in northern China. The model-based deterministic inversion and data-driven machine learning approaches are also compared. The results of blind well testing indicate that the data-driven approach lacks generalization capability and fails to predict extension in some blind wells. The physics-based inversion performs differently in blind wells in different locations. By contrast, P-velocity prediction with the hybrid workflow improves prediction accuracy in all blind wells, horizontally and vertically. The results indicate that this hybrid workflow promises interpolating and extending elastic well logs when the deposition environment does not vary significantly. Further studies are recommended to discuss the applicability of this workflow.

Propionibacterium acnes plays a major role in acne vulgaris. In the pre-experiment, the growth of P. acnes was inhibited effectively using surfactin; however, the antibacterial mechanism has not been described. Therefore, the aim of this study was to evaluate antibacterial activity and analyse the mechanism of surfactin against P. acnes. Minimum inhibitory concentration, time-killing kinetics and scanning electron microscopy were used to evaluate the activity of surfactin against P. acnes, which showed that 128 μg ml-1 effectively inhibited growth. Cell wall permeability was evaluated by detecting the extracellular alkaline phosphatase activity, which increased to 1·83- and 2·32-fold after incubating with 128 and 256 μg ml-1 of surfactin for 10 h, respectively. Propidium iodide fluorescence, leakage of nucleic acid, protein, K+ , and Ca2+ , membrane potential and the leakage of calcein from small unilamellar vesicles all increased after incubation with surfactin, indicating that its strong biological activities act mainly by altering membrane integrity. In a mouse model of acne, surfactin significantly reduced P. acnes-induced epidermal swelling and erythema. These results indicate that surfactin effectively inhibited the growth of P. acnes by destroying the cell wall and membrane, and is a potential candidate for acne treatment.

The study was to optimize the separation procedures, characterize the galactoglycerolipids and explore their anti-inflammatory activities. Two monogalactosyldiacylglycerols (MGDGs) and three digalactosyldiacylglycerols (DGDGs) from

Although rennet is one of the best choices for cheese manufacturing, its production cannot meet the growing demands of the cheese industry. Thus, new milk-clotting enzymes (MCEs) with similar or better properties as/than those of calf chymosin are needed urgently. Here, three MCEs, BY-2, BY-3, and BY-4, were mined by bioinformatic analysis and then expressed in and isolated from Escherichia coli. BY-4 had the highest milk-clotting activity/proteolytic activity (238.76) with enzyme properties similar to those of calf chymosin. BY-4 cheese had a composition, appearance, consistency/texture, and overall acceptability proximate to calf chymosin cheese. The EC50 values of peptides extracted from BY-4 cheese for 2,2-diphenyl-1-picrylhydrazyl inhibition (antioxidant property), angiotensin-converting enzyme inhibition (antihypertensivity), and growth inhibition of liver cancer cells (antitumor property) were found to be 81, 49, and 238 μg/mL, respectively, which were 2.35, 2.59, and 2.12 folds higher than those of calf chymosin cheese. These results indicated the potential of BY-4 as a supplement to calf chymosin in cheese manufacturing, especially for functional and health care purposes.

The pyrroloquinoline quinone (PQQ)-dependent dehydrogenase DepA detoxifies deoxynivalenol (DON) by converting the C3-OH into a keto group. Herein, two crystal structures of DepA and its complex with PQQ were determined, together with biochemical evidence confirming the interactions of DepA with PQQ and DON and revealing a unique tyrosine residue important for substrate selection. Furthermore, four loops over the active site essential for DepA activity were identified, of which three loops were stabilized by PQQ, and the fourth loop invisible in both structures was considered important for binding DON, together constituting a lid for the active site. Preliminary engineering of the loop showed its potential for enzyme improvement. This study provides structural insights into how a PQQ-dependent dehydrogenase is equipped with the function of DON conversion and for the first time shows the necessity of a lid structure for PQQ-dependent dehydrogenase activity, laying foundation for structure-based design to enhance catalysis efficiency.

