Abstract:This is the first study to provide ways of maintaining viability of PsJN during desiccation stress and to investigate the applicability of its EPS as a protectant, thus ultimately facilitating successful plant inoculation especially under field conditions.
“…Evaluating a formulation regarding its viability during air‐drying is therefore highly relevant. Indeed, it has been reported that protectants working well for one drying method are not always suitable for another – as shown when developing dry formulations for P. phytofirmans (Berninger et al ., ). In this case, gum arabic and yeast extract maintained high survival rates during freeze‐drying, but not during air‐drying, whereas the opposite was true for mannitol.…”
Section: The Drying Processmentioning
confidence: 97%
“…Particularly for non‐sporulating bacteria, which do not display the ability to adopt a highly resistant, dormant form to outlast adverse environmental conditions, desiccation is a physiologically challenging process (Potts, ). In extremely sensitive organisms, such as the endophytic plant growth‐promoting bacterium P. phytofirmans , desiccation coincided with a reduction in viability by six orders of magnitude (Berninger et al ., ). The damages resulting from desiccation partly depend on the drying method used, but are generally based on three main deleterious processes: oxidative damage, phase transition and browning reactions (García, ).…”
Section: Desiccation Damage and Protective Strategiesmentioning
confidence: 97%
“…It was shown to provide protection against desiccation and metal ion stress in several environmental strains (Ferreira et al ., ), which makes it a prospective protectant in formulation development. In fact, EPS improved viability of P. phytofirmans during air‐drying by up to six orders of magnitude compared with the control (Berninger et al ., ).…”
Section: Desiccation Damage and Protective Strategiesmentioning
confidence: 97%
“…Similar observations were made by Berninger et al . () when air‐drying P. phytofirmans in a zeolite matrix, where survival was lower than in osmoprotectants only.…”
SummaryThe application of beneficial, plant‐associated microorganisms is a sustainable approach to improving crop performance in agriculture. However, microbial inoculants are often susceptible to prolonged periods of storage and deleterious environmental factors, which negatively impact their viability and ultimately limit efficacy in the field. This particularly concerns non‐sporulating bacteria. To overcome this challenge, the availability of protective formulations is crucial. Numerous parameters influence the viability of microbial cells, with drying procedures generally being among the most critical ones. Thus, technological advances to attenuate the desiccation stress imposed on living cells are key to successful formulation development. In this review, we discuss the core aspects important to consider when aiming at high cell viability of non‐sporulating bacteria to be applied as microbial inoculants in agriculture. We elaborate the suitability of commonly applied drying methods (freeze‐drying, vacuum‐drying, spray‐drying, fluidized bed‐drying, air‐drying) and potential measures to prevent cell damage from desiccation (externally applied protectants, stress pre‐conditioning, triggering of exopolysaccharide secretion, ‘helper’ strains). Furthermore, we point out methods for assessing bacterial viability, such as colony counting, spectrophotometry, microcalorimetry, flow cytometry and viability qPCR. Choosing appropriate technologies for maintenance of cell viability and evaluation thereof will render formulation development more efficient. This in turn will aid in utilizing the vast potential of promising, plant beneficial bacteria as sustainable alternatives to standard agrochemicals.
