I am extracting DNA from soil sample based on Zhou's conventional method but I am facing problems with the humic acids. The humic acids will decrease the purity of DNA and thus, inhibits the downstream process. Is there any method to remove this?
We tried a couple of modifications to Zhou's protocol, to make it work for compost DNA. As Yugal stated, we found using PEG to preciptate helped (LaMontagne et al. 2002). After PEG precipitation go immediately into CTAB/choloroform extraction and you should see the humic acids go into the CTAB interface.