The influence of immobilization and reduced water activity on gaseous-alkene oxidation by Mycobacterium PY1 and Xanthobacter PY2 in a gas-solid bioreactor

Immobilization of Mycobacterium PY1 and Xanthobacter PY2 in alginate and in or on hydroculture has a minor influence on the maximum rate of oxidation of propene and ethane. The apparent K(m) values of the immobilized cells are slightly higher than those of the free cells, indicating the presence of diffusion limitation in the immobilized systems. Both bacterial strains rapidly lose their alkene-oxidizing activity when the water activity is decreased. This decrease in activity is so rapid that most of the activity is lost already when the pores of the pertinent supports are still filled with water. Therefore, it is not possible with this system to study the transition of mass transfer of substrates entirely in the water phase to mass transfer to substrates entirely through the gas phase.