Microencapsulation of Bacillus subtilis by spray-drying using starch hydrolysates with different dextrose equivalent values

Abstract

Sustainable agricultural practices require innovative solutions to enhance productivity while reducing environmental impact. The use of plant growth-promoting microorganisms, such as Bacillus subtilis, as biofertilizers is a promising strategy. However, ensuring cell viability during storage and under field conditions remains a challenge. This study investigates the encapsulation of B. subtilis via spray-drying using starch hydrolysates with different dextrose equivalent (DE) values (DE-8, DE-18, and DE-38) as wall materials. Encapsulation efficiency was approximately 80 % for all formulations. The DE values influenced microcapsule morphology and cell release profiles, with higher DE materials producing smoother, smaller, and more homogeneous particles. The microcapsules effectively protected cells against high salinity and acidic pH stresses. Thermal stability was significantly improved with DE-18 and DE-38, maintaining over 95 % viability after 72 h at 50 ◦C. Under UV exposure, DE-18 demonstrated superior protection. Storage stability tests confirmed enhanced longevity for encapsulated cells compared to free bacteria, with higher DE microcapsules demonstrating better resilience to elevated temperatures. These findings highlight the potential of starch-based microencapsulation to improve biofertilizer performance, ensuring microbial survival and efficacy in diverse environmental conditions.