Thermal inactivation of native and crosslinked invertases

Formaldehyde and three homobifunctional bisimidoesters having different lengths, dimethyl suberimidate (DMS), dimethyl adipimidate (DMA), dimethyl-3,3'-dithiobispropionimidate (DTBP), were used to crosslink invertase. Optimal concentrations for crosslinking with DMS and formaldehyde were determined as 0.3% and 0.015%, respectively. Inactivation mechanisms of the native, DMS and formaldehyde cross-linked invertases were first order during prolonged heat treatment. The maximum stabilization 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, crosslinking with DMA and DTBP decreased stability against inactivation.