“…Evaluating a formulation regarding its viability during air‐drying is therefore highly relevant. Indeed, it has been reported that protectants working well for one drying method are not always suitable for another – as shown when developing dry formulations for P. phytofirmans (Berninger et al ., ). In this case, gum arabic and yeast extract maintained high survival rates during freeze‐drying, but not during air‐drying, whereas the opposite was true for mannitol.…”
Section: The Drying Processmentioning
confidence: 97%
“…Particularly for non‐sporulating bacteria, which do not display the ability to adopt a highly resistant, dormant form to outlast adverse environmental conditions, desiccation is a physiologically challenging process (Potts, ). In extremely sensitive organisms, such as the endophytic plant growth‐promoting bacterium P. phytofirmans , desiccation coincided with a reduction in viability by six orders of magnitude (Berninger et al ., ). The damages resulting from desiccation partly depend on the drying method used, but are generally based on three main deleterious processes: oxidative damage, phase transition and browning reactions (García, ).…”
Section: Desiccation Damage and Protective Strategiesmentioning
confidence: 97%
“…It was shown to provide protection against desiccation and metal ion stress in several environmental strains (Ferreira et al ., ), which makes it a prospective protectant in formulation development. In fact, EPS improved viability of P. phytofirmans during air‐drying by up to six orders of magnitude compared with the control (Berninger et al ., ).…”
Section: Desiccation Damage and Protective Strategiesmentioning
confidence: 97%
“…Similar observations were made by Berninger et al . () when air‐drying P. phytofirmans in a zeolite matrix, where survival was lower than in osmoprotectants only.…”
SummaryThe application of beneficial, plant‐associated microorganisms is a sustainable approach to improving crop performance in agriculture. However, microbial inoculants are often susceptible to prolonged periods of storage and deleterious environmental factors, which negatively impact their viability and ultimately limit efficacy in the field. This particularly concerns non‐sporulating bacteria. To overcome this challenge, the availability of protective formulations is crucial. Numerous parameters influence the viability of microbial cells, with drying procedures generally being among the most critical ones. Thus, technological advances to attenuate the desiccation stress imposed on living cells are key to successful formulation development. In this review, we discuss the core aspects important to consider when aiming at high cell viability of non‐sporulating bacteria to be applied as microbial inoculants in agriculture. We elaborate the suitability of commonly applied drying methods (freeze‐drying, vacuum‐drying, spray‐drying, fluidized bed‐drying, air‐drying) and potential measures to prevent cell damage from desiccation (externally applied protectants, stress pre‐conditioning, triggering of exopolysaccharide secretion, ‘helper’ strains). Furthermore, we point out methods for assessing bacterial viability, such as colony counting, spectrophotometry, microcalorimetry, flow cytometry and viability qPCR. Choosing appropriate technologies for maintenance of cell viability and evaluation thereof will render formulation development more efficient. This in turn will aid in utilizing the vast potential of promising, plant beneficial bacteria as sustainable alternatives to standard agrochemicals.
“…3 ). Formulation can be solid-based or liquid, the former further can be either dry or wet as per the requirement ( Berninger et al, 2017 ; Oliveira et al, 2017 ; Berger et al, 2018 ). Fig.…”
Section: Commercial Biofertilizers: Preparation and Applicationmentioning
Highlights
Agriculture plays an important role in a country's economy. In modern intensive agricultural practices, chemical fertilizers and pesticides are applied on large scale to increase crop production in order to meet the nutritional requirements of the ever-increasing world population. However, rapid urbanization with shrinking agricultural lands, dramatic change in climatic conditions and extensive use of agrochemicals in agricultural practices has been found to cause environmental disturbances and public health hazards affecting food security and sustainability in agriculture. Besides this, agriculture soils are continuously losing their quality and physical properties as well as their chemical (imbalance of nutrients) and biological health due to indiscriminate use of agrochemicals. Plant-associated microbes with their plant growth- promoting traits have enormous potential to solve these challenges and play a crucial role in enhancing plant biomass and crop yield under greenhouse and field conditions. The beneficial mechanisms of plant growth improvement include enhanced availability of nutrients (i.e., N, P, K, Zn and S), phytohormone modulation, biocontrol of phytopathogens and amelioration of biotic and abiotic stresses. This plant-microbe interplay is indispensable for sustainable agriculture and these microbes may perform essential role as an ecological engineer to reduce the use of chemical fertilizers. Various steps involved for production of solid-based or liquid biofertilizer formulation include inoculum preparation, addition of cell protectants such as glycerol, lactose, starch, a good carrier material, proper packaging and best delivery methods. In addition, recent developments of formulation include entrapment/microencapsulation, nano-immobilization of microbial bioinoculants and biofilm-based biofertilizers. Thus, inoculation with beneficial microbes has emerged as an innovative eco-friendly technology to feed global population with available resources. This review critically examines the current state-of-art on use of microbial strains as biofertilizers in different crop systems for sustainable agriculture and in maintaining soil fertility and enhancing crop productivity. It is believed that acquisition of advanced knowledge of plant-PGPR interactions, bioengineering of microbial communities to improve the performance of biofertilizers under field conditions, will help in devising strategies for sustainable, environment-friendly and climate smart agricultural technologies to deliver short and long terms solutions for improving crop productivity to feed the world in a more sustainable manner.
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