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.
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? "