Performing under pressure: esterification activity of dry fermented solids in subcritical and supercritical CO2

Objective Lipases are often used in immobilized form, but commercial immobilized lipases are costly. An alternative is to produce lipases in solid-state fermentation, dry the solids and then use the dry fermented solids (DFS) directly. We produced DFS by growingBurkholderia contaminanson a mixture of sugarcane bagasse and sunflower seed meal and used the DFS to esterify oleic acid with ethanol in subcritical and supercritical CO(2)at 40 degrees C. Results Compared to a control without CO(2)at atmospheric pressure, subcritical CO(2)at 30 bar improved esterification activity 1.2-fold. Higher pressures, including supercritical pressures up to 150 bar, reduced activity to less than 80% of the control. At 30 bar, the esterification activity was improved a further 1.8-fold with the addition of 9% water (i.e. 9 g water per 100 g oleic acid) to the reaction medium. Conclusion A subcritical CO(2)atmosphere, with the addition of a small amount of water, improved the esterification activity of DFS containing lipases ofBurkholderia contaminans.

Automated summary

By growing Burkholderia contaminans on a mixture of sugarcane bagasse and sunflower seed meal, dry fermented solids (DFS) were produced and used for oleic acid esterification in subcritical and supercritical CO(2) at 40 degrees Celsius. Results showed that esterification activity was improved 1.2-fold under subcritical CO(2) at 30 bar, but decreased to less than 80% of the control at higher pressures, including supercritical pressures up to 150 bar. The addition of 9% water to the reaction medium at 30 bar further improved esterification activity by 1.8-fold.