Pullulanase is a debranching enzyme that cleaves explicitly α-1,6 glycosidic bonds, which is widely used in starch saccharification, production of glucose, maltose, and bioethanol. The thermal-resistant pullulanase is isolated from a variety of microorganisms; however, the lack of industrial production of pullulanase has hindered the transformation of the laboratory to industry. In this study, the expensive maltose syrup and soybean meal powder were replaced with cheap corn starch and corn steep liquor, exhibiting 440 U/mL of pullulanase in shake flasks by changing the C/N value and the total energy of the medium. Subsequently, the cultivation conditions were explored in a 50-L and 50-m3 bioreactor. In batch culture, the pullulanase activity reached 896 U/mL, while it increased to 1743 U/mL in fed-batch culture by controlling the dissolved oxygen, pH, reducing sugar content, and temperature. Remarkably, the cultivation volume was enlarged to 50 m3 based on the technical parameters of fed-batch culture. The industrial production of pullulanase was successful, and the activity achieved 1546 U/mL. When the product was stored at room temperature (25 °C) for 6 months, the pullulanase activity was over 90%. The half-lives at 60 and 80 °C were 119.45 h and 51.18 h, respectively, which satisfied the industrial application requirements of pullulanase.

Plantaricin EmF separated and identified from

L-asparaginase (E.C.3.5.1.1) is a well-known agent that prevents the formation of acrylamide both in the food industry and against childhood acute lymphoblastic leukemia in clinical settings. The disadvantages of L-asparaginase, which restrict its industrial application, include its narrow range of pH stability and low thermostability. In this study, a novel L-asparaginase from Mycobacterium gordonae (GmASNase) was cloned and expressed in Escherichia coli BL21 (DE3). GmASNase was found to be a tetramer with a monomeric size of 32 kDa, sharing only 32% structural identity with Helicobacter pylori L-asparaginases in the Protein Data Bank database. The purified GmASNase had the highest specific activity of 486.65 IU mg−1 at pH 9.0 and 50 °C. In addition, GmASNase possessed superior properties in terms of stability at a wide pH range of 5.0–11.0 and activity at temperatures below 40 °C. Moreover, GmASNase displayed high substrate specificity towards L-asparagine with Km, kcat, and kcat/Km values of 6.025 mM, 11,864.71 min−1 and 1969.25 mM−1min−1, respectively. To evaluate its ability to mitigate acrylamide, GmASNase was used to treat potato chips prior to frying, where the acrylamide content decreased by 65.09% compared with the untreated control. These results suggest that GmASNase is a potential candidate for applications in the food industry.

Increasing cases of infections by foodborne pathogenic bacteria resulted in a great demand to find safe and novel antimicrobial compounds that can be used in the food industry. The isolation and ap...

In this study, to improve the thermal and mechanical properties of chitosan films, a chitosan/curdlan/carboxymethyl cellulose (CS/CD/CMC) ternary blended film was prepared and characterized. To prepare a uniform CS/CD/CMC ternary blended film, an effective method of blending CD with other materials was established as the following conditions: the ternary solution temperature was maintained at 60 °C, and the pH was controlled in the range from 12 to 4. Compared to the pure chitosan, the CS/CD/CMC blended films exhibited better mechanical properties, permeability, and thermal stability. In addition, visible light properties of the ternary blending film were improved. Scanning electron microscope and Fourier transform-infrared spectroscopy analyses indicated good compatibility among the CS, CD and CMC, which led to a corresponding improvement in the properties owing to interactions among the three components in the blending process. So, an effective method of blending CD with CS and CMC was established, and the blending film has good thermal and mechanical properties.

The use of natural preservatives has attracted considerable attention owing to their generally safe and environmentally friendly properties. In this study, we investigated the effects of t...

Deoxynivalenol (DON) is a potent mycotoxin produced by many Fusarium spp. that invade grains during the growth and storage seasons. Lactic acid bacteria have been reported to be capable of removing several toxins, thereby providing an effective detoxification method for possible contaminated substrates. The present study mainly focused on investigating the detoxification characteristics of DON by a Lactobacillus paracasei LHZ-1 strain, which was recently isolated from yogurt with a strong promise of removing DON from liquid culture. The results obtained showed that the cell wall of L. paracasei LHZ-1 can remove up to 40.7% of 50 μg/mL DON, whereas only 10.5 and 8.9% are removed by the culture supernatant or cellular lysate, respectively. Laser scanning confocal microscopy helped to identify the mechanism of DON detoxification by L. paracasei LHZ-1 through cellular adsorption, where DON was found to bind to the surface of bacterial cells to form complexes. In stability tests, about 39 or 99% of bound DON, either to viable bacterial cells or heat-inactivated cells, respectively, was released by methanol extractions, which indicated that the binding force between viable cells and DON could be stronger than it is in heat-inactivated cells. Adsorption kinetics demonstrated that approximately 33% of DON was removed within 20 h, with a maximum adsorption capacity of approximately 50.5 μg/mL in phosphate-buffered solution.

