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Statistical optimization of process variables for antibiotic activity of Xenorhabdus bovienii.

Fang XL, Han LR, Cao XQ, Zhu MX, Zhang X, Wang YH - PLoS ONE (2012)

Bottom Line: A 2(5-1) factorial central composite design was chosen to determine the combined effects of the five variables, and to design a minimum number of experiments.The experimental and predicted antibiotic activity of X. bovienii YL002 was in close agreement.After optimization, the antibiotic activity was improved by 23.02% as compared with that of unoptimized conditions.

View Article: PubMed Central - PubMed

Affiliation: Research and Development Center of Biorational Pesticides, Northwest A & F University, Yangling, Shaanxi, People's Republic of China.

ABSTRACT
The production of secondary metabolites with antibiotic properties is a common characteristic to entomopathogenic bacteria Xenorhabdus spp. These metabolites not only have diverse chemical structures but also have a wide range of bioactivities of medicinal and agricultural interests. Culture variables are critical to the production of secondary metabolites of microorganisms. Manipulating culture process variables can promote secondary metabolite biosynthesis and thus facilitate the discovery of novel natural products. This work was conducted to evaluate the effects of five process variables (initial pH, medium volume, rotary speed, temperature, and inoculation volume) on the antibiotic production of Xenorhabdus bovienii YL002 using response surface methodology. A 2(5-1) factorial central composite design was chosen to determine the combined effects of the five variables, and to design a minimum number of experiments. The experimental and predicted antibiotic activity of X. bovienii YL002 was in close agreement. Statistical analysis of the results showed that initial pH, medium volume, rotary speed and temperature had a significant effect (P<0.05) on the antibiotic production of X. bovienii YL002 at their individual level; medium volume and rotary speed showed a significant effect at a combined level and was most significant at an individual level. The maximum antibiotic activity (287.5 U/mL) was achieved at the initial pH of 8.24, medium volume of 54 mL in 250 mL flask, rotary speed of 208 rpm, temperature of 32.0°C and inoculation volume of 13.8%. After optimization, the antibiotic activity was improved by 23.02% as compared with that of unoptimized conditions.

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Pareto chart of t-values for coefficients.
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pone-0038421-g001: Pareto chart of t-values for coefficients.

Mentions: Quadratic response surface regression designs are a hybrid type of design with characteristics of both polynomial regression designs and fractional factorial regression designs, which contain all the same effects of polynomial regression designs to degree 2 and additionally the 2-way interaction effects of the predictor variables. Each effect could be estimated independently due to the orthogonal design. The ANOVA result was shown in Table 3. The linear term of X1, X2, X3 and X4 were significant at P<0.05 level. Among the linear terms, the main effects of medium volume and rotary speed on the antibiotic activity were most significant as was evident from their respective P-values (PX2 = 0.000097 and PX3 = 0.0000). Temperature also had significant effect on the antibiotic activity at the linear term (PX4 = 025843). Partial eta squared was used as a measure of effect size. Rotary speed had highest effect on the antibiotic production as given by highest linear partial eta squared (0.860558), followed by medium volume (0.647835), pH (0.377276) and temperature (0.289636). The Pareto chart showed each of the estimated effects, interactions and the standard deviation of each of the effects which measures their sampling error (Fig. 1). In the experimental design the Pareto chart is a Frequency Histogram that shows the amount of effect of each factor has on the response in decreasing order, and often, a line going across the columns indicates how large an effect has to be (i.e., how long a column must be) to be statistically significant. Quadratic term of X12, X32 and X42 (pH, rotary speed and temperature) were significant P<0.05. The result also indicated that pH, rotary speed and temperature could act as limiting factors, and small variations in their values will considerably alter either growth rate or product formation rate or both. Interactive terms of X1X2, X1X 4 and X2X3 were also significant at P<0.05. The interaction between medium volume and rotary speed had significant effect on antibiotic production (PX2X3<0.007731). These results suggested that medium volume and rotary speed had a direct relationship with antibiotic activity under this condition.


