Development of a Prototype Bio-Product in Pellet Form from Agricultural Residues (Rubber Wood Sawdust and Corn Cobs) Incorporated with Bacillus subtilis

Abstract

At present, the production of agricultural bio-products has become increasingly diverse in both powder and liquid forms. However, limitations in user convenience remain, as most products require mixing or microbial activation prior to application. This study aimed to develop a pelletized bio-product using Bacillus subtilis in combination with agricultural residues, namely, rubberwood sawdust and corn cobs, which serve as carrier materials and nutrient sources. The prototype product was evaluated for bacterial growth efficiency and hydrogel coating performance. The hydrogel coating was prepared from corncob  extract mixed with maltodextrin at a ratio of 1:1, which demonstrated effective coating properties using an encapsulation technique to delay the degradation of the pelletized bio-product. The pelletized bio-product exhibited an initial microbial concentration of 1.52×10⁸ CFU g^-1. After a storage period of 3 months, the survival rate of Bacillus subtilis remained at 6.3×10⁶ CFU g^-1. Scanning Electron Microscopy (SEM) analysis revealed a clearly defined coating layer, which effectively prevented a reduction in bacterial performance. Biodegradation tests conducted through soil burial demonstrated that the hydrogel-coated pellets degraded within 3–4 months, whereas uncoated pellets degraded within 2 days. In distilled water, the coated product maintained its structural stability for more than 2 months. Furthermore, the hydrogel-coated pellets extended the shelf life to more than 6 months, with a microbial survival level of 1.84×10⁵ CFU g^-1. Toxicity and contamination assessments confirmed the absence of harmful residues, highlighting the strong potential of the developed pelletized bio-product for sustainable application in organic agricultural systems.