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Yield improvement of exopolysaccharides by screening of the Lactobacillus acidophilus ATCC and optimization of the fermentation and extraction conditions.

Liu Q, Huang X, Yang D, Si T, Pan S, Yang F - EXCLI J (2016)

Bottom Line: It was revealed that three parameters (Tween 80, dipotassium hydrogen phosphate and trisodium citrate) had significant influence (P < 0.05) on the EPS yield.In these conditions, the maximum EPS extraction yield was 1.48±0.23 g/L.The results indicated that the strain screening with high-yielding EPS was successful and the optimized fermentation and extraction conditions significantly enhanced EPS yield.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Engineering, Hubei University Zhixing College, Wuhan 430011, China; College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.

ABSTRACT
Exopolysacharides (EPS) produced by Lactobacillus acidophilus play an important role in food processing with its well-recognized antioxidant activity. In this study, a L. acidophilus mutant strain with high-yielding EPS (2.92±0.05 g/L) was screened by chemical mutation (0.2 % diethyl sulfate). Plackett-Burman (PB) design and response surface methodology (RSM) were applied to optimize the EPS fermentation parameters and central composite design (CCD) was used to optimize the EPS extraction parameters. A strain with high-yielding EPS was screened. It was revealed that three parameters (Tween 80, dipotassium hydrogen phosphate and trisodium citrate) had significant influence (P < 0.05) on the EPS yield. The optimal culture conditions for EPS production were: Tween 80 0.6 mL, dipotassium hydrogen phosphate 3.6 g and trisodium citrate 4.1 g (with culture volume of 1 L). In these conditions, the maximum EPS yield was 3.96±0.08 g/L. The optimal extraction conditions analyzed by CCD were: alcohol concentration 70 %, the ratio of material to liquid (M/L ratio) 1:3.6 and the extraction time 31 h. In these conditions, the maximum EPS extraction yield was 1.48±0.23 g/L. It was confirmed by the verification experiments that the EPS yield from L. acidophilus mutant strains reached 5.12±0.73 g/L under the optimized fermentation and extraction conditions, which was 3.8 times higher than that of the control (1.05±0.06 g/L). The results indicated that the strain screening with high-yielding EPS was successful and the optimized fermentation and extraction conditions significantly enhanced EPS yield. It was efficient and industrially promising.

No MeSH data available.


Related in: MedlinePlus

Significance of 16 variables on EPS yields from activated L. acidophilus ATCC. (a) Represented the pareto chat rationalizing the effect of each variable on EPS yield. The standard effects of 16 variables were calculated by MINITAB 16. The average standard effect was 2.07. (b) Represented the main effect of variables on EPS yield. The slope of each variable was steeper; the influence of each variable was greater.
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Figure 2: Significance of 16 variables on EPS yields from activated L. acidophilus ATCC. (a) Represented the pareto chat rationalizing the effect of each variable on EPS yield. The standard effects of 16 variables were calculated by MINITAB 16. The average standard effect was 2.07. (b) Represented the main effect of variables on EPS yield. The slope of each variable was steeper; the influence of each variable was greater.

Mentions: The design matrix was selected to screen significant variables for the fermentation process of EPS and the corresponding results were shown in Table 1(Tab. 1). The coefficient of determination (R2) of the model was 0.990, which indicated that the model could explain 99.0 % of the data variation. The statistically significant effects of the variables were presented in Figure 2a(Fig. 2). Among the 16 fermentation variables, 7 variables (Dipotassium hydrogen phosphate, Tween 80, Trisodium citrate, Glucose, pH, Rotaton speed, Yeast extract) had statistically significant effect on the EPS yield (P < 0.05, significant at 5 % level) and the results were obtained from regression analysis. In the 16 variables, 6 variables had a positive influence on the EPS yield, while 6 variables had a negative effect on the EPS yield (Figure 2b(Fig. 2)). Among the 16 variables, Dipotassium hydrogen phosphate with a P value of 0.003 was identified to be the most significant factor, followed by Tween 80 (P = 0.004) and Trisodium citrate (P = 0.008). The lower P values indicated the more significant factors on the EPS yield. In the 3 factors, Tween 80 exerted a negative effect on the EPS yield, whereas the other two factors showed a positive influence on the EPS yield. Most bacteria can produce EPS under certain conditions, but the quantities and the composition of EPS are strain dependence and affected by the nutritional and environmental conditions. So it is possible to increase the polymer production by manipulating the culture conditions (Looijesteijn and Hugenholtz, 1999[28]; Xu et al., 2010[50]). The Plackett-Burman experiments can screen out main factors from a large number of process variables quickly, which are quite useful in preliminary studies and its principal objective is to select variables and their levels for further optimization processes (Reddy et al., 2008[35]). In the previous articles, 3 to 5 culture factors with most significant effect are selected (Chen et al., 2005[8]; Yasser et al., 2005[52]) or the factors with confidence interval from 80 % to 85 % are selected with Placket-Burman experiments for further optimization (Pujari and Chandra, 2000[34]; Xiong et al., 2004[49]). In the present study, 16 variables were selected to optimize polysaccharide fermentation conditions with Placket-Burman experiments and the three chosen variables with confidence interval above 95 % indicated that the further optimization would be more accurate. In the previous studies, medium components, inoculum size, fermentation time and temperature are determined as the significant factors in fermentation process by analyzing with PB experiments (Reddy et al., 2008[35]; Xu et al., 2010[50]). The results of this study revealed that the main impact factors for EPS produced by L. acidophilus were medium components (Trisodium citrate, Dipotassium hydrogen phosphate and Tween 80).


