Chiang Mai Journal of Science

     Encapsulation of plant growth-promoti ng rhizobacteria (PGPR) is a powerful strategy to support agricultural sustainability by increasing plant growth and yield, while reducing the use of chemical fertilizers. This study aimed to assess candidate formulations to encapsulate Priestia aryabhattai KNB6 using sodium alginate supplemented with alternative organic additi ves, by determining bead properties and bacterial survival. In addition, the effects of encapsulated KNB6 on rice growth, nutrient uptake, and rice development were investigated. Encapsulating P. aryabhattai KNB6 with 2% sodium alginate enriched with 1% skim milk provided the favorable properties of the smallest microbead size (0.31 mm), the highest encapsulati on efficiency (99.5%), and the greatest bacterial survival (100%). Scanning electron microscope (SEM) imaging exhibited oval bead shape with P. aryabhattai KNB6 embedded in alginate-skim milk matrix visible on bead surface. In a release test the encapsulated bacteria had multiplied in the beads and were continuously released from microbeads effecti vely carrying 10⁸ CFU/g. For plants grown in soil with limited availability of P, inoculation of KNB6 either as cells or in encapsulated form increased plant growth by its P solubilizing activity. In the pot experiments with application of chemical fertilizer, inoculation with KNB6 conferred better plant growth and development than without these bacteria. KNB6 free cells and encapsulated KNB6 increased plant dry mass by 109.7% and 74.9%, with chlorophyll contents raised by 10.3% and 5.1%, respectively. Nutrient uptake of plants treated with free KNB6 cells and immobilized ones improved, especially in their N and P adsorption increases by 82.3% and 86.1% and 47.4% and 33.4%, respectively. Moreover, all the treated plants developed obvious rice cracking. The results demonstrate that the encapsulated form of P. aryabhattai KNB6 has potential to be developed to serve as a bio-inoculant that increases soil nutrient availability and improves plant growth, thereby supporti ng sustainable agriculture.