Source: Juan. C. Sanchez-Hernandez and J. Domínguez (2017). Vermicompost derived from spent coffee grounds: assessing the potential for enzymatic ...
Solid vermicompost
Pesticide Treatment
Liquid vermicompost
Clays
Pesticide
2 3
Surfactants
Microorganisms
5 Humic material
4 Organic matter
Enhanced bioaccessibility
EE Extracellular detoxification
Biostimulation-induced bioremediation by vermicompost
Pesticide bound to organo-mineral complexes
1
6
A conceptual scheme illustrating how vermicompost may contribute to pesticide degradation and transformation in soil. Briefly, binding of OP pesticides to organic matter in vermicompost (step 1 in the Figure) would be the main route whereby vermicompost reduces pesticide transport and toxicity. Likewise, as an organic amendment, vermicompost has a biostimulation effect in soil microbes (step 2). Enhanced microbial activity and biomass has two effects on pesticide bioavailability and biodegradation: 1) pesticides initially sorbed on clay and soil organic matter may be desorbed by the action of surfactants produced by microorganisms (e.g., glycolipids, phospholipids, lipopeptides, lipoproteins and lipopolysaccharides) (step 3); 2) microbes may also directly attack sorbed pesticides through exoenzymes that they release. Therefore, surfactants facilitate the bioavailability of pesticides (step 4) for subsequent degradation by proliferating microorganisms (step 5) and for transformation or breakdown by the action of extracellular detoxifying enzymes (e.g., carboxylesterases, laccases and peroxidases) associated with the organic matter in vermicompost (step 6). Although it is still early to draw firm conclusions, preliminary data by our research group support the idea that extracellular enzymes (EE) such as carboxylesterases (EC 3.1.1.1) present in spent coffee ground- and grape marc-derived vermicomposts may act as molecular scavengers of organophosphate (OP) pesticides. Source: Juan C. Sanchez-Hernandez and J. Domínguez (2017). Vermicompost derived from spent coffee grounds: assessing the potential for enzymatic bioremediation, In: Charis M. Galanakis (Ed.), Handbook of Coffee Processing By-Products, Elsevier (in press). Scheme elaborated by Juan C. Sanchez-Hernandez.
