Formulation of Microbial Inoculants by Encapsulation in Natural Polysaccharides: Focus on Beneficial Properties of Carrier Additives and Derivatives

Abstract

In the last 10-15 years, the wide application of bioformulated plant beneficial microorganisms is accepted as an effective alternative of chemical agro-products. Two main problems can be distinguished in their production and application: (a) economical competiveness based on the overall upstream and downstream operational costs, and (b) development of commercial products with a high soil-plant colonization potential in controlled conditions but not able to effectively mobilize soil nutrients and/or combat plant pathogens in the field. To solve the above problems, microbe-based formulations produced by immobilization methods are gaining attention as they demonstrate a large number of advantages compared to other solid and liquid formulations. This mini-review summarizes the knowledge of additional compounds that form part of the bioformulations. The additives can exert economical, price-decreasing effects as bulking agents or direct effects improving microbial survival during storage and after introduction into soil with simultaneous beneficial effects on soil and plants. In some studies, combinations of additives are used with a complex impact, which improves the overall characteristics of the final products. Special attention is paid to polysaccharide carriers and their derivates, which play stimulatory role on plants but are less studied. The mini-review also focuses on the potential difficulty in evaluating the effects of complex bio-formulations.

Towards Better Understanding of the Interactions and Efficient Application of Plant Beneficial Prebiotics, Probiotics, Postbiotics and Synbiotics

“…When the probiotic microorganism is a Psolubilizing agent, the synbiotic mixture could additionally be enriched with plant available P (Shilev et al, 2019). Similar synbiotic characteristics can be observed in microbial inoculants encapsulated in natural gels in the presence of additives with beneficial microbial stimulating action (Vassilev et al, 2020).…”

“…The period of searching for easy to cultivate soil microorganisms, their characterization, and testing in controlled conditions was replaced by another one with studies on novel, more efficient and economic fermentation mode of production and formulations. Co-cultivation and formulation of compatible PBM and inclusion of various additives in the formulations become fundamental part of the overall production technology (Vassilev et al, 2014;Vassilev et al, 2015;Vassilev et al, 2020). Another, pivotal point of the new approach to understand and manage the functional and genetic role of soil microorganisms in the soil-plant systems, is the comparison between human gut microbiome and plant microbiome (Adam et al, 2016).…”

“…One of the most promising formulation techniques is the encapsulation in macro-and micro-beads of polysaccharides which guarantees a continuous deliver of the inoculant into soil preventing the effect of soil and environmental stress factors including indigenous microbial community (Bashan et al, 2016;Qiu et al, 2019). However, a simple gel-entrapment is not sufficient to ensure economical advantages and desired agronomic impact of the formulates (Vassilev et al, 2020). Double/multiple inoculants combined with biostimulants and other additives including seeds (all-in-one smart bio-formulates) should be developed to complete with the traditional chemical fertilizers (Vassilev et al, 2015;Trivedi et al, 2017).…”

“…Which are the risks of using microorganisms in soil–plant systems? Wrong formulation procedures without osmoprotectants, UV-protectors, fillers with nutrient value, and other plant benefiting additives usually provoke inconsistent results under field conditions ( Bashan et al., 2016 ; Vassilev et al., 2020 ). Further risks include various abiotic and biotic factors, which affect the rate of microbial colonization, the presence of other, more competent, components of the microbial population, the level of plant needs and capacity to attract and feed beneficial microorganism ( Fierer, 2017 ).…”

Microbiome Innovation in Agriculture: Development of Microbial Based Tools for Insect Pest Management

“…Murthy et al (2014) demonstrated that larvae subjected to Bt nanoparticles resulted in a faster and higher mortality as compared to unhomogenized Bt powder, owing to increased solubility of the Cry toxin in the alkaline midguts. Additionally, the development of nanoformulation delivery systems, such as nanoemulsion, nanocapsule, and nanosuspension, enhances the durability and stability of biopesticides under variable environmental conditions including exposure to UV light and humidity (Li et al, 2015;Sabbour and Singer, 2016;Zhang et al, 2016;Damalas and Koutroubas, 2018;Vassilev et al, 2020). These delivery systems are ecofriendly since they are often made of biodegradable natural polymers.…”