Thank you Bjorn,

It is a very interesting method. Unfortunately, that will not resolve my problem because it is an offline method and will need several steps of extraction ... what I need is a quick method that can deal with the quick evolution of the biomass concentration in a bioreactor

Thank you Sezer,

qRT-PCR is also interesting when the needed material is available. But it is also an offline method and it takes a longer time than the quick evolution in bioreactor.

Thank you again Bjorn,

I hope that your colleagues may have the solution for my problem.

Could you use optical density? This would be related to the fungal biomass.

Hi Jack,

optical density is related to bacterial biomass but not to fungal biomass because the latter is often formed as bigger particules and will make solution completly opaque

In the 1990s we had a related (but simpler) challenge with biomass measurements in algal growth inhibition testing. We developed a very simple analytical method, where 0.2 mL of sample was mixed with 0.8 mL of Acetone/DMSO (1:1, vol:vol). This had the effect that biological processes were turned off, the cells lyzed and the photopigments were brought into an extracted form. We could then measure the fluorescence of the photopigments with a conventional fluorescence spectrophotometer. This in vitro fluorescence was then used as a surrogate for biomass. The method was practical, time efficient and is still used in algal growth inhibition testing and also referred to in a number of international standards. The method has also been used for algal toxicity testing of soil suspensions, meaning that it is rather robust with regards to particles. Reference: Mayer et al, 1997, Water Research 31:2525-2531.

https://www.researchgate.net/publication/223918536_A_simple_in_vitro_fluorescence_method_for_biomass_measurements_in_algal_growth_inhibition_tests?ev=prf_pub

Maybe you can use a similar approach with fungal biomass. First, mix the sample with a water miscible solvent (DMSO, Acetone, Ethanol), this could be done on discrete samples or also in a flow (Challenge: sufficient extraction might take time or accelerated conditions). Second, you could then measure ergosterol in the extract, maybe by HPLC or an online spectrophotometer (Challenges: sensitivity and separation of particles from extract). I am not working with fungal biomass in bioreactors, so this are just ideas for inspiration.

Article A simple in vitro fluorescence method for biomass measuremen...

Thank you Philipp,

this is a very inspirational proposition and may be very pratical if it works.

Determinate of Carbon content before and after fumigation

Calcofluor White is a compound that fluoresces when it binds to chitin in fungal cell walls. Maybe you can construct a calibration curve using that compound by simply mixing it with mycelia. It would be a non-destructive method.

Interesting idea. Fluorescence would allow very simple measurements even at very low concentrations. Maybe this can be combined with the addition of 10-80 % solvent (see earlier response).

Hi Zia,

optical density is related to bacterial biomass but not to fungal biomass because the latter is often formed as bigger particules and will make solution completly opaque making OD reading very difficult and non-repeatable

I think we need to be very carefull in using optical density which is basically a type of turbidimetry. That means the measurement is based on any particulate matters capable of absorbing light at the spesific wavelength applied. This include bacterial cells, other cells and even non biological matters. Optical density may be a good indicater for cells counting, but probably will require other methods (as suggested by previous participant/researcher above) to confirm the cell numbers. This is especially important if we want to measure the actual living cells