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

World Journal of Microbiology and Biotechnology (Impact Factor: 1.78). 01/2007; 23(2):221-227. DOI: 10.1007/s11274-006-9217-2


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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    • "But in other cases, the effect of increasing the oxygen transfer rate can significantly reduce the cellular yield, as reported for Bacillus licheniformis (8) or, to the contrary, it can stimulate cellular yield of Xenorhabdus nematophila (25). However, in cultures of microaerophilic Campylobacter jejuni and Pseudomonas aeruginosa PA01 dissolved oxygen (D.O) between 3 and 15% was optimal for growth, but above this value it had a negative effect on cellular growth (20, 22, 24). "
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    ABSTRACT: This study examined the effect of dissolved oxygen concentration on the production of biomass and metabolites with antimicrobial activity of Pseudoalteromonas sp cultured at 0, 150, 250, or 450 revolutions per minute (rev. min-1). Dissolved oxygen (D.O) was monitored during the fermentation process, biomass was quantified by dry weight, and antimicrobial activity was assessed using the disk diffusion method. The bacterium Pseudoalteromonas reached similar concentration of biomass under all experimental agitation conditions, whereas antimicrobial activity was detected at 0 and 150 rev. min-1 registering 0% and 12% of D.O respectively corresponding to microaerophilic conditions. Antibiotic activity was severely diminished when D.O was above 20% of saturation; this corresponded to 250 or 450 rev. min-1. SDS-PAGE electrophoresis revealed a protein with a molecular weight of approximately 80 kilodaltons (kDa) with antimicrobial activity. Pseudoalteromonas is capable of growing under oxic and microaerophilic conditions but the metabolites with antimicrobial activity are induced under microaerophilic conditions. The current opinion is that Pseudoalteromonas are aerobic organisms; we provide additional information on the amount of dissolved oxygen during the fermentation process and its effect on antimicrobial activity.
    Full-text · Article · Jul 2012 · Brazilian Journal of Microbiology
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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.
    Full-text · Article · Nov 2011 · African journal of microbiology research
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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.
    Full-text · Article · Oct 2010 · Bioresource Technology
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