Diplogelasinospora grovesii IMI 171018 immobilized in polyurethane foam. An efficient biocatalyst for stereoselective reduction of ketones.

Diplogelasinospora grovesii has been reported as a very active biocatalyst in the reduction of ketones. Along the text, the properties of this filamentous fungus as an immobilized catalyst are described. For this purpose, several immobilization supports as agar and polyurethane foam were tested. Experimental assays were also performed to test different co-substrates for the regeneration of the required enzyme cofactor. The fungus immobilized in polyurethane foam lead to the most stable and active catalyst. This derivative, using i-PrOH as co-substrate, could be reused at least 18 times without appreciable activity loss (>90% activity remains). Kinetic runs experiments shown that the reduction of cyclohexanone, selected as model substrate, followed a pseudo-first kinetic order and that the rate controlling step was the mass transfer through the cell wall. The deactivation kinetic constants were also determined. The reduction of different chiral ketones showed that the ketone reductase activity followed the Prelog's rule.

Monascus kaoliang CBS 302.78 immobilized in polyurethane foam using iso-propanol as co-substrate: Optimized immobilization conditions of a fungus as biocatalyst for the reduction of ketones.

Monascus kaoliang was selected after a microbial screening as a highly active and selective whole cell catalyst for the reduction of ketones. In the present paper we describe the optimum growing conditions and an interesting immobilization procedure by adsorption in polyurethane foams (PUFs). This methodology is easy to perform and the immobilized catalyst is active, stable and reusable. The use of different co-substrates for cofactor regeneration was also tested and iso-propanol (i-PrOH) was found as the best co-substrate, as it leads to a catalyst reusable for 17 cycles, displaying better NADH regeneration properties than others e.g., glucose (10 cycles) or saccharose (6 cycles). The reduction of different prochiral ketones showed that the ketone reductase activity of this mould follows the Prelog's rule and kinetic experiments demonstrated that the process follows a pseudo-first kinetic order.