Stability of protein-coated microcrystals in organic solvents

PCMC show very good long-term stability at room temperature, when stored as suspensions in 1-propanol/1 wt.% H2O. Candida antarctica lipase B and subtilisin Carlsberg (SC) in PCMC form retained nearly 90% of their initial activity after 1 year at room temperature (RT). The effects of temperature on the catalytic activity of SC-PCMC are solvent-dependant. In 1-propanol/1 wt.% H2O, the initial rate increased when the temperature was elevated from 25 to 60 °C, whereas in acetonitrile/1 wt.% H2O, SC-PCMC lost activity. The operational stability of PCMC is also solvent-dependant. In 1-propanol/1 wt.% H2O, SC-PCMC lost only 16% of the initial activity after five batch cycles. Rather poor stability was found for SC-PCMC in THF/1% (v/v) H2O and acetonitrile/1% (v/v) H2O, with a rapid loss of activity within 4 h in a continuous flow reactor. However, during the next 4 days only a slow further deactivation was observed.