Native polymer degradation capacity of microorganisms in agricultural soils

Abstract

With a growing global population increasing demand for food production, fertilisers are of paramount importance in the agricultural industry. New fertiliser coating candidates may reduce environmental harm but it is critical that they are evaluated for their native biodegradation potential within agricultural soils and their effects on microbial communities. Four of the seven compounds tested, poly(1,4-butylene adipate) (PBA), polyethylene adipate (PEA), polycaprolactone (PCL) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), showed degradation by indigenous soil microorganisms with headspace CO₂ concentrations increasing between 14 to 98 % compared to the soil only control. Surprisingly, two previously characterised biodegradable polymers, polyethylene succinate (PES) and poly(1,4-butylene succinate) (PBS), showed minimal biodegradation in our study. Polymer degradation was confirmed visually using scanning electron microscopy and occurred in conjunction with shifts in the bacterial and fungal community composition of the soils. Soils with PBA, PEA, PCL and PHBV were enriched with polymer degrading microorganisms, such as Streptomyces spp., Bacillus spp., Exophiala spp. and Talaromyces spp. Using whole soil microcosms under ambient conditions to investigate indigenous degradation potential of polymers for fertiliser coatings provides an initial holistic picture of their degradation potential compared with using axenic cultures alone, and provides crucial new insights into the future of eco-friendly controlled release fertilisers.

Keywords: Agricultural management; Agricultural microbiomes; Biodegradation; Coated fertilisers; Polymers; Soil biology.