Contaminantes microbianos en cervezas artesanales embotelladas de la Patagonia andina argentina / Microbial contaminants in bottled craft beer of Andean Patagonia, Argentina

Resumen La actividad cervecera en la Patagonia andina argentina tiene un rol muy importante en la economía de la región; una de las problemáticas que enfrenta, en términos de calidad, son las contaminaciones microbianas. La presencia de bacterias y levaduras contaminantes en la cerveza produce cambios microbiológicos, físicos y químicos, que impactan en sus atributos sensoriales. No obstante, pocas cervecerías establecen criterios y políticas que garanticen la calidad microbiológica de sus productos. El propósito de este trabajo fue estudiar por primera vez la incidencia de contaminantes microbianos en cervezas artesanales embotelladas producidas en la Patagonia andina argentina, además de identificar los principales microorganismos involucrados y determinar posibles relaciones entre los eventos de contaminación y variables fisicoquímicas de la cerveza. Para ello se analizaron 75 cervezas provenientes de 37 cervecerías de 12 localidades andinas. El 69,3% de las muestras analizadas evidenció crecimiento de microorganismos en los medios de cultivo empleados para la detección de contaminantes cerveceros. La bacteria Levilactobacillus brevis y levaduras del género Saccharomyces fueron los principales contaminantes identificados. Se comprobó que las contaminaciones microbianas impactaron sobre el perfil sensorial de la cerveza y que el cambio de pH fue un indicador de contaminación por bacterias lácticas. De cada 10 fábricas estudiadas, 8 presentaron problemas de contaminación, lo que pone en evidencia la necesidad de diseñar estrategias de prevención y control de contaminaciones en microcervecerías.

Abstract The brewing activity in Andean Patagonia plays a very important role in the region's economy, being microbial contamination one of the main problems in terms of quality. The presence of contaminant bacteria and wild yeasts in beer generate microbiological, physical and chemical changes that impact on its sensory attributes. However, few breweries establish criteria and policies to guarantee the quality of their products in a microbiological sense. The purpose of this work was to study for the first time the incidence of microbial contaminants in bottled craft beers from Andean Patagonia, identify the main microorganisms involved and establish relationships between contamination and the physicochemical variables of beer. We analyzed 75 beers from 37 breweries from 12 different Patagonian cities. Our results showed that 69.3% of the analyzed beer exhibited contaminant microorganism growth. Bacteria Levilactobacillus brevis and wild yeasts of Saccharomyces were the main microorganisms responsible for these contaminations. In addition, we found that microbial contamination had an impact on beer sensory profile and also that pH was correlated with the presence of lactic acid bacteria in beer, being an indicator of contamination for these bacteria. In conclusion, we observed that 8 out of 10 breweries studied showed contamination problems, highlighting the need to design prevention and control strategies in microbreweries.

The diversity, extracellular enzymatic activities and photoprotective compounds of yeasts isolated in Antarctica

The diversity of yeasts collected from different sites in Antarctica (Admiralty Bay, King George Island and Port Foster Bay and Deception Island) and their ability to produce extracellular enzymes and mycosporines were studied. Samples were collected during the austral summer season, between November 2006 and January 2007, from the rhizosphere of Deschampsia antarctica, ornithogenic (penguin guano) soil, soil, marine and lake sediments, marine water and freshwater from lakes. A total of 89 isolates belonging to the following genera were recovered: Bensingtonia, Candida, Cryptococcus, Debaryomyces, Dioszegia, Exophiala, Filobasidium, Issatchenkia (Pichia), Kodamaea, Leucosporidium, Leucosporidiella, Metschnikowia, Nadsonia, Pichia, Rhodotorula, and Sporidiobolus, and the yeast-like fungi Aureobasidium, Leuconeurospora and Microglossum. Cryptococcus victoriae was the most frequently identified species. Several species isolated in our study have been previously reported to be Antarctic psychophilic yeasts, including Cr. antarcticus, Cr. victoriae, Dioszegia hungarica and Leucosporidium scottii. The cosmopolitan yeast species A. pullulans, C. zeylanoides, D. hansenii, I. orientalis, K. ohmeri, P. guilliermondii, Rh. mucilaginosa, and S. salmonicolor were also isolated. Five possible new species were identified. Sixty percent of the yeasts had at least one detectable extracellular enzymatic activity. Cryptococcus antarcticus, D. aurantiaca, D. crocea, D. hungarica, Dioszegia sp., E. xenobiotica, Rh. glaciales, Rh. laryngis, Microglossum sp. 1 and Microglossum sp. 2 produced mycosporines. Of the yeast isolates, 41.7 percent produced pigments and/or mycosporines and could be considered adapted to survive in Antarctica. Most of the yeasts had extracellular enzymatic activities at 4ºC and 20ºC, indicating that they could be metabolically active in the sampled substrates.