## Materials and Methods
Next, the precipitate was re-suspended in PBS for further encapsulation by alginate beads. Then, the encapsulation state of the FKC inside the alginate bead was investigated by either SEM (FE-SEM, FEI Quanta FEG250, Hillsboro, OR, USA), fluorescence microscopy (iRis Digital Cell Imaging System, Logos biosystems, Anyang-Si, Korea) or the use of confocal microscopy (Confocallaser scanning microscope SP8 X, Leica, Wetzlar, Germany). For the specimen of the SEM measurement, an alginate bead was dried under ambient air and was then crushed into pieces. Next, the pieces were placed onto a sticky carbon tape and were sputtered with Pt/Pd plasma for 60 s. Before fluorescence and confocal microscopy, wet alginate beads containing FITC-FKC were pressed on a slide glass utilizing a coverslip and were subjected to a microscopic analysis. To confirm the possibility of FKC quantification by green fluorescent marker, we mixed 1 mL of FKC suspension with \(1\times 10^{9}\) cells/mL concentration. Then, the suspension was diluted with PBS obtained from the FKC-FITC concentrations of \(5\times 10^{4}\), \(1\times 10^{5}\), \(2\times 10^{5}\), \(4\times 10^{5}\), \(6\times 10^{5}\), \(8\times 10^{5}\) cells/mL. We next prepared six standard samples that were subjected to fluorescence quantification under an excitation wavelength at 492 nm and emission wavelength at 520 nm utilizing a microplate reader ([PERSON](tm) LUX multimode microplate reader, Thermo Fisher Scientific(tm), Waltham, MA, USA). To encapsulate the FKC into alginate bead, the following process was utilized. First, an alginate solution was prepared in 2% (wt/v) concentration. The FKC suspension either with or without clay moiety was prepared as follows: the FKC suspension with OD 0.2 was mixed with an equivalent volume of PBS, KA-PBS suspension (1 mg/mL) and the LDH-PBS suspension (1 mg/mL), respectively. At this time, the alginate solution and FKC suspension (with or without clay) were gently mixed and the mixture was dropped into CaCl\({}_{2}\) solution (0.1 M) utilizing a 20-gauge needle. Finally, alginate beads were readily formed through cross-linking of the alginate chains by Ca\({}^{2+}\) coordination. The encapsulation of the FKC into alginate with or without clays was quantified utilizing FITC-FKC. After the encapsulation process, the supernatant was subjected to a fluorophore analysis under an excitation wavelength of 492 nm and emission wavelength of 520 nm. Here, the encapsulation efficiency (EE) and loading capacity (LC) was calculated by using the equation below. \[EE\ (\%)=\frac{\left( \begin{array}{c}\text{{total {FKC utilized in encapsaps}}}\\ \text{{ulation}}\end{array} \right)-\text{FKC in supernatant}}{\text{total {FKC utilized in encapsulation}}}\times 100\]  
\[LC=\frac{\text{number of {FKC inside the bead}}}{\text{total {dried weight of alginate bead with FKC}}}\]  
In this study, FKC release was quantified under three different solutions: deionized water (DW), simulated gastric solution, and simulated intestinal solution. The simulated gastric solution was prepared by adjusting the acidity of the aqueous NaCl solution (0.002%) to pH -1.2 utilizing hydrochloric acid, and the simulated intestinal solution was prepared by mixing 250 mL KH\({}_{2}\)PO\({}_{4}\) (0.2 M), 76 mL NaOH (0.2 M), and 674 mL DW. The pH of the intestinal solution was -6.5. The alginate bead (-0.1 g) was put into each solution (-20 mL) and was stirred gently at 100 rpm under darkness. At a designated time point (2 h for DW, 4 h for gastric condition and 2 h for the intestinal condition), the supernatant was collected and the predetermined amount of released FKC was quantified by a fluorophore (excitation wavelength of 492 nm and emission wavelength of 520 nm). The time point for DW, gastric, and intestinal condition was determined considering the residence time of the alginate in water before feeding, in the stomach and in the intestine of the fish after feeding.