Removal of suspended solids from tuna spleen extract by microfiltration: A batch process design and improvement

In order to reduce the fouling load during separation of trypsin and chymotrypsin from yellowfin tuna spleen extract by ultrafiltration, a batch concentration microfiltration was designed as a pretreatment process to remove suspended solids from this extract. The design process included both dead-end and crossflow microfiltration (CFMF) to select optimal conditions for operation. The optimal membrane pore size of 0.10 μm was selected by a preliminary test using dead-end microfiltration. And then based on total recycle and single-batch concentration CFMF, a continuous-batch concentration CFMF (CBC-CFMF) with 0.10 μm hollow fiber membrane, crossflow velocity of 0.2 m s−1, transmembrane pressure of 0.15 bar and gas injection factor of 0.38 was designed and applied successfully to remove suspended solids from tuna spleen extract while transmissions of about 1 for both trypsin and chymotrypsin were attained in this study. The negative effects of shear stress, high concentration of feed and long holding time in batch operation process were minimized by CBC-CFMF combined with gas bubbling technique. The optimal gas injection factor (r) of 0.38 resulted in a 300% improvement in flux comparing to the process without gas injection. Higher gas injection factor caused damage on both transmission and activity of expected enzymes. A clear permeate with slight yellow colour was obtained after CBC-CFMF.