Yield improvement of exopolysaccharides by screening of the Lactobacillus acidophilus ATCC and optimization of the fermentation and extraction conditions.

Liu Q, Huang X, Yang D, Si T, Pan S, Yang F - EXCLI J (2016)

Significance of 16 variables on EPS yields from activated L. acidophilus ATCC. (a) Represented the pareto chat rationalizing the effect of each variable on EPS yield. The standard effects of 16 variables were calculated by MINITAB 16. The average standard effect was 2.07. (b) Represented the main effect of variables on EPS yield. The slope of each variable was steeper; the influence of each variable was greater.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834753&req=5

Figure 2: Significance of 16 variables on EPS yields from activated L. acidophilus ATCC. (a) Represented the pareto chat rationalizing the effect of each variable on EPS yield. The standard effects of 16 variables were calculated by MINITAB 16. The average standard effect was 2.07. (b) Represented the main effect of variables on EPS yield. The slope of each variable was steeper; the influence of each variable was greater.
Mentions: The design matrix was selected to screen significant variables for the fermentation process of EPS and the corresponding results were shown in Table 1(Tab. 1). The coefficient of determination (R2) of the model was 0.990, which indicated that the model could explain 99.0 % of the data variation. The statistically significant effects of the variables were presented in Figure 2a(Fig. 2). Among the 16 fermentation variables, 7 variables (Dipotassium hydrogen phosphate, Tween 80, Trisodium citrate, Glucose, pH, Rotaton speed, Yeast extract) had statistically significant effect on the EPS yield (P < 0.05, significant at 5 % level) and the results were obtained from regression analysis. In the 16 variables, 6 variables had a positive influence on the EPS yield, while 6 variables had a negative effect on the EPS yield (Figure 2b(Fig. 2)). Among the 16 variables, Dipotassium hydrogen phosphate with a P value of 0.003 was identified to be the most significant factor, followed by Tween 80 (P = 0.004) and Trisodium citrate (P = 0.008). The lower P values indicated the more significant factors on the EPS yield. In the 3 factors, Tween 80 exerted a negative effect on the EPS yield, whereas the other two factors showed a positive influence on the EPS yield. Most bacteria can produce EPS under certain conditions, but the quantities and the composition of EPS are strain dependence and affected by the nutritional and environmental conditions. So it is possible to increase the polymer production by manipulating the culture conditions (Looijesteijn and Hugenholtz, 1999[28]; Xu et al., 2010[50]). The Plackett-Burman experiments can screen out main factors from a large number of process variables quickly, which are quite useful in preliminary studies and its principal objective is to select variables and their levels for further optimization processes (Reddy et al., 2008[35]). In the previous articles, 3 to 5 culture factors with most significant effect are selected (Chen et al., 2005[8]; Yasser et al., 2005[52]) or the factors with confidence interval from 80 % to 85 % are selected with Placket-Burman experiments for further optimization (Pujari and Chandra, 2000[34]; Xiong et al., 2004[49]). In the present study, 16 variables were selected to optimize polysaccharide fermentation conditions with Placket-Burman experiments and the three chosen variables with confidence interval above 95 % indicated that the further optimization would be more accurate. In the previous studies, medium components, inoculum size, fermentation time and temperature are determined as the significant factors in fermentation process by analyzing with PB experiments (Reddy et al., 2008[35]; Xu et al., 2010[50]). The results of this study revealed that the main impact factors for EPS produced by L. acidophilus were medium components (Trisodium citrate, Dipotassium hydrogen phosphate and Tween 80).

Bottom Line: It was revealed that three parameters (Tween 80, dipotassium hydrogen phosphate and trisodium citrate) had significant influence (P < 0.05) on the EPS yield.In these conditions, the maximum EPS extraction yield was 1.48±0.23 g/L.The results indicated that the strain screening with high-yielding EPS was successful and the optimized fermentation and extraction conditions significantly enhanced EPS yield.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Engineering, Hubei University Zhixing College, Wuhan 430011, China; College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.

ABSTRACT
Exopolysacharides (EPS) produced by Lactobacillus acidophilus play an important role in food processing with its well-recognized antioxidant activity. In this study, a L. acidophilus mutant strain with high-yielding EPS (2.92±0.05 g/L) was screened by chemical mutation (0.2 % diethyl sulfate). Plackett-Burman (PB) design and response surface methodology (RSM) were applied to optimize the EPS fermentation parameters and central composite design (CCD) was used to optimize the EPS extraction parameters. A strain with high-yielding EPS was screened. It was revealed that three parameters (Tween 80, dipotassium hydrogen phosphate and trisodium citrate) had significant influence (P < 0.05) on the EPS yield. The optimal culture conditions for EPS production were: Tween 80 0.6 mL, dipotassium hydrogen phosphate 3.6 g and trisodium citrate 4.1 g (with culture volume of 1 L). In these conditions, the maximum EPS yield was 3.96±0.08 g/L. The optimal extraction conditions analyzed by CCD were: alcohol concentration 70 %, the ratio of material to liquid (M/L ratio) 1:3.6 and the extraction time 31 h. In these conditions, the maximum EPS extraction yield was 1.48±0.23 g/L. It was confirmed by the verification experiments that the EPS yield from L. acidophilus mutant strains reached 5.12±0.73 g/L under the optimized fermentation and extraction conditions, which was 3.8 times higher than that of the control (1.05±0.06 g/L). The results indicated that the strain screening with high-yielding EPS was successful and the optimized fermentation and extraction conditions significantly enhanced EPS yield. It was efficient and industrially promising.

No MeSH data available.


Related in: MedlinePlus