Growth adaptation of probiotics in biopolymer-based coacervate structures to enhance cell viability

•Enhancement of the viability of microencapsulated probiotics in complex biopolymer coacervates.•Encapsulated cells metabolized nutrients and multiplied within the coacervate structures.•Post culture in coacervates provided significant cell protection to applied stresses.•Cells in coacervates embedded in gel microspheres exhibited enhanced viability.

The effect of inoculum size and growth of probiotic cells inside biopolymer-based coacervate structures, made from whey protein isolate and gum arabic, and a dual encapsulation method of complex coacervation coupled with ionotropic gelation on the survival of probiotics was evaluated under adverse environmental conditions; i.e. low pH, heating, and simulated gastric juice (SGJ). The encapsulated bacteria metabolized nutrients and multiplied within the coacervate structural assemblies, pointing to a rather open carrier-delivery system for microbial cells, allowing the exchange of metabolites and nutrients with the bulk liquid medium. Encapsulation of probiotic cells at low counts and subsequent growth improved cell viability upon heating or exposure to SGJ. When cells entrapped in complex coacervates were subsequently embedded in Ca2+-alginate gel microspheres, the remaining viable counts at pH 2.0 for 3 h were even higher by almost 1 logCFU/g. Overall, an initial low inoculum size of bacteria in complex coacervates, followed by culture growth (adaptation stage) and subsequent entrapment in alginate microspheres greatly enhanced the cell viability of probiotic cultures.