Inversion of sucrose by immobilized invertase follows a substrate inhibited kinetics. The reaction rate (v) in mol m^-3 h^-1 can be expressed as:
$$v = \frac{{800[S]}}{{\left\{ {400 + 50[S] + {{[S]}^2}} \right\}}};$$      where [S] is the sucrose concentration.
The immobilized invertase preparation is used in a CSTR with 100 mol m^-3 sucrose concentration in the feed stream. If the reaction velocity passes through a maximum at [S] = 20 mol m^-3 the feed flow rate for a reactor volume of 1 m³ to get the maximum productivity from the reactor should be