Biosurfactants are amphiphilic compounds that composed of hydrophilic and hydrophobic moieties, which possess the ability of self-organizing between phases, reducing the interfacial tension, and forming aggregates such as micelles. This spontaneous process results in significant changes in surface properties that directly influence the adherence of microorganisms. In this study, the ability of surfactin, a biosurfactant produced by Bacillus subtilis in reducing adhesion and disrupting the presence of biofilm of Staphylococcus aureus (S. aureus) on several surfaces, was investigated. Significant biofilm removal was observed on glass, polystyrene, and stainless steel surfaces. Furthermore, we explored the probable mechanism about how surfactin affected S. aureus biofilm formation. Based on our findings, surfactin had a significant effect on the polysaccharides production and especially decreased the percentage of alkali-soluble polysaccharide in biofilms. It also down-regulated the expression of icaA and icaD significantly, which are necessary for the important constituents to take shape of staphylococcal biofilm. In addition, it was found that the lipopeptide affected the quorum sensing (QS) system in S. aureus through regulating the auto inducer 2 (AI-2) activity, which has been reported to be negative for biofilm formation in S. aureus. These above properties could be applied in developing surfactin as a potential pre-coating agent on material surfaces to prevent S. aureus biofilm formation.

Water-extractable arabinoxylan (WEAX) is a pivotal component of wheat flour, which plays a positive role in bread making. In present study, the effect of recombinated Anabaena sp. Lipoxygenase (ana-rLOX) on the WEAX characteristics was evaluated. The results showed that ana-rLOX could effectively promote the oxidative crosslinking of the WEAX by acting as a free radical-generating agent and further elevated the particle size and viscosity of WEAX. The diferulic bridges induced by ana-rLOX could be formed through β-5'/α-O-4′, 5-5′ and 4-O-5′ bonds. The crosslinked WEAX by ana-rLOX were superior in improving fresh bread quality and delaying the staling behavior as compared with the addition of ana-rLOX or WEAX alone. These results showed that ana-rLOX could improve the fresh and aged bread quality by modifying the WEAX fractions.

Laccase from Streptomyces coelicolor (SLAC) can catalyze protein cross-linking without any phenolic acid assistance, and its effects on the solution and gel properties of whey protein isolate (WPI) were investigated in this study. WPI solution (5% w/v) was catalyzed by SLAC at 60 °C for 10 min at different enzymatic activities (0–20U). Results showed that, cross-linked by SLAC, the foaming capacity and emulsifying activity properties of WPI solution were improved. SLAC treated solutions had more negative charge in zeta potential, indicating more stable in protein solutions. SLAC-modified increased the apparent visicosities of WPI solutions. Rheological results showed that SLAC-treated WPI gels had higher dynamic storage modulus (G′) and took longer gelation time, compared to control (0U). SLAC treatment improved the strength of WPI gels and increased their water holding capacity (WHC). The results indicate that suitable SLAC catalysis could be used to modify whey protein isolate to improve its solution and gel properties.

In order to improve the cholesterol-binding capacity (CBC) of foxtail millet bran dietary fiber (FMBDF), xylanase-catalyzed hydrolysis was used. Single-factor experimental design and orthogonal experimental design were applied to optimize the hydrolysis conditions. The optimal hydrolysis conditions were as following: hydrolysis pH 3.8, xylanase dose 50 U/g FMBDF, hydrolysis temperature 50 °C and hydrolysis time 2 h. Under above conditions, the CBC value (11.57 mg/g) of the xylanase modified FMBDF (X-FMBDF) was 2.23 fold of FMBDF (5.19 mg/g). Analysis of monosaccharide composition, infrared spectrum and scanning electron microscopy showed that xylanase treatment could change the monosaccharide composition and microstructure of FMBDF, which contributed to the binding of dietary fiber to cholesterol. It was suggested that enzymatic treatment was a good method to modify the functional properties of dietary fibers.

