Alginate–whey protein/chitosan microencapsulation of Lactobacillus casei ZGP-Lca.25 enhances viability and modulates apoptosis in colorectal cancer cells

Colorectal cancer (CRC) remains one of the leading causes of cancer-related mortality worldwide, and resistance to conventional therapies highlights the need for novel adjunctive treatment strategies. Although Lactobacillus casei ( L. casei ) has shown promising anticancer potential, its poor survival under gastrointestinal conditions limits its therapeutic application. In this study, we investigated whether alginate–whey protein microencapsulation with a chitosan coating could overcome the poor gastrointestinal survival of L. casei while preserving its selective anticancer activity against colorectal cancer cells. L. casei ZGP-Lca.25 was encapsulated using an alginate–whey protein matrix coated with chitosan, and encapsulation efficiency and microcapsule characteristics were assessed. The viability of encapsulated probiotics was evaluated under simulated gastrointestinal conditions. Cytotoxic effects on HT-29 colorectal cancer cells and human dermal fibroblast (HDF) cells were evaluated using the MTT assay, and the expression of apoptosis-related genes ( BAX and BCL-2 ) was analyzed by quantitative real-time PCR (qRT-PCR). Encapsulation efficiency reached 97.17%. Encapsulated L. casei exhibited significantly higher survival in simulated gastric (3.57 ± 0.29 log CFU/mL) and intestinal (3.65 ± 0.27 log CFU/mL) fluids, whereas free bacteria became non-viable after 120 min. Although encapsulated L. casei showed a higher IC₅₀ (1 × 10⁷ CFU/mL) than the free preparation, it retained significant selective anticancer activity by upregulating BAX and downregulating BCL-2 in HT-29 cells without affecting HDF cells. These findings demonstrate that alginate–whey protein/chitosan microencapsulation substantially enhances probiotic gastrointestinal survival while preserving apoptosis-mediated selective anticancer activity, supporting its potential as a probiotic-based adjunctive strategy for colorectal cancer and warranting further in vivo investigation.