Composting operation systems are valuable sources of microorganisms and enzymes. This work reports the assessment of proteolytic enzymes from cultivable bacteria isolated from a composting facility of the Sao Paulo Zoo Park (SPZPF), Sao Paulo, Brazil. Three hundred bacterial isolates were obtained and identified based on 16S rRNA gene as belonging to 13 different genera. The most common genus among the isolates was Bacillus (67%); some of which show high proteolytic activity in their culture media. Biochemical assays of hydrolytic activities using FRET peptides as substrates allowed the characterization of a repertoire of serine proteases and metalloproteases with different molecular weights secreted by Bacillus strains isolated from composting. Furthermore, thermostable serine and metalloproteases were detected in the composting leachate, which might be of interest for industrial applications.
This work aims to evaluate the potential of an organic compost in providing nutrients when added to the soil. This fertilizer is generated in a production unit located in the São Paulo Zoo Park in Brazil. It comprises animalmanure, plants pruning, dead trees, and solidwaste from water treatment and sanitary effluents. This compost’s growth power, which is efficiently used to fertilize the garden and farm of the zoo, was assessed. Six soil treatments were chemically characterized and tested in the cultivation of lettuce (Lactuca sativa L.). The nutrient (N, P, K, S, Ca, Mg, Na, Cu, Fe, Mg, and Zn) contents in the lettuce and soils were evaluated using chemometrics. The soil fertility analysis showed an increase in the quality of the composted soil due to Mg and Fe and pH increase. Principal component analysis showed that Al was a relevant nutrient for all treatments before planting, whereas soil with mineral fertilizer or leachate contained high levels of Cu. Samples of compost-enriched soil exhibited high concentrations of Fe and Mg before planting. Cationexchange capacity, H+Al, P, K, S, and pH allowed the treatments’ comparison. The loadings plot showed that compost-enriched soil samples were characterized by K, Mg, Cu, S, and P; and leachate-enriched soil by Fe, Mg, and Na. Lettuce’s elemental analysis exhibits a direct correlation between the soil conditions and the quality of the vegetable produced. Compost-enriched soil produced larger plants yielding average weight leaves of around 3 to 10 times higher than all the other treatments, indicating its benefits for soil fertilization. This recycling process is a sustainable development tool that allows the reuse of waste produced in zoos worldwide.