2.5. Preparation of LAB Supplemented Fish Diet. The isolated
LAB used in this experiment was Lactobacillus plantarum
C014 due to its possession of antimicrobial activity. Its
stock suspension was prepared by suspending the LAB cells
collected from 24 h culture of the bacterium inMRS broth to
obtain a concentration of 1010 CFU/mL.
To prepare the fish diet supplemented with L. plantarum
C014 at the final concentration of 107 CFU/g diet, the bacterial
stock suspension was sprayed into the commercial pellet
fish diet for small catfish slowly, mixing part by part in a
drum mixer. The mixture was passed through a mincedmeat
processing machine, producing extruded strings, which
were dried at 30∘C for 24 h and then broken down to about
2mm long pellets. The diet was transferred to plastic bags
and stored in a freezer (−20∘C) until used. The L. plantarum
C014 supplemented fish diet preparation was repeated every
two weeks. Viability of the incorporated L. plantarum C014
bacterial cells in the dietwas assessed by bacterial isolation on
Lactobacillus selective agar (NEOGEN, Lansing, MI, USA).
The isolated bacterial colonies grown on the medium were
randomly selected to confirmtheir identities by using the API
50 CH system (BioMerieux Industry,Hazelwood,MO, USA).
For the control diet, it was prepared using the same process as
the L. plantarum C014 supplemented diet except adding the
same amount of sterile physiological saline to the commercial
pellet fish diet instead of L. plantarum C014 suspension.