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Kinetic study of batch and fed-batch enzymatic saccharification of pretreated substrate and subsequent fermentation to ethanol.

Gupta R, Kumar S, Gomes J, Kuhad RC - Biotechnol Biofuels (2012)

Bottom Line: Under batch mode, the actual sugar concentration values at 20% initial substrate consistency were found deviated from the predicted values and the maximum sugar concentration obtained was 80.78 g/L.Furthermore, model simulations showed that higher insoluble solids in the feed resulted in both smaller reactor volume and shorter residence time.Restricting the process to suitable kinetic regimes could result in higher conversion rates.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lignocellulose Biotechnology Laboratory, Department of Microbiology, University of Delhi South Campus, New Delhi 110021, India. kuhad85@gmail.com.

ABSTRACT

Background: Enzymatic hydrolysis, the rate limiting step in the process development for biofuel, is always hampered by its low sugar concentration. High solid enzymatic saccharification could solve this problem but has several other drawbacks such as low rate of reaction. In the present study we have attempted to enhance the concentration of sugars in enzymatic hydrolysate of delignified Prosopis juliflora, using a fed-batch enzymatic hydrolysis approach.

Results: The enzymatic hydrolysis was carried out at elevated solid loading up to 20% (w/v) and a comparison kinetics of batch and fed-batch enzymatic hydrolysis was carried out using kinetic regimes. Under batch mode, the actual sugar concentration values at 20% initial substrate consistency were found deviated from the predicted values and the maximum sugar concentration obtained was 80.78 g/L. Fed-batch strategy was implemented to enhance the final sugar concentration to 127 g/L. The batch and fed-batch enzymatic hydrolysates were fermented with Saccharomyces cerevisiae and ethanol production of 34.78 g/L and 52.83 g/L, respectively, were achieved. Furthermore, model simulations showed that higher insoluble solids in the feed resulted in both smaller reactor volume and shorter residence time.

Conclusion: Fed-batch enzymatic hydrolysis is an efficient procedure for enhancing the sugar concentration in the hydrolysate. Restricting the process to suitable kinetic regimes could result in higher conversion rates.

No MeSH data available.


Plots between the actual and the predicted values of glucose concentration released during the enzymatic hydrolysis of delignified lignocellulosic biomass at 5% (A), 10% (B), 15% (C) and 20% (D) initial substrate consistencies.
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Figure 2: Plots between the actual and the predicted values of glucose concentration released during the enzymatic hydrolysis of delignified lignocellulosic biomass at 5% (A), 10% (B), 15% (C) and 20% (D) initial substrate consistencies.

Mentions: The maximum rate constant (k1 = 0.0421 h-1) was obtained when the hydrolysis was carried out with 5% initial substrate concentration. The rate constants ki were then validated using the glucose concentration measurements obtained during the hydrolysis experiments. The root mean square error (RMSE) values between the predicted and the experimental values for enzymatic saccharification carried out at 5, 10, 15 and 20% initial substrate consistency were 0.997, 0.779, 1.843 and 1.995, respectively (Figure 2 a-d). The results also indicated that the maximum deviation of the experimental data from the model prediction was observed when the enzymatic saccharification was carried out at 20% initial substrate consistency. Moreover, the experimental values also depicted that the sugar concentration increased significantly only upto 15% substrate consistency and declined thereafter at 20% substrate level (Figure 2 a-d). The maximum sugar concentration obtained at each substrate concentration were 41.10 g/L (S1,0 = 5%), 72.47 g/L (S2,0 = 10%), 90.07 g/L (S3,0 = 15%) and 80.05 g/L (S4,0 = 20%) (see Figure 2 a-d).


Kinetic study of batch and fed-batch enzymatic saccharification of pretreated substrate and subsequent fermentation to ethanol.

Gupta R, Kumar S, Gomes J, Kuhad RC - Biotechnol Biofuels (2012)

Plots between the actual and the predicted values of glucose concentration released during the enzymatic hydrolysis of delignified lignocellulosic biomass at 5% (A), 10% (B), 15% (C) and 20% (D) initial substrate consistencies.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3369211&req=5

Figure 2: Plots between the actual and the predicted values of glucose concentration released during the enzymatic hydrolysis of delignified lignocellulosic biomass at 5% (A), 10% (B), 15% (C) and 20% (D) initial substrate consistencies.
Mentions: The maximum rate constant (k1 = 0.0421 h-1) was obtained when the hydrolysis was carried out with 5% initial substrate concentration. The rate constants ki were then validated using the glucose concentration measurements obtained during the hydrolysis experiments. The root mean square error (RMSE) values between the predicted and the experimental values for enzymatic saccharification carried out at 5, 10, 15 and 20% initial substrate consistency were 0.997, 0.779, 1.843 and 1.995, respectively (Figure 2 a-d). The results also indicated that the maximum deviation of the experimental data from the model prediction was observed when the enzymatic saccharification was carried out at 20% initial substrate consistency. Moreover, the experimental values also depicted that the sugar concentration increased significantly only upto 15% substrate consistency and declined thereafter at 20% substrate level (Figure 2 a-d). The maximum sugar concentration obtained at each substrate concentration were 41.10 g/L (S1,0 = 5%), 72.47 g/L (S2,0 = 10%), 90.07 g/L (S3,0 = 15%) and 80.05 g/L (S4,0 = 20%) (see Figure 2 a-d).

Bottom Line: Under batch mode, the actual sugar concentration values at 20% initial substrate consistency were found deviated from the predicted values and the maximum sugar concentration obtained was 80.78 g/L.Furthermore, model simulations showed that higher insoluble solids in the feed resulted in both smaller reactor volume and shorter residence time.Restricting the process to suitable kinetic regimes could result in higher conversion rates.

View Article: PubMed Central - HTML - PubMed

Affiliation: Lignocellulose Biotechnology Laboratory, Department of Microbiology, University of Delhi South Campus, New Delhi 110021, India. kuhad85@gmail.com.

ABSTRACT

Background: Enzymatic hydrolysis, the rate limiting step in the process development for biofuel, is always hampered by its low sugar concentration. High solid enzymatic saccharification could solve this problem but has several other drawbacks such as low rate of reaction. In the present study we have attempted to enhance the concentration of sugars in enzymatic hydrolysate of delignified Prosopis juliflora, using a fed-batch enzymatic hydrolysis approach.

Results: The enzymatic hydrolysis was carried out at elevated solid loading up to 20% (w/v) and a comparison kinetics of batch and fed-batch enzymatic hydrolysis was carried out using kinetic regimes. Under batch mode, the actual sugar concentration values at 20% initial substrate consistency were found deviated from the predicted values and the maximum sugar concentration obtained was 80.78 g/L. Fed-batch strategy was implemented to enhance the final sugar concentration to 127 g/L. The batch and fed-batch enzymatic hydrolysates were fermented with Saccharomyces cerevisiae and ethanol production of 34.78 g/L and 52.83 g/L, respectively, were achieved. Furthermore, model simulations showed that higher insoluble solids in the feed resulted in both smaller reactor volume and shorter residence time.

Conclusion: Fed-batch enzymatic hydrolysis is an efficient procedure for enhancing the sugar concentration in the hydrolysate. Restricting the process to suitable kinetic regimes could result in higher conversion rates.

No MeSH data available.