Chemoselective transesterification of wood steroles by lipases
The chemoselective transesterification of wood sterols is a novel type application of lipases that is considered within a technological platform for the upgrading of black liquor from the Kraft pulping process. Wood sterols are a mixture of sterols and stanols (saturated sterols) in which more than 90% is represented by β-sitosterol and β-sitostanol. Both products are oriented to different markets, representing the fractionation of the wood sterols a significant added value. Both substances are structurally similar which precludes its separation by physical operations, being its fractionation by chemoselective esterification with lipases a very appealing strategy. Several commercial lipases were evaluated in their capacity for the selective transesterification of stanols and two of them were selected: one immobilized and one non-supported. The process was optimized with the immobilized lipase obtaining more than 90% esterification of sterols with around 20% esterification of sterols, which satisfied the criterion of selectivity. The immobilized enzyme was however poorly stable because of protein desorption during the reaction; therefore, several strategies of immobilization of the non-supported lipase were developed, best results being obtained with butyl Sepabeads® as support. The selected biocatalyst was tested in the sequential batch reaction of transesterification, proving that the biocatalyst can be used for five sequential batches with very little loss of activity and insignificant reduction in conversion and productivity, which satisfies the profitability criterion of the process. Key words: Lipase; enzymatic transesterification; wood sterols; stanol esters; immobilized enzyme.
| Main Authors: | , , |
|---|---|
| Format: | Digital revista |
| Language: | spa |
| Published: |
Universidad Nacional de Colombia - Sede Bogotá - Instituto de Biotecnología
2008
|
| Online Access: | https://revistas.unal.edu.co/index.php/biotecnologia/article/view/1400 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | The chemoselective transesterification of wood sterols is a novel type application of lipases that is considered within a technological platform for the upgrading of black liquor from the Kraft pulping process. Wood sterols are a mixture of sterols and stanols (saturated sterols) in which more than 90% is represented by β-sitosterol and β-sitostanol. Both products are oriented to different markets, representing the fractionation of the wood sterols a significant added value. Both substances are structurally similar which precludes its separation by physical operations, being its fractionation by chemoselective esterification with lipases a very appealing strategy. Several commercial lipases were evaluated in their capacity for the selective transesterification of stanols and two of them were selected: one immobilized and one non-supported. The process was optimized with the immobilized lipase obtaining more than 90% esterification of sterols with around 20% esterification of sterols, which satisfied the criterion of selectivity. The immobilized enzyme was however poorly stable because of protein desorption during the reaction; therefore, several strategies of immobilization of the non-supported lipase were developed, best results being obtained with butyl Sepabeads® as support. The selected biocatalyst was tested in the sequential batch reaction of transesterification, proving that the biocatalyst can be used for five sequential batches with very little loss of activity and insignificant reduction in conversion and productivity, which satisfies the profitability criterion of the process.
Key words: Lipase; enzymatic transesterification; wood sterols; stanol esters; immobilized enzyme. |
|---|