Métodos de preservação de fungos potencialmente toxicogênicos

Abstract

Microorganisms are a source of many high-value compounds which are useful to every living being, such as humans, plants and animals. Since the process of isolating and improving a microorganism can be lengthy and expensive, preserving the obtained characteristic is of paramount importance, so the process does not need to be repeated. Fungi are eukaryotic, achlorophyllous, heterotrophic organisms, usually filamentous, absorb their food, can be either macro or microscopic, propagate themselves by means of spores and store glycogen as a source of storage. Fungi, while infesting food, may produce toxic substances such as mycotoxins. The great genetic diversity of the Kingdom Fungi renders relevant the preservation of fungal cultures for many years. Several international reference mycological culture collections are maintained in many countries. The methodologies that are most fit for preserving microorganisms for extended periods are based on lowering the metabolism until it reaches a stage of artificial numbness. The goal of this study was to analyze three methods for potentially toxigenic fungal conservation (Castellani´s, continuous passages and lyophilization) and to identify the best among them. Samples - unprocessed foods which presented signs of deterioration (pear, peach, Brazil nut and peanut) and processed foods still within expiration date (canned corn, linseed, raisin and peanut) - were obtained from the Lavras retail market. The fungi obtained from the samples were isolated and identified, and only the ones with toxigenic potential were selected, resulting a total of 12 fungi of the genera Aspergillus and Penicillium. The isolated ones were submitted to three methods for fungal conservation (Castellani, continuous passages and lyophilization) and evaluated every two months during eight months, which presented a 100% viability in all three methods. The conservation of the toxin production, however, varied by method.