Heidi Schalchli

Antifungal activity of volatile metabolites emitted by mycelial cultures of saprophytic fungi

The antifungal activity of molecular identified Chilean saprobiontic fungi, Trichoderma viride, Schizophyllum commune and Trametes versicolor, on the fungal plant pathogens Botrytis cinerea and Fusarium oxysporum, and the saprotrophic mould Mucor miehei was investigated using two types of inhibition bioassay: (1) bi-compartmented Petri dishes and (2) two Erlenmeyer flasks connected by their upper parts. The chemical composition of volatile organic compounds (VOCs) released by saprobiontic fungi was also investigated using headspace solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC-MS) analysis. Of the saprobiontic fungi evaluated, one isolate of S. commune showed the highest inhibitory activity against B. cinerea and M. miehei, 86.0±5.4 and 99.5±0.5% respectively. The volatile profiles of fungal isolates were shown to contain a different class of compounds. The major components in the headspace of mycelial cultures were 6-pentyl-α -pyrone (T. viride), ethanol and β -bisabolol (S. commune), and a sesquiterpene alcohol (Tr. versicolor). This is the first study reported on the release of VOCs by Chilean native fungi and their antifungal activity wrt. plant pathogenic fungi.

The antioxidant properties of calafate (Berberis microphylla) fruits from four different locations in southern Chile

Se determino la capacidad antioxidante (CA), antocianinas totales (AT) y fenoles totales (FT) de frutos de calafate de cuatro localidades del sur de Chile (El Blanco, Lonquimay, Manihuales y Temuco) utilizando los metodos del radical libre 2,2-difenil -1- picrilhidrazil (DPPH) y la capacidad de inhibir la oxidacion del acido linoleico, asi como pH diferencial y el metodo de Folin-Ciocalteu. Ademas, se identificaron los compuestos fenolicos por medio de HPLC-DAD (Cromatografia liquida de alta eficacia- con Deteccion por Arreglo de Diodos). Los resultados mostraron que los FT variaron significativamente segun la localidad, destacandose Manihuales con 34,9 mg GAE g-1 de fruta seca. La CA vario de acuerdo con la metodologia, por DPPH vario significativamente entre localidades, y de nuevo se destaco Manihuales con los valores mas altos de CA (9,4 mg de TE g-1 de frutas secas). La inhibicion de la oxidacion del acido linoleico revelo que no hubo diferencias significativas entre Temuco y El Blanco, presentando Manihuales el valor mas alto (0,25 mg de TE g-1 de fruta seca). Las AT mostraron diferencias significativas entre localidades, siendo El Blanco el mayor (0,64 mg de cianidina g-1 fruta seca). En relacion a los compuestos fenolicos, fueron identificados acido galico, acido clorogenico, acido cafeico, acido cumarico, acido ferulico, y flavonoides como rutina, miricetina, quercetina y kaempferol. Estos compuestos variaron de acuerdo a la localidad: Temuco mostro un valor mas alto de acido cumarico; Lonquimay en acido clorogenico, acido cafeico, acido cumarico, y flavonoides como rutina y quercetina; Manihuales en acido galico, acido clorogenico, acido cafeico, acido ferulico y favonoides como la rutina y la quercetina; El Blanco en acido cafeico y flavonoides como miricetina, quercetina y kaempferol. La CA se correlaciono positivamente con FT (DPPH r=1; acido linoleico r=0,84). Por el contrario, se obtuvo una baja correlacion entre la CA y AT (DPPH r=0,31; acido linoleico r=-0,28), y entre FT y AT (r=0,27). Se concluye que los frutos de calafate de diferentes areas geograficas del sur de Chile tienen diferencias estadisticamente significativas en su CA, FT, AT y compuestos fenolicos, siendo Manihuales el area que presento los valores mas altos para estos parametros. La composicion quimica de los frutos tambien vario dependiendo del origen de las muestras.

Volatiles from white-rot fungi for controlling plant pathogenic fungi

Fungal volatile secondary metabolites play important roles in mediating antagonistic and beneficial interactions among organisms. The effects of eight strains of white-rot fungi cultured on potato waste against the mycelial growth of Botrytis cinerea, Fusarium oxysporum and Mucor miehei were investigated using a bi-compartmented Petri dish assay. The chemical composition of volatile organic compounds released from the strain with the highest inhibitory effect was also investigated by headspace solid-phase microextraction and gas chromatography/mass spectrometry analysis. Of the eight white-rot fungi evaluated, Anthracophyllum discolor. Sp4 showed a high inhibitory activity against M. miehei (approximately 76%) and B. cinerea (approximately 20%). F. oxysporum was inhibited to a lesser extent (approximately 10%) by A. discolor and T. versiscolor. The gas chromatography/mass spectrometry analysis showed nine main volatile compounds released from A. discolor Sp4, among them are the sesquiterpenesα-bisabolene and bulnesene, and the chlorinated aromatic compounds 1,5-dichloro-2,3-dimethoxybenzene, 3,5-dichloro-4-methoxybenzaldehyde and 3-chloro-4-methoxybenzaldehyde. Some of which have been reported previously with antimicrobial activity. The antifungal activity and volatile profile of A. discolor have not been previously reported.

Production of ligninolytic enzymes and some diffusible antifungal compounds by white-rot fungi using potato solid wastes as the sole nutrient source

The aim of this study was to evaluate the synthesis of ligninolytic enzymes and some diffusible antifungal compounds by white‐rot fungi (WRF) using peels or discarded potato as the sole nutrient source.

Sequential white-rot and brown-rot fungal pretreatment of wheat straw as a promising alternative for complementary mild treatments

White-rot and brown-rot fungi have complementary mechanisms to selectively degrade lignin and holocellullose, respectively. Thereby, a fungal co-culture of a white-rot and a brown-rot fungal could result in efficient strategy for a mild lignocellulosic biomass pretreatment. In this work, single, sequential and co-inoculation of the selective-lignin degrading white-rot fungus Ganoderma lobatum and the brown-rot fungus Gloeophyllum trabeum were evaluated as biological pretreatments of wheat straw to enhance enzymatic hydrolysis of cellulose. The single cultures of G. lobatum and G. trabeum exhibited preferential degradation of lignin and hemicellulose, respectively. The total crystallinity index decreased in samples pretreated with G. trabeum but not with G. lobatum. The pretreatment with single cultures of G. lobatum or G. trabeum increased glucose yields by 43.6% and 26.1% respectively compared to untreated straw. Although co-inoculation resulted in higher yields of glucose when compared with single cultures, only a slight synergistic effect between fungi was observed. Contrary, the sequential inoculation of G. lobatum incubated for 10 days followed by G. trabeum incubated for 10 days more showed a strong synergic effect on enzymatic hydrolysis. This sequential culture showed the highest glucose yield (191.5 mg g-1 wheat straw), 2.8-fold higher than untreated wheat straw, and 140-150% higher than the single-cultures of G. lobatum and G. trabeum, respectively.