Abstract

Immobilizarion of PGPR for agricultural applications aims to provide temporary physical protection from stressful environmental conditions and the gradual release of cells for successful root colonization, release the cells gradually. In this work, we immobilized Bradyrhizobium sp. SEMIA6144 or Azospirillum brasilense Az39 cells in 2% alginate beads prepared by ionic gelation process, and then stored up to 12 months at 4 °C. Alginate matrix showed interaction with the immobilized bacteria (FTIR), allowed a constant release of cells, and improved their viability and capability to interact with Arachis hypogaea. Cell number into beads reached 10⁷ CFU.bead⁻¹; however, viability decreased from 4 months of storage for Az39, while it was maintained up to 12 months for SEMIA6144, showing a low metabolic activity measured by the MTT assay. Adhesion of SEMIA6144 and Az39 from new beads to peanut root was 11.5% and 16%, respectively, higher than non-immobilized bacteria. Peanut inoculation with 12 months storage SEMIA6144 beads significantly increased root length and biomass at 30 days of growth, and under restrictive water condition (RWC), nodulation and total plant N content increased compared with liquid inoculation. Our results demonstrate that immobilization of SEMIA6144 and Az39 in alginate matrix is a potential alternative to enhance peanut growth even under RWC.

Key points

• Alginate encapsulation enhances viability of SEMIA6144 or Az39 under storage at 4 °C for 1 year.

• Alginate beads 2% ensure the gradual release of the microorganisms.

• Cells from beads stored for long periods present chemotaxis and adhesion to peanut root.

• Peanut inoculation with 1-year-old SEMIA6144 beads improves nodulation and growth in RWC.

中文翻译：

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藻类基质中固定的根瘤菌和固氮螺菌可长期保存，可维持细胞活力并与花生相互作用

摘要

PGPR在农业上的固定化目的是提供暂时的物理保护，使其免受压力环境的影响，并逐渐释放细胞以成功根定居，并逐渐释放细胞。在这项工作中，我们固定了Bradyrhizobium sp。SEMIA6144或巴西固氮螺菌Az39细胞在2％藻酸盐珠粒制备通过离子凝胶化过程，然后存储长达12个月，在4℃。海藻酸盐基质显示出与固定细菌（FTIR）的相互作用，允许细胞不断释放，并提高了它们的活力和与花生的相互作用。成珠的细胞数达到10 ⁷ CFU.bead ^-1; 然而，Az39的活力从保存4个月开始下降，而SEMIA6144则保持了12个月，显示出通过MTT分析测得的低代谢活性。SEMIA6144和Az39从新珠子到花生根的粘附力分别比未固定化的细菌高11.5％和16％。花生接种有12个月的SEMIA6144珠子，可在生长30天时显着增加根长和生物量，并且在限制性水条件（RWC）下，与液体接种相比，结瘤和植物总氮含量增加。我们的结果表明，即使在RWC条件下，将SEMIA6144和Az39固定在藻酸盐基质中也是增强花生生长的潜在替代方法。

关键点

•海藻酸盐封装增强了SEMIA6144或Az39在4°C下储存1年的生存能力。

•2％的藻酸盐珠可确保微生物逐渐释放。

•长时间存放的珠子细胞具有趋化性并粘附于花生根。

•花生接种1岁的SEMIA6144磁珠可改善RWC中的结瘤和生长。