Development of starch–alginate–PVA hydrogel beads for encapsulation and sustained delivery of Trichoderma longibrachiatum in Capsicum annuum
Abstract
Sustainable microbial delivery systems can improve the stability and effectiveness of bioinoculants in agriculture. In this study, a starch–alginate–PVA hydrogel was developed to encapsulate Trichoderma longibrachiatum by ionic gelation. The beads showed uniform spherical morphology, high moisture retention (86.17 ± 1.8%), swelling capacity (233 ± 5.4%), and encapsulation efficiency (87.0 ± 2.0%). Scanning electron microscopy revealed a porous, interconnected structure, while FTIR and XRD confirmed polymer interactions and a predominantly amorphous matrix. The encapsulated formulation maintained 8.0 × 10⁷ CFU g⁻¹ bead after 45 days of storage and provided sustained availability of viable propagules in soil. Its plant growth-promoting performance was evaluated in Capsicum annuum under pot conditions and compared with Trichoderma slurry and untreated controls. At 30 days, encapsulated treatment increased plant height, leaf number, leaf area, and dry biomass to 72.3 ± 3.0 cm, 98.4 ± 3.4, 56.8 ± 2.7 cm², and 18.9 ± 0.5 g, respectively. It also improved chlorophyll and carotenoid contents and enhanced antioxidant defense. At 10 days, SOD, APX, GPX, and CAT activities increased by 36.4%, 73.0%, 72.2%, and 54.9%, respectively, relative to the untreated control, while APX showed a 149.5% increase at 30 days. Overall, the hydrogel supported fungal survival and sustained delivery while promoting plant growth and reducing oxidative stress, demonstrating its potential as an eco-friendly delivery platform for Trichoderma-based bioinoculants in sustainable agriculture.