Bacteriocins are useful for controlling the composition of microorganisms in fermented food. Bacteriocin synthesis is regulated by quorum sensing mediated by autoinducing peptides. In addition, short-chain fatty acids, especially acetic acid, reportedly regulate bacteriocin synthesis. Five histidine kinases that regulated the synthesis of bacteriocins were selected to verify their interactions with acetate. Acetate activated the kinase activity of PlnB, SppK, and HpK3 in vitro and increased the yield of their cognate bacteriocins plantaricin EF, sakacin A, and rhamnosin B in vivo. The antimicrobial activity against Staphylococcus aureus of the fermentation supernatants of Lactobacillus plantarum, Lactobacillus sakei, and Lactobacillus rhamnosus with addition of acetate increased to 298%, 198%, and 289%, respectively, compared with that in the absence of acetate. Our study elucidated the activation activity of acetate in bacteriocin synthesis, and it might provide a potential strategy to increase the production of bacteriocin produced by Lactobacillus. IMPORTANCE Bacteriocins produced by lactic acid bacteria (LAB) are particularly useful in food preservation and food safety. Bacteriocins might increase bacterial competitive advantage against the indigenous microbiota of the intestines; at the same time, bacteriocins could limit the growth of undesired microorganisms in yogurt and other dairy products. This study confirmed that three kinds of histidine kinases were activated by acetate and upregulated bacteriocin synthesis both in vitro and in vivo. The increasing yield of bacteriocins reduced the number of pathogens and increased the number of probiotics in milk. Bacteriocin synthesis activation by acetate may have a broad application in the preservation of dairy products and forage silage.

Although rennet is one of the best choices for cheese manufacturing, its production cannot meet the growing demands of the cheese industry. Thus, new milk-clotting enzymes (MCEs) with similar or better properties as/than those of calf chymosin are needed urgently. Here, three MCEs, BY-2, BY-3, and BY-4, were mined by bioinformatic analysis and then expressed in and isolated from

The synthesis of plantaricin in Lactobacillus plantarum is regulated by quorum sensing. However, the nature of the extra-cytoplasmic (EC) sensing domain of the histidine kinase (PlnB1) and the ability to recognize the auto-inducing peptide PlnA1 is not known. We demonstrate the key motif Ile-Ser-Met-Leu of auto-inducing peptide PlnA1 binds to the hydrophobic region Phe-Ala-Ser-Gln-Phe of EC loop 2 of PlnB1 via hydrophobic interactions and hydrogen bonding. Moreover, we identify a new inducer, acetate, that regulates the synthesis of plantaricin by binding to a positively charged region (Arg-Arg-Tyr-Ser-His-Lys) in loop 4 of PlnB1 via electrostatic interaction. The side chain of Phe143 on loop 4 determined the specificity and affinity of PlnB1 to recognize acetate. PlnA1 activates quorum sensing in log phase growth and acetate in stationary phase to maintain the synthesis of plantaricin under conditions of reduced growth. Acetate activation of PlnB was also evident in four types of PlnB present in different Lb. plantarum strains. Finally, we proposed a model to explain the developmental regulation of plantaricin synthesis by PlnA and acetate. These results have potential applications in improving food fermentation and bacteriocin production.

Enterohaemorrhagic Escherichia coli (EHEC) is a prominent foodborne pathogen that causes infectious intestinal diarrhoea. Lactobacillus is a recognized probiotic that inhibits intestinal pathogens and maintains the balance of the intestinal flora. The purpose of this study was to investigate the regulatory effects of three Lactobacillus strains, L. johnsonii, L. plantarum, and L. rhamnosus, on the intestinal flora of EHEC-infected mice. The initial weight and diarrhoea index of the mice were recorded. After 21 days, the faeces of the mice were subjected to 16S rDNA high-throughput sequencing. The diarrhoea index of mice treated with Lactobacillus improved, their body weight continued to rise, and their liver index gradually decreased. The α diversity analysis showed that the intestinal flora diversity and abundance were lower in mice infected with EHEC than in healthy mice. L. plantarum, L. johnsonii, and L. rhamnosus significantly improved the diversity of the flora species. In terms of flora composition, the three main phyla present were Bacteroidetes, Firmicutes, and Proteobacteria. The abundance of these three phyla was reduced to 93.81% after infection and restored to over 96.30% after treatment. At the genus level, Lactobacillus reduced the abundance of Bacteroides, Helicobacter pylori, and Shigella, while increasing the abundance of butyric acid-producing bacteria and Lactobacillus. Finally, a heat map and non-metric multidimensional scaling analysis showed that the intestinal flora structures in the L. johnsonii, L. plantarum, and L. rhamnosus treatment groups were closest to those of healthy mice. In conclusion, L. johnsonii, L. plantarum, and L. rhamnosus regulated and improved the structure of intestinal flora and relieved diarrhoea caused by EHEC infection.

