THERMAL INACTIVATION OF NATIVE AND CROSS-LINKED INVERTASES

Formaldehyde and three homobifunctional bisimidoesters having differen t lengths, dimethyl suberimidate (DMS), dimethyl adipimidate (DMA), di methyl-3,3'-dithiobispropionimidate (DTBP), were used to crosslink inv ertase. Optimal concentrations for crosslinking with DMS and formaldeh yde were determined as 0.3% and 0.015%, respectively. Inactivation mec hanisms of the native, DMS and formaldehyde cross-linked invertases we re first order during prolonged heat treatment. The maximum stabilizat ion factors with DMS and formaldehyde were 1.5 at 55 degrees C and 1.7 at 57.5 degrees C, respectively. V-max and K-m values decreased 5 to 10% by DMS and formaldehyde crosslinking. On the other hand, crosslink ing with DMA and DTBP decreased stability against inactivation.