Zhaoxin Lu

Study on the antibiotic activity of microcapsule curcumin against foodborne pathogens

Curcumin as an edible natural pigment has several biological activities but its use as a food colorant and preservative is restricted due to low stability and insolubility in water. Stabilizing it with microencapsulation to obtain microcapsule curcumin can improve its stability and solubility. The microcapsule curcumin was studied for their antibacterial and antifungal activities against some foodborne pathogens and spoilage microbe such as Escherichia coli, Yersinia enterocolitica, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Aspergillus niger, Penicllium notatum, and Saccharomyces cerevisiae. It exhibited broad spectrum inhibitory effect against all organisms by Oxford cup methods, and its minimum inhibitory concentrations (MIC) were determined by agar dilution method and ranged from 15.7 to 250 microg/mL. For the selected microorganisms, its antibacterial activity was more pronounced against Gram-positive bacteria than Gram-negative bacteria. Furthermore, its antifungal activity is much better than antibacterial activity. Microcapsule curcumin remains in antibacterial and antifungal activities after microencapsulation, which can be potential colorant and preservative in food industry.

Production of γ-aminobutyric acid by Streptococcus salivarius subsp. thermophilus Y2 under submerged fermentation

Summary.γ-Aminobutyric acid (GABA), a major inhibitory neurotransmitter in the central nervous system, has several well-known physiological functions and has been applied to the production of many drugs and functional foods. The technology of GABA production via submerged fermentation by Streptococcus salivarius subsp. thermophilus Y2 was investigated in this paper. It indicated that the GABA production was related to the biochemical characteristics of glutamate decarboxylase (GAD) of S. salivarius subsp. thermophilus Y2. After 24 h of fermentation at 37 °C, which is the suitable culture conditions for GAD-production, then the culture condition were adjusted to the optimal temperature (40 °C) and pH (4.5) for the GAD reaction activity in biotransformation of cells and pyridoxal 5′-phosphate (0.02 mmol/l) were added to the broth at the 48 h, the GABA production was increased up to 1.76-fold, reaching 7984.75 ± 293.33 mg/l. The strain shows great potential use as a starter for GABA-containing yoghurt, cheese and other functional fermented food productions.

A Newly Isolated Organic Solvent Tolerant Staphylococcus saprophyticus M36 Produced Organic Solvent-Stable Lipase

Thirty-eight high lipase activity strains were isolated from soil, seawater, and Brassica napus. Among them, a novel organic solvent tolerant bacterium (strain M36) was isolated from the seawater in Jiangsu, China. Isolate M36 was able to grow at high concentration of benzene or toluene up to 40% (vol/vol), and later identified as Staphylococcus saprophyticus by biochemical test and 16s ribosomal DNA sequence. No work on Staphylococcus producing lipase with organic solvent tolerance has been reported so far. The lipase of strain M36 whose activity in liquid medium was 42 U mL−1 at 24-h incubation time was stable in the presence of 25% (vol/vol) p-xylene, benzene, toluene, and hexane.

Identification of fengycin homologues from Bacillus subtilis with ESI-MS/CID

Bacillus subtilis fmbJ (CGMCC no.0943) was used to produce lipopeptides antibiotics fengycin. The fengycin mixture was precipitated with 6N HCl and extracted by methanol. Electrospray ionization mass spectrometry/collision-induced dissociation (ESI-MS/CID) were used to analyze the fengycin mixture. In the ESI-MS/CID spectra of fengycin molecular ions, production ions (m/z 1080, m/z 966, m/z 1108 and m/z 994) were always detected. Therefore, these production ions (m/z 1080, m/z 966, m/z 1108 and m/z 994) could be used as fingerprints to quickly detect fengycin A and fengycin B. By the method of ESI-MS/CID, six homologues of fengycin A with C14 to 19 and four homologues of fengycin B with C14 to 17 were characterized. The method will be useful for rapidly determining whether a strain produces fengycin homologues.

A simple method for the simultaneous decoloration and deproteinization of crude levan extract from Paenibacillus polymyxa EJS-3 by macroporous resin.

A simple method for the simultaneous decoloration and deproteinization of crude levan extract from the endophytic bacterium Paenibacillus polymyxa EJS-3 was developed through static and dynamic adsorption tests of macroporous resins. S-8 resin demonstrated the highest decoloration and deproteinization ratios among various resins tested. Under optimized static adsorption conditions (pH 6.0, 35 degrees C and adsorption time of 70 min), the ratios of decoloration, deproteinization and polysaccharide recovery for S-8 resin were 76.8%, 78.9% and 69.0%, respectively. Under optimized dynamic adsorption condition (flow rate of 2 BV/h, 160 ml of 2.5mg/ml crude levan extract), higher ratios of decoloration, deproteinization and polysaccharide recovery for S-8 resin (84.6%, 91.7% and 81.3%, respectively) were observed. The method developed will provide a potential approach for large-scale production of levan from P.polymyxa EJS-3.

