I have for a while experienced very little or no yeild with maxipreps of my plasmids (vector + insert = 10 kb). At the moment I use Sigmas maxiprep kit (but I have also tried kits from Jet star and Qiagen). However I dont think it is the kit that is the problem. I always pick fresh colonys in 2ml LB + Amp(always newly autoclaved solutions and fresh amp) incubate over night (37oC, shaking)and perform minipreps on. The minipreps always have good yield and restriction cleavage shows I have the correct product.
The problems arise after this step: I incubate (same conditions as above) LB, amp and a little from the miniculture (1/1000 of the total vol) over night. I control that OD at 600 nm is the desired one and then perform maxipreps. Since I didnt have any maxi yield last time I also performed a miniprep on I.5 ml of the maxiculture showing also no product, indicating that something must have happened during the incubation of the maxi culture, but I just cant figure out what is going wrong?