1. The problem statement, all variables and given/known data Which of the following methods is suitable to sterilize a liquid medium,containing blood serum? (1) pasteurization (2) Autoclaving at 121degrees celsius for 10 minutes (3) Boiling at 100 degree celsius for 10 minutes (4) Filtration using a sterile membrane filter (5) Freezing at -20 degrees celsius Ans given is (2) 2. Relevant equations n/a 3. The attempt at a solution I don't understand why it can't be (4).Why can't we use a sterile filter to sterilize blood serum,afterall sterilization is to remove or kill any microorganisms present in a medium,right? My other question is,isn't blood serum a thermolabile medium so how can we sterilize it by heating it,without denaturing any of the plasma proteins present?