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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.


Kinetic simulation profile for the volume of bioreactor at different initial substrate consistency (5-15%) using dilution rate of (A) 0.1 h-1, (B) 0.2 h-1, (C) 0.3 h-1 and (D) 0.4 h-1.
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Figure 6: Kinetic simulation profile for the volume of bioreactor at different initial substrate consistency (5-15%) using dilution rate of (A) 0.1 h-1, (B) 0.2 h-1, (C) 0.3 h-1 and (D) 0.4 h-1.

Mentions: The kinetic parameters determined from the batch experiments were used to simulate different feeding policies. These simulations provide an insight about the operational protocol that may be implemented to obtain the best hydrolysis results. The simulation of discussed kinetic model under the fed-batch optimization approach has been shown in Figure 5 and 6. The Figure 5 depicted four different feeding policies developed from simulations with the target cumulative insoluble solids in the reactor as 20%. The simulation results showed that the cumulative insoluble solid concentration increases with time and saturates at different final values depending on the initial feed concentration at dilution rates of 0.1-0.4 h-1 (Figure 5). The results indicated that long residence times are required to reach these higher solids levels, when solids were controlled at 5% or lower (Figure 5). While, the simulation results in Figure 6 indicated that higher insoluble solids levels in the feed resulted in both smaller reactor volumes and shorter residence times to achieve a given feeding objective. However, it has been predicted from the simulation results that the feed controlled at 10% initial solid levels resulted in maximum saccharification.


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)

Kinetic simulation profile for the volume of bioreactor at different initial substrate consistency (5-15%) using dilution rate of (A) 0.1 h-1, (B) 0.2 h-1, (C) 0.3 h-1 and (D) 0.4 h-1.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Kinetic simulation profile for the volume of bioreactor at different initial substrate consistency (5-15%) using dilution rate of (A) 0.1 h-1, (B) 0.2 h-1, (C) 0.3 h-1 and (D) 0.4 h-1.
Mentions: The kinetic parameters determined from the batch experiments were used to simulate different feeding policies. These simulations provide an insight about the operational protocol that may be implemented to obtain the best hydrolysis results. The simulation of discussed kinetic model under the fed-batch optimization approach has been shown in Figure 5 and 6. The Figure 5 depicted four different feeding policies developed from simulations with the target cumulative insoluble solids in the reactor as 20%. The simulation results showed that the cumulative insoluble solid concentration increases with time and saturates at different final values depending on the initial feed concentration at dilution rates of 0.1-0.4 h-1 (Figure 5). The results indicated that long residence times are required to reach these higher solids levels, when solids were controlled at 5% or lower (Figure 5). While, the simulation results in Figure 6 indicated that higher insoluble solids levels in the feed resulted in both smaller reactor volumes and shorter residence times to achieve a given feeding objective. However, it has been predicted from the simulation results that the feed controlled at 10% initial solid levels resulted in maximum saccharification.

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.