In this study, konjac glucomannan (KG) was incorporated in high acyl gellan (HAG) and low acyl gellan (LAG) hydrogels in different ratios. The addition of KG increased pseudoplasticity and thermal hysteresis values of the hydrogels. Improvement in elasticity and water holding capacity (WHC) was observed in KG -LAG hydrogels. The highest WHC (98.5 %) was observed for 1K1H (KG:HAG = 1:1) and 3K7L (KG:LAG = 3:7) hydrogels. The crystallinity of the composite hydrogels was lower than hydrogels prepared from individual biopolymers. The hydrogels exhibited a rough surface with minute pores in the cross-section, due to the aggregation of glucomannan on the gellan network in the composite hydrogels. While HAG and 1K1H hydrogels exhibited greater swelling at low pH (3.0), LAG and 3K7L exhibited greater swelling at high pH (11.0). At pH 7.0, the hydrogels exhibited swelling indices >300 %. Incorporation of 1K1H hydrogel at 10 % (w/w) in sandy loamy soil under semi -arid conditions increased the germination of fenugreek microgreens from 60 % to 80 % on the 15th day. Furthermore, the moisture evaporation rate of the soil reduced from 35 % to <15 %, positively impacting the physicochemical properties of the microgreens. The composite hydrogels were successful in achieving a controlled release of phosphate fertilizer.

Iodine deficiency is a global public health problem and dietary microgreens represent a possible cost-effective supplement. Bacillus velezensis is a commonly occurring soil bacteria that promotes plant growth. However, little attention has been paid to the effects of B. velezensis on the absorption of iodine by plants. Herein, we demonstrated that B. velezensis accelerates pepper seed germination and growth under 0.01 mmol/L KI supplement, with an 85.9% increase in fresh biomass. B. velezensis induced approximately 2.0 -fold higher iodine absorption. Likewise, colonization by B. velezensis occurred in the microgreens. Consequently, the total thiol, vitamin C, total phenolics, and the antioxidant capacity were increased. This was followed by a marked decrease in the catalase and total superoxide dismutase activities. Furthermore, the combination of B. velezensis and 0.01 mmol/L KI significantly decreased the relative water content and membrane damage (malondialdehyde and relative electrical conductivity). Intriguingly, the transcripts of ethylene biosynthesis genes CaACS10 and CaACO1 were downregulated, whereas CaACO3 expression was upregulated. Thus, the present study showed that B. velezensis accelerated iodine accumulation; improved seed germination and seedling growth; elicited antioxidant bioactivity; decreased membrane damage; and preserved vegetable microgreen quality during storage.