A described monogalactosyldiacylglycerol (MGDG) and two undescribed digalactosyldiacylglycerols (DGDGs) were isolated from the leaves of Perilla frutescens (L.) Britton (Labiatae) by using silica gel column chromatography and semi-preparative high performance liquid chromatography. The elucidation of complete structure of these compounds were conducted by using MS and NMR techniques. The MGDG (7.5% of total lipids) was identified as 1,2-2-O-(9Z,12Z,15E-octadecatrienoyl)-3-O-(β-D-galactopyranosyl)-sn-glycerol. The two DGDGs (2.8% and 1.0% of total lipids, respectively) were identified as 1-O-(9Z,12Z,15Z-octadecatrienoyl)-2-O-(6Z,9Z,12Z-octadecatrienoyl)-3-O-[β-D-galactopyranosyl-(1″→6′)-α-D-galactopyranosyl]-sn-glycerol and 1-O- hexadecanoyl -2-O-(9Z,12Z,15Z-octadecatrienoy -l)-3-O-[β-D-galactopyranosyl-(1″→6′)-α-D-galactopyranosyl]-sn-glycerol, respectively. All the isolated MGDG and DGDGs were evaluated for their anti-inflammatory activities in lipopolysaccharide (LPS)-stimulated murine macrophages RAW264.7 cells. All of them showed good inhibitory activities and significantly blocked the production of LPS-induced TNF-α, (IL)-1β and IL-6. The above results shed some light on a better understanding of the traditional anti-inflammatory effect of Perilla frutescens and reveal the potential anti-inflammatory constituents.

Methicillin-resistant Staphylococcus aureus (MRSA) poses great threats to human health. In this research, we found that the newly discovered bacteriocin plantaricin GZ1-27 could efficiently inhibit the MRSA, with a MIC of 32 μg/mL. Comprehensive investigations were carried out by analysis of K

Increasing cases of infections by S. aureus in food resulted in a great demand to utilize natural, safe, and effective antimicrobial agents which could inactivate foodborne pathogens in the food industry. A novel class IId bacteriocin, plantaricin 827, produced by Lactobacillus plantarum 163 was isolated and identified. Its molecular mass and amino acid sequence were determined to be 827 Da and N-His-Ser-Ser-Tyr-Gly-Tyr-Asp-OH, respectively. Plantaricin 827 not only possesses thermostable and pH adaptability but also shows a broader antibacterial spectrum. Its antibacterial mechanism against S. aureus increased the cell membrane permeability and integrity, resulting in the leakage of K+ and changes in cell morphology. Meanwhile, it inhibited the biofilm formation and interacted with genomic DNA minor groove in AT-rich regions. In addition, plantaricin 827 could significantly inactivate S. aureus in skim milk and extend the shelf life of milk. These results demonstrated that plantaricin 827 could effectively inhibit S. aureus and show the potential to replace chemical preservatives to control foodborne pathogens in dairy products.

Although application of organic fertilizers has become a recommended way for developing sustainable agriculture, it is still unclear whether above-ground and below-ground crops have similar responses to chemical fertilizers (CF) and organic manure (OM) under the same farming conditions. The current study investigated soil quality and crop yield response to fertilization of a double-cropping system with rapeseed (above-ground) and sweet potato (below-ground) in an infertile red soil for 2 years (2014–16). Three fertilizer treatments were compared, including CF, OM and organic manure plus chemical fertilizer (MCF). Organic fertilizers (OM and MCF) increased the yield of both above- and below-ground crops and improved soil biochemical properties significantly. The current study also found that soil-chemical properties were the most important and direct factors in increasing crop yields. Also, crop yield was affected indirectly by soil-biological properties, because no significant effects of soil-biological activities on yield were detected after controlling the positive effects of soil-chemical properties. Since organic fertilizers could not only increase crop yield, but also improve soil nutrients and microbial activities efficiently and continuously, OM application is a reliable agricultural practice for both above- and below-ground crops in the red soils of China.

