For the formulation and sustained-release delivery of pyrrolnitrin, a biologically anti-fungal antibiotic, a microencapsulation technique using gluten and casein as the coating materials and employing simple coacervation was developed. The core materials were the dried fermentation broth of Pseudomonas cepacia containing pyrrolnitrin (Powder A) and pyrrolnitrin-adsorbed Microken powder (Powder B). Irregular microcapsules with particle sizes ranging from 5 to 80 mu m and possessing a smooth surface after hardening with glutaraldehyde were obtained. For the encapsulation of Powder B, about 51-69% of pyrrolnitrin was retained in the microcapsules; compared with only 27-48% for the encapsulation of Powder A, These low yields were due to the decomposition of pyrrolnitrin, as well as to its release into the polymer-poor phase during the coacervation process. Microcapsules prepared by each of the dispersion systems conferred significant delayed-release of pyrrolnitrin, compared to its rapid release from the core materials without encapsulation. The sustained release properties depended on both the core-to-wad ratio and the dosage of hardening agent.