Table 2.

Schematic experimental design of the two conducted experiments in which two clearly distinct activities are described

Aim	Samples characteristics	Sample origin	Schedule of DNA extraction
Comparing the extracted DNA concentration in fresh and frozen samples	4 types of samples named A, B, C and D	Sludge from anaerobic digestion of WWTP	For each sample: DNA extraction from fresh sample and DNA extraction from 10-days frozen sample
Verifying the preservation of the extracted DNA concentration in frozen samples	2 samples, named E and F	Sludge from anaerobic digestion of OFMSW	Repeated DNA extractions from aliquots of the same sample after different storage periods