If your genomic DNA is contaminated with polysachharides, it do look viscous. did u carried out purification process? Try to purify twice. Then dilute the DNA in 1:10 or 1:100 ratio. Then proceed for 16S amplification.

Of Course, I did purification and I will do it again combining with dilution

Thanks

did you measure the concentration of DNA? if it is 2 or more ug/ul(viscous) then I would dilute first before making PCR.

Thanks for all, the PCR problems was solved after second purification using QIAGEN PCR purification kit combined with 4 times dillution.

Best Regards