Precipitants of Lactobacillus casei ATCC 393-loaded chitosan microspheres were prepared by electrostatic interaction between chitosan (CS) and poly-gamma-glutamic acid (gamma-PGA). The loading efficiency was approximately 80%, and the zeta potential of the microspheres became more positively charged as the molar ratio of the chitosan amino group was increased. The particles were confirmed to have a spherical shape by optical microscopy. A release test using simulated gastric fluid (SGF) was also performed. The results show that the precipitants were gradually released from the CS-gamma-PGA microspheres at a rate of almost 80% after 60 min. Both the inhibition of Helicobacter pylori growth and the anti-adhesive activity of encapsulated precipitants were maintained after exposure to SGF. These results indicate that CS-gamma-PGA microspheres may provide a delivery system for the effective eradication of H. pylori. (C) 2010 Elsevier Ltd. All rights reserved.