problems with yields from qiagen spin mini prep kit - (Jan/25/2007 )

Most likely the problem is with the source of your culture. Are you starting from a fresh transformant, plating, and then plucking a single colony and then growing overnight, or are you going from glycerol stock. If going from glycerol stock you must re-streak and then pluck a healthy (large) colony to grow your overnight, of course assuming that your glycerol stock is a log phase culture.