Evaluation of Suitable Polymers for the Development of High-Concentrated Liquid Biofertilizers

An improvement in the present liquid formulation of biofertilizer is essential to expand its shelf life and enhance the bioefficacy potential of the inoculated crops. Here, we screened ten different water-soluble polymers for their feasibility as cell protectants in liquid biofertilizers for the duration of three months. The physio-chemical properties and Escherichia coli survival assay experiments identified five potential polymers: hydroxypropyl methylcellulose, polyvinyl alcohol, and natural polymers extracted from seaweed, red algae, and brown algae. These five polymers' aqueous solutions comply with the standard parameters of liquid biofertilizers. Further, these polymers were compared with standard liquid biofertilizer diluting medium (phosphate buffer with glycerol) for the shelf life of two biofertilizer strains, viz., Azospirillum lipoferum (Az204) and Bacillus megaterium var. phosphaticum (Pb1). All the polymers had high cell viability up to 60 days after incubation. In conclusion, the results suggest that these polymers could be effective encapsulating agents to improve the quality of liquid biofertilizers.