Development of Starch–Alginate–PVA Hydrogel Beads for Encapsulation and Sustained Delivery of Trichoderma longibrachiatum in Capsicum annuum

The development of sustainable microbial delivery systems is essential for improving the efficiency and stability of bioinoculants in agricultural applications. In the present study, a biodegradable sodium alginate–starch–polyvinyl alcohol (PVA) hydrogel system was developed for encapsulation of Trichoderma longibrachiatum using the ionic gelation method. The prepared hydrogel beads were characterized for their physicochemical, morphological, and structural properties to evaluate their suitability as controlled-release carriers for fungal bioinoculants. The encapsulated beads exhibited uniform spherical morphology, high moisture retention, enhanced swelling behavior, and high encapsulation efficiency. Scanning electron microscopy revealed porous and interconnected surface architecture favorable for water diffusion and gradual microbial release. FTIR and XRD analyses confirmed successful polymer blending, intermolecular interactions, and the predominantly amorphous nature of the hydrogel matrix.The encapsulated formulation maintained high fungal viability during storage and demonstrated sustained release of viable propagules into soil over time. The plant growth-promoting efficacy of the encapsulated Trichoderma formulation was evaluated using Capsicum annuum under pot culture conditions and compared with slurry and untreated control treatments. Plants treated with encapsulated hydrogel beads showed significant improvement in morphological parameters, including plant height, leaf number, leaf area, and biomass accumulation. Enhanced stomatal characteristics and increased chlorophyll and carotenoid contents indicated improved photosynthetic performance in treated plants. In addition, encapsulated Trichoderma significantly reduced reactive oxygen species and lipid peroxidation while enhancing antioxidant enzyme activities, including superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase. The reduction in oxidative stress was accompanied by increased protein accumulation and improved physiological stability. The results demonstrate that the sodium alginate–starch–PVA hydrogel system provides an efficient and eco-friendly platform for sustained delivery of Trichoderma inoculants. The synergistic interaction between the biodegradable polymer matrix and fungal bioinoculant improved microbial survival, controlled release behavior, antioxidant defense, and plant growth promotion, highlighting its potential application in sustainable agriculture and environmentally friendly crop production systems.