We are measuring filamentous bacterial biomass in bioprocesses using a capacitance probe (biomass monitor from Aber). In the log phase the biomass signal is growing, as is the viscosity of the culture, and after it reaches a platou, the biomass monitor signal starts to increase again. The viscosity though, starts to decline at the same poin. The viscosity drop is due to morphological changes of the culture (the micelia are fragmenting, still viable). So I think that the capacitance increase must be artificial, due to increase in cell entities not due to increase in biomass. Does anyone have a good explanation for this? Or in other words, is and why is the capacitance of a long hyphe lower than the capacitance of a number of short hyphal fragments with the same biomass?

Any suggestions for a bether method for biomass monitoring in a very complex medium with filamentous bacteria cilture that has non-newtonian fluid properties? :)