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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

Contour plot of EPS extraction for the effect of cross-interaction among alcohol concentration, M/L ratio and extraction time. a: Cross-interaction between M/L ratio and concentration of ethanol. Hold value: extraction time 24 h. b: Cross-interaction between extraction time and M/L ratio. Hold value: alcohol concentration 70 %. c: Cross-interaction between extraction time and alcohol concentration. Hold value: M/L ratio 1:3.
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Figure 4: Contour plot of EPS extraction for the effect of cross-interaction among alcohol concentration, M/L ratio and extraction time. a: Cross-interaction between M/L ratio and concentration of ethanol. Hold value: extraction time 24 h. b: Cross-interaction between extraction time and M/L ratio. Hold value: alcohol concentration 70 %. c: Cross-interaction between extraction time and alcohol concentration. Hold value: M/L ratio 1:3.

Mentions: Regression analysis showed that alcohol concentration and M/L ratio had a significant positive linear effect on the extraction yield of EPS (P < 0.01) and extraction time had a negative effect on the extraction yield of EPS. The M/L ratio had the highest impact on the extraction yield (the coefficient is 0.985) and the extraction time had the lowest impact (the coefficient is 0.069). The quadratic and interactive effects were also significant. The interactive effects of various factors on extraction ratio of EPS were presented in Figure 4(Fig. 4). The elliptical contour plot implied a significant interaction between the two variables with the rest variable at middle level. When extract time kept 24 h, the extraction ratio of EPS would increase firstly and then decrease with the ratio of M/L and concentration of ethanol increasing. Polysaccharide is not soluble in ethanol; therefore, more polysaccharide can be precipitated by increasing the concentration of ethanol moderately. On the other hand, because the ratio of M/L means the ratio of the supernatants to ethanol, it has the corresponding effect on the extraction ratio of EPS with the ethanol concentration. When the concentration of ethanol and ratio of M/L were 72.5 % and 1:3.5 respectively, the extraction ratio of EPS was the highest (Figure 4a(Fig. 4)). When the concentration of ethanol kept 70 %, the extraction ratio of EPS would increase with the ratio of M/L increasing, which further proved that the ethanol content has a significant effect on polysaccharide extraction. While the extraction ratio decreased firstly and then increase with the extraction time increasing. When the extract time and ratio of M/L were 30 h and 1:3.5 respectively, the extraction ratio of EPS was the highest (Figure 4b(Fig. 4)). When the ratio of M/L kept 1:3, the extraction ratio of EPS would increase firstly and then decrease with the concentration of ethanol increasing. However, it would firstly decrease and then increase with the extract time increasing. When the concentration of ethanol and extract time was 70 % and 30 h, the extraction ratio of EPS was highest (Figure 4c(Fig. 4)). The optimum levels of each variable were determined to be as follows: the alcohol concentration was 70 %, M/L ratio was 1:3.6, and the extraction time was 31 h. At these optimum levels, EPS extraction yield of 1.48±0.23 g/L was obtained, which had no significant difference with the predicted value (1.56 g/L) (P > 0.05). It was higher than that of the control (1.05±0.06 g/L) significantly (P < 0.05). Although there were many articles about EPS extraction of microorganism (Chen et al., 2012[9]; Gan et al., 2011[13]), while in the present study, the extraction condition was firstly optimized with CCD design. The EPS extraction yield was promoted by 48.57 % under the optimized extraction conditions.


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)

Contour plot of EPS extraction for the effect of cross-interaction among alcohol concentration, M/L ratio and extraction time. a: Cross-interaction between M/L ratio and concentration of ethanol. Hold value: extraction time 24 h. b: Cross-interaction between extraction time and M/L ratio. Hold value: alcohol concentration 70 %. c: Cross-interaction between extraction time and alcohol concentration. Hold value: M/L ratio 1:3.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Contour plot of EPS extraction for the effect of cross-interaction among alcohol concentration, M/L ratio and extraction time. a: Cross-interaction between M/L ratio and concentration of ethanol. Hold value: extraction time 24 h. b: Cross-interaction between extraction time and M/L ratio. Hold value: alcohol concentration 70 %. c: Cross-interaction between extraction time and alcohol concentration. Hold value: M/L ratio 1:3.
Mentions: Regression analysis showed that alcohol concentration and M/L ratio had a significant positive linear effect on the extraction yield of EPS (P < 0.01) and extraction time had a negative effect on the extraction yield of EPS. The M/L ratio had the highest impact on the extraction yield (the coefficient is 0.985) and the extraction time had the lowest impact (the coefficient is 0.069). The quadratic and interactive effects were also significant. The interactive effects of various factors on extraction ratio of EPS were presented in Figure 4(Fig. 4). The elliptical contour plot implied a significant interaction between the two variables with the rest variable at middle level. When extract time kept 24 h, the extraction ratio of EPS would increase firstly and then decrease with the ratio of M/L and concentration of ethanol increasing. Polysaccharide is not soluble in ethanol; therefore, more polysaccharide can be precipitated by increasing the concentration of ethanol moderately. On the other hand, because the ratio of M/L means the ratio of the supernatants to ethanol, it has the corresponding effect on the extraction ratio of EPS with the ethanol concentration. When the concentration of ethanol and ratio of M/L were 72.5 % and 1:3.5 respectively, the extraction ratio of EPS was the highest (Figure 4a(Fig. 4)). When the concentration of ethanol kept 70 %, the extraction ratio of EPS would increase with the ratio of M/L increasing, which further proved that the ethanol content has a significant effect on polysaccharide extraction. While the extraction ratio decreased firstly and then increase with the extraction time increasing. When the extract time and ratio of M/L were 30 h and 1:3.5 respectively, the extraction ratio of EPS was the highest (Figure 4b(Fig. 4)). When the ratio of M/L kept 1:3, the extraction ratio of EPS would increase firstly and then decrease with the concentration of ethanol increasing. However, it would firstly decrease and then increase with the extract time increasing. When the concentration of ethanol and extract time was 70 % and 30 h, the extraction ratio of EPS was highest (Figure 4c(Fig. 4)). The optimum levels of each variable were determined to be as follows: the alcohol concentration was 70 %, M/L ratio was 1:3.6, and the extraction time was 31 h. At these optimum levels, EPS extraction yield of 1.48±0.23 g/L was obtained, which had no significant difference with the predicted value (1.56 g/L) (P > 0.05). It was higher than that of the control (1.05±0.06 g/L) significantly (P < 0.05). Although there were many articles about EPS extraction of microorganism (Chen et al., 2012[9]; Gan et al., 2011[13]), while in the present study, the extraction condition was firstly optimized with CCD design. The EPS extraction yield was promoted by 48.57 % under the optimized extraction conditions.

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