We are currently having problem sterilize certain mixture of substrates containing some heat resistant spore forming bacteria, it is usually a single phenotype instead of a mixture.

We do not know the initial biomass since it is pretty much just half sterilized dirt with compost, we wish to find out the initial biomass after the sterilization to determine an acceptable biomass for our mycelium to overpower.

What I am planning is, after the sterilization process we inoculate a set amount of simple media such as TSB with a set weight of substrate and allow it to incubate for maybe 48 hours to 120 hours.

After 48 hours we can then filter the media via 0.2um filter and exsiccate the material together with the filter.

We then compare the weight between a dry filter plus dry substrate of the same amount to the finished product, the difference should be the weight of bacteria.

Once we identifies the species of the bacteria then we can calculate the initial biomass in weight by finding out it's proliferation rate. We do not need a super accurate result.

Anyone else have a better idea? We currently do not have a high speed centrifuge but it is within budget to get a simple one with up to 3000-3500g.