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Effect of mixing on enzymatic hydrolysis of steam-pretreated spruce: a quantitative analysis of conversion and power consumption.

Palmqvist B, Wiman M, Lidén G - Biotechnol Biofuels (2011)

Bottom Line: In addition, the results were related to the power input needed to operate the impeller at different speeds, taking into account the changes in rheology throughout the process.A marked difference in hydrolysis rate at different impeller speeds was found.For example, the conversion was twice as high after 48 hours at 500 rpm compared with 25 rpm.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemical Engineering, Lund University, Box 124, Se-221 00 Lund, Sweden. benny.palmqvist@chemeng.lth.se.

ABSTRACT

Background: When scaling up lignocellulose-based ethanol production, the desire to increase the final ethanol titer after fermentation can introduce problems. A high concentration of water-insoluble solids (WIS) is needed in the enzymatic hydrolysis step, resulting in increased viscosity, which can cause mass and heat transfer problems because of poor mixing of the material. In the present study, the effects of mixing on the enzymatic hydrolysis of steam-pretreated spruce were investigated using a stirred tank reactor operated with different impeller speeds and enzyme loadings. In addition, the results were related to the power input needed to operate the impeller at different speeds, taking into account the changes in rheology throughout the process.

Results: A marked difference in hydrolysis rate at different impeller speeds was found. For example, the conversion was twice as high after 48 hours at 500 rpm compared with 25 rpm. This difference remained throughout the 96 hours of hydrolysis. Substantial amounts of energy were required to achieve only minor increases in conversion during the later stages of the process.

Conclusions: Impeller speed strongly affected both the hydrolysis rate of the pretreated spruce and needed power input. Similar conversions could be obtained at different energy input by altering the mixing (that is, energy input), enzyme load and residence time, an important issue to consider when designing large-scale plants.

No MeSH data available.


Related in: MedlinePlus

Conversion during hydrolysis of pretreated spruce for different impeller speeds. (A, B) Conversion during hydrolysis of pretreated spruce (10% water-insoluble solids; WIS) for different impeller speeds (squares = 500 rpm; stars = 300 rpm; circles = 150 rpm; crosses = 75 rpm, diamonds = 25 rpm). (C, D) Conversion at different impeller speeds for three selected times (Circles = 96 hours, diamonds = 48 hours, squares = 24 hours). (A, C) Solid lines = enzyme load of 20 FPU/g glucan; (B, D) dashed lines = 10 FPU/g glucan. The SD in the measured concentrations was < 4.2% for the duplicates.
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Figure 1: Conversion during hydrolysis of pretreated spruce for different impeller speeds. (A, B) Conversion during hydrolysis of pretreated spruce (10% water-insoluble solids; WIS) for different impeller speeds (squares = 500 rpm; stars = 300 rpm; circles = 150 rpm; crosses = 75 rpm, diamonds = 25 rpm). (C, D) Conversion at different impeller speeds for three selected times (Circles = 96 hours, diamonds = 48 hours, squares = 24 hours). (A, C) Solid lines = enzyme load of 20 FPU/g glucan; (B, D) dashed lines = 10 FPU/g glucan. The SD in the measured concentrations was < 4.2% for the duplicates.

Mentions: The conversion of glucan to glucose was strongly affected by impeller speed (Figure 1a-b), for both high and low enzyme loadings (20 FPU/g glucan and 10 FPU/g glucan, respectively). At the highest impeller speed (500 rpm), the conversion after 48 h was more than twice as high as that seen with the lowest impeller speed (25 rpm), that is, 57% compared with only 26% conversion. Furthermore, an almost linear relationship between impeller speed and conversion was found for both enzyme loadings, and interestingly, the positive effect of mixing seemed to be maintained throughout the hydrolysis and did not decrease with time (Figure 1c-d). In fact, it seemed that the influence of mixing increased the further the hydrolysis proceeded, as indicated by the steeper slope of the curves.


