Electrospun Microbial-Encapsulated Composite-Based Plasticized Seed Coat for Rhizosphere Stabilization and Sustainable Production of Canola (Brassica napus L.)

Abstract

Plant-growth-promoting bacteria show promises in crop production; nevertheless, innovation in their stable delivery is required for practical use by farmers. Herein, the composite of poly­(vinyl alcohol)/poly­(vinylpyrrolidone) plasticized with glycerol and loaded with the microbial consortium (Bacillus subtilis plus Seratia marcescens) was fabricated and engineered onto canola (Brassica napus L.) seed via electrospinning. Scanning electron microscopy showed that the biocomposite is a one-dimensional membrane, which encapsulated microbes in a multilayered nanostructure, and their interfacial behavior between microorganism and seed is beneficial for safer farming. A universal testing machine and thermogravimetric analysis demonstrated that the biocomposite holds sufficient thermomechanical properties for stable handling and practical management. A spectroscopic study resolved the living hybrid–polymer structure of the biocomposite and proved the plasticizing role of glycerol. A swelling study supports the degradation of the biocomposite in the hydrophilic environment as a result of the leaching of the plasticizer, which is important for the sustained release of microbial cells. A shelf life study supported that the biocomposite seed coat placed a threshold level of microbes [5.675 ± 0.48 log10 colony forming units (CFU)/seed] and maintained their satisfactory viability for 15 days at room temperature. An antifungal and nutrient-solubilizing study supported that the biocomposite seed coat could provide opportunities to biocontrol diseases and improve nutrient acquisition by the plant. A pot study documents the better performance of the biocomposite seed coat on seed germination, seedling growth, leaf area, plant dry biomass, and root system. A chemical and microbial study demonstrated that the biocomposite seed coat improved the effectiveness of the bioinoculant in the root–soil interface, where they survive, flourish, and increase the nutrient pool status. In particular, this study presents advances in the fabrication of the biocomposite for encapsulation, preservation, sustained release, and efficacious use of microorganisms onto seeds for precision farming.

Applications, challenges, and needs for employing synthetic biology beyond the lab

“…Bio-polymer interfacing can also yield enhancement of PGPR delivery to crops. With the goal of enhancing organism stability and ease of PGPR delivery by farmers, Hussain et al 151 developed electrospun biocomposite polymer nanofibers for seed coating containing a B. subtilis and Seratia marcescens consortium developed to deliver multifaceted plant-growth-promoting activities while minimizing plant stress associated with inoculation of a single bacteria species. The seed coatings enabled encapsulation, preservation, and sustained release of plant-growth-promoting bacteria.…”

Recent advances in biodegradable matrices for active ingredient release in crop protection: Towards attaining sustainability in agriculture

“…To overcome the limitations of conventional seed coatings, other approaches have been explored such as the use of laboratory mixers, seed molding [ 21 , 52 ], and more recently electrospun nanofibers [ 14 , 40 , 53 , 54 , 55 ]. Electrospinning is a technique based on the application of electrical force to produce polymer nanofibers ranging from a few nanometers to several micrometers in diameter [ 56 , 57 ].…”

“…Because nonwoven nanofiber mats facilitate gas and moisture exchange when compared to traditional film coatings, Hussain et al. [ 54 ] exploited these properties to coat canola seeds with PVA and poly(vinylpyrrolidone) (PVP) composite nanofibers plasticized with glycerol containing a microbial consortium. Their study demonstrates an improved root system, plant germination, and effectiveness of the bioinoculant at the root–soil surface.…”

Immobilization of beneficial microbe Methylobacterium aminovorans in electrospun nanofibre as potential seed coatings for improving germination and growth of groundnut Arachis hypogaea

“…The high surface area to volume ratio and easy incorporation of active molecules has impelled researchers to investigate using electro spun nano bers in agricultural application such as nano sensors for pesticide residues detection (Ding et al 2009), protective clothing for farm labourers and agrochemical inputs (Lee and Lee 2012). Recently, seed invigoration with nano bres developed from various biodegradable polymers was explored as an alternate approach for smart delivery of inputs (Krishnamoorthy et al 2016; Krishnamoorthy and Rajiv 2017;Hussain et al 2019). Further, e-spun bre has been investigated as effective seed coating for localized and targeted delivery of inputs for improving germination and seedling growth of rice (Castaneda et al 2014), black gram (Raja et al 2020) and groundnut (Raja et al 2020;Raja et al 2017), and also for pathogen control in soyabean (Farias et al 2019).…”