Encapsulation in Trehalose-Supplemented Alginate Beads Maintains Bradyrhizobium Functionality and Mitigates Water Stress in Arachis hypogaea L.

Water stress is a major constraint on peanut (Arachis hypogaea L.) production, as it limits plant growth and biological nitrogen fixation. The development of long-lasting microbial inoculants is a key strategy for mitigating these effects. This study investigated whether the addition of trehalose improves the long-term functionality of Bradyrhizobium sp. SEMIA 6144 when encapsulated in alginate beads, and how this influences peanut yield under water stress conditions. Encapsulated bacteria, with and without trehalose, were stored for 12 months, and their ability to interact with plants at an early stage and promote plant growth was examined. Storage increased bacterial motility and aggregation, while biofilm formation remained stable. Trehalose supplementation significantly enhanced root adhesion, increasing bacterial colonization by approximately 105%. In pot experiments, inoculation with the encapsulated bacteria improved plant growth and nodulation under stress conditions. Plants inoculated with fresh beads exhibited increases in shoot length of up to 24%, maintaining higher biomass than uninoculated controls. Encapsulated formulations also mitigated the effects of drought on nodulation and physiological parameters. Overall, trehalose-enriched alginate encapsulation preserves bacterial functionality during long-term storage and enhances plant–microbe interactions, thereby improving peanut resilience under water stress and offering a promising strategy for the development of sustainable bioinoculants.