Is an additional proteinase K digest possible with DNeasy PowerSoil Kit and DNeasy PowerLyzer Kit?
FAQ ID - 3725

The sample material will be lysed with a bead beating method with DNeasy PowerSoil Kit and DNeasy PowerLyzer Kit. However, when needed, an additional proteinase K digest will work in Buffer C1/PowerBeadSolution mixture. The PowerBead Solution comes pre-loaded in the PowerBead Tube in DNeasy PowerSoil but is added to the Bead Tube separately in DNeasy PowerLyzer PowerSoil Kit. The incubation should be done in 750 ul PowerBead Solution + 65 ul Solution C1. 

Our recommendation is to add 20 ul of Proteinase K (20 mg/ml) to the sample in Buffer C1/ PowerBeadSolution mixture and incubate at 65 °C for 30 minutes. For this purpose, QIAGEN Proteinase K (10 ml) can be purchased under catalog number 19133 or QIAGEN Proteinase K (2ml) under catalog number 19131.