Effect of mixing on enzymatic hydrolysis of steam-pretreated spruce: a quantitative analysis of conversion and power consumption.

Palmqvist B, Wiman M, Lidén G - Biotechnol Biofuels (2011)

Conversion during hydrolysis of pretreated spruce for different impeller speeds. (A, B) Conversion during hydrolysis of pretreated spruce (10% water-insoluble solids; WIS) for different impeller speeds (squares = 500 rpm; stars = 300 rpm; circles = 150 rpm; crosses = 75 rpm, diamonds = 25 rpm). (C, D) Conversion at different impeller speeds for three selected times (Circles = 96 hours, diamonds = 48 hours, squares = 24 hours). (A, C) Solid lines = enzyme load of 20 FPU/g glucan; (B, D) dashed lines = 10 FPU/g glucan. The SD in the measured concentrations was < 4.2% for the duplicates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3113933&req=5

Figure 1: Conversion during hydrolysis of pretreated spruce for different impeller speeds. (A, B) Conversion during hydrolysis of pretreated spruce (10% water-insoluble solids; WIS) for different impeller speeds (squares = 500 rpm; stars = 300 rpm; circles = 150 rpm; crosses = 75 rpm, diamonds = 25 rpm). (C, D) Conversion at different impeller speeds for three selected times (Circles = 96 hours, diamonds = 48 hours, squares = 24 hours). (A, C) Solid lines = enzyme load of 20 FPU/g glucan; (B, D) dashed lines = 10 FPU/g glucan. The SD in the measured concentrations was < 4.2% for the duplicates.
Mentions: The conversion of glucan to glucose was strongly affected by impeller speed (Figure 1a-b), for both high and low enzyme loadings (20 FPU/g glucan and 10 FPU/g glucan, respectively). At the highest impeller speed (500 rpm), the conversion after 48 h was more than twice as high as that seen with the lowest impeller speed (25 rpm), that is, 57% compared with only 26% conversion. Furthermore, an almost linear relationship between impeller speed and conversion was found for both enzyme loadings, and interestingly, the positive effect of mixing seemed to be maintained throughout the hydrolysis and did not decrease with time (Figure 1c-d). In fact, it seemed that the influence of mixing increased the further the hydrolysis proceeded, as indicated by the steeper slope of the curves.

Bottom Line: In addition, the results were related to the power input needed to operate the impeller at different speeds, taking into account the changes in rheology throughout the process.A marked difference in hydrolysis rate at different impeller speeds was found.For example, the conversion was twice as high after 48 hours at 500 rpm compared with 25 rpm.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemical Engineering, Lund University, Box 124, Se-221 00 Lund, Sweden. benny.palmqvist@chemeng.lth.se.

ABSTRACT

Background: When scaling up lignocellulose-based ethanol production, the desire to increase the final ethanol titer after fermentation can introduce problems. A high concentration of water-insoluble solids (WIS) is needed in the enzymatic hydrolysis step, resulting in increased viscosity, which can cause mass and heat transfer problems because of poor mixing of the material. In the present study, the effects of mixing on the enzymatic hydrolysis of steam-pretreated spruce were investigated using a stirred tank reactor operated with different impeller speeds and enzyme loadings. In addition, the results were related to the power input needed to operate the impeller at different speeds, taking into account the changes in rheology throughout the process.

Results: A marked difference in hydrolysis rate at different impeller speeds was found. For example, the conversion was twice as high after 48 hours at 500 rpm compared with 25 rpm. This difference remained throughout the 96 hours of hydrolysis. Substantial amounts of energy were required to achieve only minor increases in conversion during the later stages of the process.

Conclusions: Impeller speed strongly affected both the hydrolysis rate of the pretreated spruce and needed power input. Similar conversions could be obtained at different energy input by altering the mixing (that is, energy input), enzyme load and residence time, an important issue to consider when designing large-scale plants.

No MeSH data available.


Related in: MedlinePlus