Biodiversity analysis of penicillium nalgiovense strains using ir spectroscopy and statistical methodology

MOAVRO, ALFONSINA; DELGADO, JUAN FRANCISCO; CASTELL, MELINA CECILIA; WAGNER, JORGE RICARDO; LUDEMANN, VANESA

Mar del Plata

Congreso; XVI Congreso Argentino de Ciencia y Tecnología de Alimentos; 2017

Asociación Argentina de Tecnólogos Alimentarios - AATA

Penicillium nalgiovense is a well-known fungal specie in meat industry due to its technological application in dry-cured products like salami. P. nalgiovense is characterized by showing phenotypic differences depending on the media on which it grows dividing it into six biotypes based on colony diameters, color and degree of conidia formation. Different techniques were used to observe biodiversity based on the amplification of polymorphic regions of DNA with specific primers as ISSR and RAPD assays.Infrared spectroscopy (IR) is a technique employed to characterize compounds from their functional groups. It is a promising method to identify filamentous fungi due to its easy sample preparation procedure, its short analysis time and the reliability of the data obtained. On the other hand, its utilization needs a representative extraction of fungi components and complex statistical methodology for data interpretation.The objective of this work was to evaluate the suitability of IR technique to differentiate nine selected P. nalgiovense strains, previously isolated from handmade salami of Colonia Caroya (Córdoba) and Tandil (Buenos Aires). A commercial starter (Mold 600, C. Hansen, Denmark) was included in the analyses. Fungi biomass was obtained from culture in PDA (Potato Dextrose Agar) and subsequent growth in YES (Yeast Extract Sacarose) liquid media (25 ºC, 130 rpm, at least 48 h). Ultrasonic homogenization (10 min) and centrifugation (15 min, 12000 rpm, 4 ºC) were used to dissociate each culture in order to obtain the mycelia pellet for FTIR analysis. It was resuspended in 10 mL of distilled water. 0.5 - 1 mL of each suspension were placed in a ZnSe plate and dried with hot air. A Fourier Transform IR spectrometer (IR-Affinity, Shimadzu, Japan) was used to conduct measures by three times in triplicates. The acquisition parameters were 64 scans, spectral resolution of 4.0 cm-1 in the range of 4000 to 400 cm-1 wavenumber. Thirty-two most representative peaks were used to conduct a Principal Components Analysis (R 3.2.3, R Foundation for Statistical Software) and a final clustering with Ward´s algorithm. The dendrogram obtained has demonstrated that it was not possible to differentiate the two biotypes of P. nalgiovense tested, under extraction conditions and selection criteria of peaks used. However, the strain obtained from Tandil salami was satisfactory discriminated with respect to Colonia Caroya?s strains. From results obtained, we conclude that IR technique offers reproducible data but biomass extraction is critical to group and differentiate strains. The suitability to identify a specific fingerprint enables IR technique to be a useful tool for identification of unknown filamentous fungi using spectral data references.