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In this paper, we demonstrate that, by adding a small amount of \CF4 (2\%) into a compressed-air planar dielectric barrier discharge (DBD), one can effectively inactivate a B. subtilis spore up to 50 mm in width in the postdischarge jet region after ten passes of exposure of plasma plume (equivalent plasma exposure time of 1 s) for treatment distance of up to 14 mm for the spore concentration in the range of 10^5-10^7 CFU/mL. A possible mechanism is proposed, i.e., the chemically active F atoms and \CFn\ ({n} = 1 - 3) are generated through the help of abundant excited nitrogen molecules in the postdischarge region. [ABSTRACT FROM PUBLISHER]

Tandem production of levan and ethanol by microbial fermentation using sucrose substrate was investigated. The tandem process involves fermentation of Bacillus subtilis(natto) Takahashi in a sucrose medium to produce levan, separation of the levan product from glucose by-product by ultrafiltration and fermentation of the glucose remnant from levan production by Zymomonas mobilisto produce ethanol. After cultivation of B. subtilis(natto) Takahashi for 48 h, 56.0 ± 0.6 g l−1of levan was produced in a medium containing 250 g l−1sucrose, which was 45 ± 0.5% yield on available fructose. After removing the cells, the fermentation broth was concentrated by ultrafiltration through a membrane of 5 kDa cutoff. The filtrate which contained 179 ± 3 g l−1of hexose was diluted, supplemented with yeast extract (5 g l−1), (NH4)2SO4(1 g l−1), MgSO4·7H2O (0.5 g l−1), KH2PO4(1 g l−1) and used for alcohol fermentation by Z. mobilis. Incubation of Z. mobilisin the medium containing glucose remnant at 30 °C, pH 5.5, 175 rpm for 120 h gave from 21.1 ± 0.3 to 26.5 ± 0.2 g l−1of bio-ethanol depending on the dilution. The tandem process developed in this study is an eco-friendly process in that the sucrose substrate was fully utilized without wasting any by-products in the process; in addition, two invaluable environmentally-friendly biomaterials (levan and ethanol) were produced. Furthermore, the amount of alcohol required for levan recovery could be reduced to a quarter of that generally used in the conventional precipitation. [ABSTRACT FROM AUTHOR]

Abstract: Biopolymer DYU500 produced from Bacillus subtilis DYU1 was found to have excellent flocculating ability. With the addition of 40mg-DYU500/L and 50mM CaCO3, the optimum temperature for flocculation performance of DYU500 was 30°C, giving the highest flocculating activity and rate of 13.5 and 97%, respectively. Analysis with Fourier transform infrared spectrophotometry (FT-IR), nuclear magnetic resonance spectrometry (NMR) and amino acid identification shows that the DYU500 biopolymer mainly possesses the structure of poly-glutamic acid (PGA). The average molecular weight of DYU500 was about (3.16–3.20)×106 Da as determined by gel permeation chromatography. The major components of biopolymer DYU500 were total sugars, uronic acids, proteins and polyamides (homopolymer of glutamic acid), accounting for a weight ratio of approximate 14.9, 2.7, 4.4 and 48.7% (w/w), respectively. The flocculating activity of DYU500 in the kaolin suspension was markedly stimulated by the addition of bivalent cations Ca2+ or Mg2+ in optimum concentration ranges of about 0.15–0.90 and 0.10–0.90mM, respectively. The synergistic effect of cations was most effective at a weak acidic or neutral pH (6.0–7.0). The flocculating activity of DYU500 linearly decreased with an increase in incubation temperature and the activity was completely lost when heating upon 120°C, arising from the destruction of the polyamides structure of DYU500. Moreover, mechanisms describing the flocculation process with DYU500 were proposed based on the experimental observations. [Copyright &y& Elsevier]

Abstract: The immobilization of B. subtilis natto Takahashi on alginate matrix was attempted for repeated production of levan. Factors that influence the stability of the immobilized-cell beads and the levan production in the process of fermentation were also investigated. The levan production and the stability of immobilized beads were greatly affected by the sucrose concentration, medium pH, metal ions and agitation speed. When the immobilized cells were cultivated in the optimal conditions, high levan production (70.6g/L) was obtained after 3 d of fermentation and no damaged beads were observed. In the repetitive cultivation, the supplement of organic nitrogen source and control of initial pH was critical for high levan production. Immobilized cells on alginate beads were reused in five successive reaction cycles (each cycle 72h) without any loss of biocatalytic activity and 9 cycles with 72% residual activity. [Copyright &y& Elsevier]