	Two Phase Systems - In this approach, a water immiscible material (the second phase) is used to remove the product from aqueous broth (the first phase). The second phase may be either present in the fermentation broth or located in a separate chamber through which the broth is passed for removal of the product.
The second phase may either be a liquid, e.g., n-hexane, n-octane, etc., or a solid. Liquid second phase has been used for the separation of products like butyric acid, valeric acid, caproic acid from suppressed methane anaerobic fermentation. Adsorbants like activated charcoal, etc. have been employed for the in situ recovery of a variety of products. Anion exchange resin has been used to remove salicylic acid during fermentation of naphthalene by Pseudomonas aeruginosa; this greatly increases salicylic acid yields.