Statistical optimization of process variables for antibiotic activity of Xenorhabdus bovienii.

Fang XL, Han LR, Cao XQ, Zhu MX, Zhang X, Wang YH - PLoS ONE (2012)

Pareto chart of t-values for coefficients.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368850&req=5

pone-0038421-g001: Pareto chart of t-values for coefficients.
Mentions: Quadratic response surface regression designs are a hybrid type of design with characteristics of both polynomial regression designs and fractional factorial regression designs, which contain all the same effects of polynomial regression designs to degree 2 and additionally the 2-way interaction effects of the predictor variables. Each effect could be estimated independently due to the orthogonal design. The ANOVA result was shown in Table 3. The linear term of X1, X2, X3 and X4 were significant at P<0.05 level. Among the linear terms, the main effects of medium volume and rotary speed on the antibiotic activity were most significant as was evident from their respective P-values (PX2 = 0.000097 and PX3 = 0.0000). Temperature also had significant effect on the antibiotic activity at the linear term (PX4 = 025843). Partial eta squared was used as a measure of effect size. Rotary speed had highest effect on the antibiotic production as given by highest linear partial eta squared (0.860558), followed by medium volume (0.647835), pH (0.377276) and temperature (0.289636). The Pareto chart showed each of the estimated effects, interactions and the standard deviation of each of the effects which measures their sampling error (Fig. 1). In the experimental design the Pareto chart is a Frequency Histogram that shows the amount of effect of each factor has on the response in decreasing order, and often, a line going across the columns indicates how large an effect has to be (i.e., how long a column must be) to be statistically significant. Quadratic term of X12, X32 and X42 (pH, rotary speed and temperature) were significant P<0.05. The result also indicated that pH, rotary speed and temperature could act as limiting factors, and small variations in their values will considerably alter either growth rate or product formation rate or both. Interactive terms of X1X2, X1X 4 and X2X3 were also significant at P<0.05. The interaction between medium volume and rotary speed had significant effect on antibiotic production (PX2X3<0.007731). These results suggested that medium volume and rotary speed had a direct relationship with antibiotic activity under this condition.

Bottom Line: A 2(5-1) factorial central composite design was chosen to determine the combined effects of the five variables, and to design a minimum number of experiments.The experimental and predicted antibiotic activity of X. bovienii YL002 was in close agreement.After optimization, the antibiotic activity was improved by 23.02% as compared with that of unoptimized conditions.

View Article: PubMed Central - PubMed

Affiliation: Research and Development Center of Biorational Pesticides, Northwest A & F University, Yangling, Shaanxi, People's Republic of China.

ABSTRACT
The production of secondary metabolites with antibiotic properties is a common characteristic to entomopathogenic bacteria Xenorhabdus spp. These metabolites not only have diverse chemical structures but also have a wide range of bioactivities of medicinal and agricultural interests. Culture variables are critical to the production of secondary metabolites of microorganisms. Manipulating culture process variables can promote secondary metabolite biosynthesis and thus facilitate the discovery of novel natural products. This work was conducted to evaluate the effects of five process variables (initial pH, medium volume, rotary speed, temperature, and inoculation volume) on the antibiotic production of Xenorhabdus bovienii YL002 using response surface methodology. A 2(5-1) factorial central composite design was chosen to determine the combined effects of the five variables, and to design a minimum number of experiments. The experimental and predicted antibiotic activity of X. bovienii YL002 was in close agreement. Statistical analysis of the results showed that initial pH, medium volume, rotary speed and temperature had a significant effect (P<0.05) on the antibiotic production of X. bovienii YL002 at their individual level; medium volume and rotary speed showed a significant effect at a combined level and was most significant at an individual level. The maximum antibiotic activity (287.5 U/mL) was achieved at the initial pH of 8.24, medium volume of 54 mL in 250 mL flask, rotary speed of 208 rpm, temperature of 32.0°C and inoculation volume of 13.8%. After optimization, the antibiotic activity was improved by 23.02% as compared with that of unoptimized conditions.

Show MeSH
Related in: MedlinePlus