There are a number of sterilizing filter grades out there. They are generally pleated polymer membrane filter cartridges and will remove down to 0.2 micron, which is the smallest known bacteria size. Some membrane types are better at removing cellular debris than others, due to adsorptive characteristics. Your best bet is to contact a technical service representative and give them a sample of your oil, fluid characteristics, process conditions and quality measurement criteria. I work with a number of experts in this particular field, and they often specify end filtration of centrate. You can get technical advice from either of the following companies: Pall, Cuno, or Millipore. Each of them is likely to have a distributor in your neighborhood. Also, if you have particular questions and some specifics, I could probably get you a number of the answers you are looking for.
ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee