Influence of agitation and aeration on growth and antibiotic production by Xenorhabdus nematophila. World

World Journal of Microbiology and Biotechnology (Impact Factor: 1.35). 01/2007; 23(2):221-227. DOI: 10.1007/s11274-006-9217-2

ABSTRACT The effect of agitation and aeration on the growth and antibiotic production by Xenorhabdus nematophila YL001 grown in batch cultures were investigated. Efficiency of aeration and agitation was evaluated through the oxygen mass
transfer coefficient (K
a). With increase in K
a, the biomass and antibiotic activity increased. Activity units of antibiotic and dry cell weight were increased to 232Uml−1 and 19.58gl−1, respectively, productivity in cell and antibiotic was up more than 30% when K
a increased from 115.9h−1 to 185.7h−1. During the exponential growth phase, DO concentration was zero, the oxygen supply was not sufficient. So, based on process
analysis, a three-stage oxygen supply control strategy was used to improved the DO concentration above 30% by controlling
the agitation speed and aeration rate. The dry cell weight and activity units of antibiotic were further increased to 24.22gl−1 and 249Uml−1, and were improved by 24.0% and 7.0%, compared with fermentation at a constant agitation speed and a constant aeration rate
(300revmin−1, 2.5lmin−1).

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    • "overcome the insect immune system, kill the insect and inhibit the growth of various fungal and bacterial competitors (Chen et al., 1996). By so doing, the bacterial symbionts are believed to prevent putrefaction of the insect cadaver and establish conditions that favor the development of both the nematode and bacterial symbionts (Wang and Zhang, 2007). Xenorhabdus and Photorhabdus secrete a wide variety of substance into the culture medium including toxins, lipases, proteases, antibiotics and lipopolysaccharides (Caldas et al., 2002; Richards et al., 2008; Hu and Webster, 2000). "
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    ABSTRACT: In the present study, we isolated 23 strains of symbiotic bacteria from 23 entomopathogenic nematodes strains gathered in different vegetation from different regions of China. The antibiotic activities of all these bacteria strains isolated were evaluated in the laboratory. All the bacteria effectively inhibited seven kinds of plant pathogenic fungi (Bipolaris sorokinianum, Fusarium graminearum, Fusarium moniliforme, Cordana musae (zimm.) Hohn, Colletotrichum gloeosporiodies, Alternaria solani and Alternaria alternata (Fries) Keissler) cultured on agar plates. Among these strains, strain SY5 was the most effective symbiotic bacteria strain, which was further selected as the highly virulent bacteria for the adversity resistance study. The adversity resistance showed that the stability of the antibiotic activity against different plant pathogenic fungi was different. The antibiotic activity against A. solani was the most stable and the inhibiting rate was not affected by treatment in a 50°C water bath for 60 min and in 100°C for 10 min, ultraviolet light exposure for 120 min and storing at room temperature for 90 days.
    African journal of microbiology research 11/2011; 5(28). DOI:10.5897/AJMR11.758 · 0.54 Impact Factor
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    • "However, most of the studies on the antibiotic production are confined to shake flasks, where the quantification of dissolved oxygen (DO) level is rather difficult. There are some reports on the effect of agitation and aeration rates on the production of antibiotic in a bioreactor (Wang and Zhang, 2007). However, these results did not include the effect of quantitative dissolved 0960-8524/$ -see front matter Ó 2010 Elsevier Ltd. "
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    ABSTRACT: To evaluate the effects of dissolved oxygen (DO) control strategy on cell growth and the production of antibiotic (cyclo(2-Me-BABA-Gly)) by Xenorhabdus nematophila. The effects of different agitation speeds and DO concentrations on cell growth and antibiotic activity of X. nematophila YL001 were examined. Experiments showed that higher agitation speeds and DO concentrations at earlier fermentation stage were favorable for cell growth and antibiotic production. At mid- and later-stage, properly decreasing DO concentration can strengthen cell growth and antibiotic production. Based on the kinetic information about the effects of agitation speeds and DO concentrations on the fermentation, the two-stage DO control strategy in which DO concentration was controlled to 70% in the first 18 h, and then switched to 50% after 18 h, was established to improve the biomass and antibiotic activity. By applying this DO-shift strategy in X. nematophila YL001 fermentation, maximal antibiotic activity and biomass reached 252.0+/-6.10 U/mL and 30.04+/-2.50 g/L, respectively, thus was 18.99% and 15.36% more than in the cultures at constantly 50% DO.
    Bioresource Technology 10/2010; 101(19):7529-36. DOI:10.1016/j.biortech.2010.04.070 · 5.04 Impact Factor
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    • "Such trends have been reported earlier for antibiotic production by Xenorhabdus sp. (Wang and Zhang 2007). Moreover, the STR adapted with a baffle was relatively unfavourable for the high yield of spore production (data not shown). "
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    ABSTRACT: To maximize spore production by Bacillus amyloliquefaciens B128, and its antagonism to the fungal pathogen Botrytis elliptica B061. In the 5-l stirred-tank bioreactor (STR), with the 0.5 vvm aeration rate, an agitation rate of 200 rev min(-1) significantly enhanced the spore yield compared to the same in 300 rev min(-1) cultivations. In a 20-l airlift bioreactor (ALR) the maximal spore production was further increased with a controlled aeration rate of 2.5 vvm operated in a 24-mesh net-draft tube mode, and no pH control cultivation. This spore yield in the 20-l ALR was five- and eightfold higher; in addition the cultivation period was 19 h shorter, compared to that obtained from shaker flask and in the 5-l STR cultivations respectively. Although culture conditions are still to be optimized, by using an ALR with net-draft tube, a scaling up from shaker flasks and STR to ALR of spore production by the strain B128 is technically feasible. The spore yields obtained using bioreactors were much higher than those previously reported. The freshly produced spore preparations from the B128 strain significantly antagonized the grey mould pathogen B. elliptica.
    Journal of Applied Microbiology 06/2008; 104(5):1275-82. DOI:10.1111/j.1365-2672.2007.03683.x · 2.39 Impact Factor
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