Effect of proteases on soil: Bioestimulation and Microbial Biodiversity

Proteins constitute the main source of nitrogen in soil organic matter. The utilization of this nitrogen is limited by the breakdown of proteins in peptides and free amino acids. Therefore, proteases have a relevant role in the use of protein N. The aim of this study is to assess the effect of exogenous microbial protease both on soil microbial biostimulation and on biodiversity. In addition to the protease, an insoluble-protein low-bioavailable substrate such as poultry feathers waste was added to enhance the effect of protease on soil. Protease, both on its own and in combination with poultry feathers, has shown a biostimulant effect on soil microbial activity that was reflected in both dehydrogenase and phosphatase activities. The DNA metabarcoding analysis also revealed specific changes in soil biodiversity mainly defined by the enrichment in plant-growth promoter microorganisms, mainly those producers of hydrolase enzymes such as phosphatase and ammonifiers. Thus, the present work supports the use of proteases for fertilizer purposes and values the recycling of keratinous industrial wastes in the field of biofertilization.