Purification and Characterization of Plantaricin 163, a Novel Bacteriocin Produced by Lactobacillus plantarum 163 Isolated from Traditional Chinese Fermented Vegetables

Presumptive lactic acid bacteria (LAB) strains isolated from traditional Chinese fermented vegetables were screened for bacteriocin production. A novel bacteriocin-producing strain, Lactobacillus plantarum 163, was identified on the basis of its physiobiochemical characteristics and characterized by 16S rDNA sequencing. The novel bacteriocin, plantaricin 163, produced by Lb. plantarum 163 was purified by salt precipitation, gel filtration, and reverse-phase high-performance liquid chromatography (RP-HPLC). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis of plantaricin 163 revealed the molecular weight to be 3553.2 Da. The complete amino acid sequence showed VFHAYSARGNYYGNCPANWPSCRNNYKSAGGK, and no similarity to known bacteriocins was found. Plantaricin 163 was highly thermostable (20 min, 121 °C), active in the presence of acidic pH (3-5), sensitive to protease, and exhibited broad-spectrum antimicrobial activity against LAB and other tested Gram-positive and Gram-negative bacteria. The results suggest that plantaricin 163 may be employed as a biopreservative in the food industry.

Antifungal activity and mechanism of fengycin in the presence and absence of commercial surfactin against Rhizopus stolonifer

The antifungal activity and mechanism of fengycin in the presence and absence of commercial surfactin against Rhizopus stolonifer were investigated. The MIC (minimal inhibitory concentration) of fengycin without commercial surfactin added was 0.4 mg/ml while the MIC of fengycin with commercial surfactin added was 2.0 mg/ml. Fengycin acted on cell membrane and cellular organs and inhibited DNA synthesis. The antifungal effect of fengycin was reduced after commercial surfactin was added. All these results suggest that the fungal cell membrane may be the primary target of fengycin action and commercial surfactin may reduce the antifungal activity of fengycin.

Degradation of triphenylmethane dyes using a temperature and pH stable spore laccase from a novel strain of Bacillus vallismortis.

The characterization of a spore laccase from Bacillus vallismortis fmb-103, isolated from textile industry disposal sites, is described. The activity was 6.5 U/g of dry spore with ABTS as the substrate. The enzyme was quite stable at high temperature. It retained more than 90% of its initial activity after 10h at 70 °C. The enzyme demonstrated broad pH stability in both acidic and alkaline conditions. There was almost no activity loss at pH 3 over an extended period of time, and the relative activity remained at 82% and 38% at pH 7 and pH 9 after 10 days. NaN(3), SDS, L-cysterine, Dithiothreitol, EDTA and NaCl inhibit the enzyme activity. Triphenylmethane dyes, including malachite green, brilliant green and aniline blue were efficiently degraded by the enzyme after 24h in combination with a mediator with efficiencies of 76.84%, 96.56% and 81.17%, respectively. The reusability of spore laccase for decolorization dyes was also examined.

Purification and characterization of a novel anticoagulant and fibrinolytic enzyme produced by endophytic bacterium Paenibacillus polymyxa EJS-3

INTRODUCTION Endophytes may become a new source of thrombolytic agents for thrombosis treatment. MATERIALS AND METHODS A novel fibrinolytic enzyme from Paenibacillus polymyxa EJS-3 (PPFE-I) was purified with ammonium sulfate precipitation, hydrophobic chromatography, ion exchange and gel filtration chromatography. The characterization of the enzyme was investigated by means of fibrinolysis plate, hydrolysis of fibrinogen and anticoagulant effect in vitro. RESULTS The fibrinolytic enzyme is purified to homogeneity with a purification of 14.5 fold and a recovery of 3.3%. The enzyme was shown to have a molecular mass of 63.3kDa by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The optimum temperature and pH value were 37°C and 7.5, respectively. Results from the fibrinolysis pattern showed that the enzyme rapidly hydrolyzed the Aα-chain of fibrinogen, followed by the Bβ-chains. It also hydrolyzed the γ-chains, but more slowly. It was activated by metal ions such as Zn(2+), Mg(2+), and Fe(2+), but inhibited by Ca(2+) and Cu(2+). Furthermore, PPFE-I activity was inhibited strongly by PMSF, and it was found to exhibit a higher specificity for the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-pNA for chymotrypsin, indicating that the enzyme is a chymotrypsin-like serine protease. Additionly, PPFE-I showed a significant anticoagulant effect in vitro. CONCLUSION The fibrinolytic enzyme PPFE-I from endophytic bacterium Paenibacillu polymyxa EJS-3 exhibits a profound fibrinolytic activity.

Isolation and Identification of an Endophytic Strain EJS-3 Producing Novel Fibrinolytic Enzymes

An endophytic strain EJS-3, which produces a novel fibrinolytic enzyme, was screened from root tissue of Stemona japonica (Blume) Miq, a chinese traditional medicine. This strain was identified as Paenibacillus polymyxa (DQ120522) by morphological, physiological, and biochemical tests and 16S rRNA gene sequence analysis. Two serine-type fibrinolytic enzymes with a relative molecular weight about 118 and 49 kDa, respectively, which are larger than known fibrinolytic enzymes, were found by the SDS–fibrin zymogram or by fibrin-inhibitor zymography gels. No work on P. polymyxa-producing fibrinolytic enzymes has been reported.