Background Plipastatin, an antifungal lipopeptide, is synthesized by a non-ribosomal peptide synthetase (NRPS) in Bacillus subtilis. However, little information is available on the combinatorial biosynthesis strategies applied in plipastatin biosynthetic pathway. In this study, we applied module or individual domain deletion strategies to engineer the plipastatin biosynthetic pathway, and investigated the effect of deletions on the plipastatin assembly line, as well as revealed the synthetic patterns of novel lipopeptides. Results Module deletion inactivated the entire enzyme complex, whereas individual domain (A/T domain) deletion within module 7 truncated the assembly line, resulting in truncated linear hexapeptides (C16~17β-OHFA-Glu-Orn-Tyr-Thr-Glu-Ala/Val). Interestingly, within the module 6 catalytic unit, the effect of thiolation domain deletion differed from that of adenylation deletion. Absence of the T6-domain resulted in a nonproductive strain, whereas deletion of the A6-domain resulted in multiple assembly lines via module-skipping mechanism, generating three novel types of plipastatin derivatives, pentapeptides (C16~17β-OHFA-Glu-Orn-Tyr-Thr-Glu), hexapeptides (C16~17β-OHFA-Glu-Orn-Tyr-Thr-Glu-Ile), and octapeptides (C16~17β-OHFA-Glu-Orn-Tyr-Thr-Glu-Gln-Tyr-Ile). Conclusions Notably, a unique module-skipping process occurred following deletion of the A6-domain, which has not been previously reported for engineered NRPS systems. This finding provides new insight into the lipopeptides engineering. It is of significant importance for combinatorial approaches and should be taken into consideration in engineering non-ribosomal peptide biosynthetic pathways for generating novel lipopeptides. Electronic supplementary material The online version of this article (10.1186/s12934-018-0929-4) contains supplementary material, which is available to authorized users.

Bacillus cereus is an opportunistic pathogen that causes foodborne diseases. We isolated a novel bacteriocin, designated plantaricin GZ1-27, and elucidated its mode of action against B. cereus. Plantaricin GZ1-27 was purified using ammonium sulfate precipitation, gel-filtration chromatography, and RP-HPLC. MALDI-TOF/MS revealed that its molecular mass was 975 Da, and Q-TOF-MS/MS analysis predicted the amino acid sequence as VSGPAGPPGTH. Plantaricin GZ1-27 showed thermostability and pH stability. The antibacterial mechanism was investigated using flow cytometry, confocal laser-scanning microscopy, scanning and transmission electron microscopy, and RT-PCR, which revealed that GZ1-27 increased cell membrane permeability, triggered K+ leakage and pore formation, damaged cell membrane integrity, altered cell morphology and intracellular organization, and reduced the expression of genes related to cytotoxin production, peptidoglycan synthesis, and cell division. These results suggest that plantaricin GZ1-27 eff...

Listeria monocytogenes serotype 1/2a is considered as a foodborne pathogen, resulting in high morbidity. Detection of Listeria monocytogenes serotype 1/2a is rather difficult and time-consuming thus, the need for better detection methods is encouraged. In order to rapidly detect and identify L. monocytogenes serotype 1/2a, specific target genes were mined by the comparative genomics approach. Three specific primers based on novel specific targets were screened. The primers were m2a1, m2a4, and m2a8. The m2a4 primer was the most sensitive and stable among the three. A multiplex PCR method for detecting 1/2a serotype was developed by combining the serotype-specific primer m2a4 and species-specific primer Lm8 of gene LMOf2365_2721. The detection limit of the multiplex PCR was 305.5 fg/μL for genomic DNA and 8.6 × 103 cfu/mL for L. monocytogenes serotype 1/2a, respectively. And the primers for the detection of L. monocytogenes serotype 1/2a was not interfered by genome DNA of other L. monocytogenes serotypes 1/2b, 1/2c, 3a, 4b in different concentrations. The artificially contaminated milk with L. monocytogenes serotype 1/2a of 8.6 × 104–8.6 × 100 cfu/10 mL could be detected successfully with the multiplex PCR method after 6–12 h of enrichment. These results suggested that the multiplex PCR assay was able to rapidly detect and identify L. monocytogenes serotype 1/2a and exhibited high specificity and sensitivity. Therefore, the detection process of the serotype 1/2a in food could be accomplished at less than 8.6 × 104 cfu/10 mL of contamination in 9–15 h.

