Optimization of the production of herbicidal toxins by the fungus Ascochyta caulina

• Published in: Biological control 2012-02, Vol.60 (2), p.192-198
• Main Authors: Vurro, M., Andolfi, A., Boari, A., Zonno, M.C., Caretto, S., Avolio, F., Evidente, A.
• Format: Article
• Language: English
• Subjects: Ascochyta; Ascochyta caulina; bioactive metabolites; bioactive properties; Biological control; Chenopodium album; Conidia; Fermentation; Fermentation production; Fermenters; Fungal phytotoxins; fungi; Growth conditions; Habitat; habitats; Herbicides; Inoculum; Liquid culture; Metabolites; Mycoherbicides; Natural herbicides; production costs; Purification; purification methods; Scaling; Toxins; weed control; Weeds; yeast extract
• ISSN: 1049-9644; 1090-2112
• DOI: 10.1016/j.biocontrol.2011.10.005

Ascaulitoxin, trans-aminoproline and ascaulitoxin aglycone (1, 2 and 3, respectively, left), three fungal metabolites with herbicidal properties, can be produced at a pre-industrial level by growing the fungus Ascochyta caulina in a fermentation unit and effectively purified as a mixture (right). [Display omitted] ► Production of natural metabolites with herbicidal properties by a liquid shaken fungal culture. ► Optimization of fungal growth and metabolite production. ► Minimization of costs of production. ► Set up of the conditions for production of the natural herbicide through a fermentation unit. Safer and more environmentally friendly methods, including the use of natural substances, would be favorably considered for weed management, particularly in those habitats where the use of chemicals is restricted or banned. Ascochyta caulina, a proposed mycoherbicide for biocontrol of the weed Chenopodium album, produces in liquid culture three main metabolites proposed as possible natural herbicides. Recently a research project, named ECO-VIA, initiated a series of studies aimed at developing the technologies to obtain a natural herbicide based on these bioactive metabolites. Particular attention was given to: maximizing toxin production; lowering the production costs; scaling up the production in fermentation systems; setting up a large scale purification method and identifying fast and inexpensive chemical methods to quantify toxins yields. The fungus proved to grow well and to produce up to 230mg of toxins l−1 culture when grown for 5–10days in shaken conditions, provided the initial inoculum was at least 105–106 conidia ml−1 of culture. Toxin production was improved by the addition of yeast extract to the medium. Given suitable inoculum and growth conditions, a stirred fermenter could be suitable for mass production of toxin.