Biopolymer-Based Gel Capsules for Improved Probiotic Delivery

Biopolymer-based encapsulation represents an effective strategy to enhance probiotic stability and targeted gastrointestinal delivery. In this study, gel capsules composed of sodium alginate (SA) and wheat starch (ST) were developed via extrusion to encapsulate Lacticaseibacillus rhamnosus (L. rhamnosus) and Bacillus clausii (B. clausii), aiming to improve probiotic viability and controlled release. Capsule morphology, color, swelling behavior, encapsulation efficiency, and probiotic survival under simulated gastrointestinal conditions were systematically evaluated as a function of polymer ratio and probiotic loading. Capsule diameters ranged from 236.6 to 279.17 μm and were primarily governed by the SA-ST ratio, with higher ST content yielding smaller, more compact structures. Encapsulation efficiency varied between 71.2% and 96.7%, reaching maximal values in formulations with balanced SA:ST ratios (1:1) and higher probiotic loads. All formulations maintained high cell viability (>96%) following encapsulation. In vitro digestion studies demonstrated that SA-ST capsules significantly enhanced probiotic survival in simulated gastric and intestinal fluids, with the highest cumulative survival observed in ST-rich matrices containing 20% probiotic load. Swelling analyses revealed that ST incorporation promoted controlled hydration and matrix relaxation without compromising structural integrity, supporting sustained release behavior. Overall, the SA-ST biopolymer system provides a simple, scalable, and cost-effective platform for co-encapsulation of L. rhamnosus and B. clausii, offering synergistic protection, high encapsulation efficiency, and improved gastrointestinal stability, with promising applications in functional foods and pharmaceutical formulations.