Why does the sample appear viscous after sample Lysis and not pass through the column easily, even when less than the suggested maximum sample amount is used?"

If a sample is rich in protein, complete digestion will not be achieved using the amount of Proteinase K and buffer suggested in the protocol. If a sample cannot be digested completely or appears very viscous, add more Lysis Buffer and repeat incubation. Centrifuge the sample at full speed for 5 minutes to remove undigested remains and only use the supernatant in the following steps. In the subsequent preparations, a lower amount of the sample should be used. A general rule of thumb is to start with half of the maximum amount of sample suggested. When there isn’t a problem in digesting the sample completely or passing the lysate through the column, the sample amount can be increased gradually in the subsequent preparations.