Vinasse waste from sugarcane-based bioethanol production plants kills Moniliophthora Perniciosa, the causative agent of cacao witches' broom disease

Abstract

Bioethanol production based on sugarcane juice fermentation yields vinasse, a dark, dense liquid waste high in potassium. In Brazil, one of the world’s biggest bioethanol producer, vinasse is used for fertirrigation of the sugar-cane fields, replacing mineral soil amendments. Nevertheless, the production largely exceeds this application, prompting exacerbated usage, unduly long-term storage and even illegal dumping. Vinasse thus progressively became an environmental hazard, damaging soils and superficial and ground waters, adding a negative burden to a supposedly green-fuel industry. The solution resides in decreasing production yields and/or using it for yet other economically interesting applications. This work focuses on the latter. Vinasses from three bioethanol plants from Brazil were tested for their ability to contain the proliferation of Moniliophthora perniciosa, the aggressive filamentous fungus responsible for cacao Witches’ Broom Disease (WBD). This disease caused a severe economic fall-out in South American cacao producing regions, particularly seriously in Brazil. Immersing or spraying the mycelium with vinasse either kills the fungus or impedes its proliferation at varying time/dosage. Identically testing another genetically unrelated phytopathogen, showed this effect is not that of a generalized biocide/fungicide. Results suggest that vinasse could be used to contain/revert the prevalence of cacao’s WBD to manageable levels. Vinasse would thus shift from industrial waste with disposal-associated costs, to being a tool for the agronomic sustainability and revival of the South American regional cacao-dependent socio-economies.