The antibacterial activity and mechanism of monolauroyl-galactosylglycerol (MLGG) against Bacillus cereus were investigated. The minimum inhibitory concentration of MLGG against B. cereus was 0.156 mg/ml. The inhibition growth curve assay also revealed that MLGG presented good antibacterial activity against B. cereus. Alkaline phosphatase activity assay, nucleotide leakage and cell viability analysis demonstrated that MLGG disrupted the integrity of cell wall and cell membrane of B. cereu s. Scanning electron microscopy and transmission electron microscopy results showed obvious morphological and ultrastructural changes of B. cereu s membrane, further confirming the damage of cell membrane integrity caused by MLGG. In summary, MLGG might exerted its antibacterial activity mainly by an action mode of membrane disruption, and it was expected to be an alternative for the development of new food preservatives.

LI-F type peptides are a family of cyclic lipodepsipeptide antibiotics isolated from Paenibacillus polymyxa and display potent activities against positive bacteria including methicillin-resistant S. aureus (MRSA). In this study, we investigated the mechanism of action of LI-F type peptide AMP-jsa9 against a MRSA (S. aureus CICC10790), which is resistant to ciprofloxacin, gentamicin, kanamycin, chloramphenicol, methicillin, and tetracycline. It was found that AMP-jsa9 mainly targets the cell membrane of MRSA and is able to inhibit biofilm formation through killing planktonic bacteria cells. Moreover, AMP-jsa9 can bind to DNA in vitro, which represents another pathway for the action on MRSA. Furthermore, in vivo treatment of scalded mice with AMP-jsa9 resulted in inhibiting MRSA infections and healing of the scalded wound. In addition, it was demonstrated that AMP-jsa9 can effectively inhibit MRSA infections in scalded murine epidermis and that inflammatory cytokines including IL-8, IL-6, tumor necrosis factor alpha (TNF-α), and monocyte chemotactic factor-1 (MCP-1) were reduced; moreover, both protein and gene expression levels of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (e-NOS) were enhanced, which promote neovascularization and proliferation of new granulation tissue.

Agricultural byproduct-foxtail millet (Setaria italic) bran was explored to extract dietary fiber by enzymatic methods and the physicochemical and functional properties of foxtail millet bran dietary fiber (FMBDF) were investigated. Results revealed that foxtail millet bran was a good source for dietary fiber production. The studies of physicochemical and functional properties showed that the water holding capacity and swelling power of FMBDF were 3.24 g/g and 2.06 ml/g, respectively. Meanwhile, FMBDF exhibited good adsorption capacities to lipophilic substances such as lard (3.34 g/g), peanut oil (2.32 g/g) and cholesterol (5.19 mg/g). Its bile salts adsorption capacity (143.03 μmol/g for sodium cholate and 76.65 μmol/g for sodium taurocholate) indirectly reflected its cholesterol-lowering effect. The chemical composition and microstructure studies of FMBDF demonstrated that these had a lot to do with its functional properties. The results indicate that FMBDF has a great potential to be used as functional ingredient in food products.

The gene encoding a novel acidic lipoxygenase from Myxococcus xanthus DK1622 (accession: WP_011551853.1) was cloned into vector pET-28a and expressed in Escherichia coli BL21(DE3). The recombinant enzyme (rMxLOX), with a molecular weight of approximately 80 kDa, was purified to homogeneity using one-step nickel-affinity chromatography and showed an activity of 5.6 × 104 U/mg. The optimum pH and temperature for rMxLOX activity were found to be 3.0 and 30 °C, respectively. Purified rMxLOX exhibited activity towards linoleic acid and arachidonic acid as substrates, with linoleic acid being the better substrate (Km and kcat values of 0.048 mM and 13.3/s, respectively). The synthetic dye aniline blue was decolorized 69.7 ± 3.5%, following incubation with rMxLOX for 35 min. These results reveal the potential for the use of rMxLOX in the pulp, textile, and wastewater treatment industries.