RESUMEN
Penicillium nordicum is one of the major producers of ochratoxin A (OTA) in dry-cured ham. Staphylococcus xylosus Sx8 and Staphylococcus equorum Se31 have been previously proposed as biocontrol agents (BCAs) to prevent the OTA contamination, although their antifungal mode of action has not been established yet. Thus, the aim of this work was to elucidate their mode of action against P. nordicum in a dry-cured ham model system. For this, the effect of live cells, dead cells, and cell-free broth; the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays, antifungal effect of volatile compounds, OTA detoxification, and effect on fungal proteome were determined. No fungal growth was observed after 14 days of co-culture with live cells of each staphylococcus at 15 or 20 °C. However, such inhibition was not observed with either dead cells or extracellular extracts. The number of carbon sources utilised by P. nordicum was higher than those used by both cocci at 20 °C, whilst the opposite occurred at 15 °C. According to NOI, nutritional dominance depends on temperature, at 20 °C P. nordicum dominated the niche, but at 15 °C the mould is dominated by the BCAs. The volatile pattern generated by each coccus did not show antifungal effect, and both staphylococci failed to degrade or adsorb OTA. However, in the interaction assay, S. xylosus and S. equorum were able to decrease the fungal growth and its OTA production. In addition, proteomic analyses showed changes in the abundance of proteins related to the cell wall integrity (CWI), carbohydrate metabolism and the biosynthesis of secondary metabolites such as OTA. In conclusion, overall, the antagonistic effects of the two studied cocci against P. nordicum are greater at 15 °C than at 20 °C, being linked to competition for space and nutrients, triggering alterations in CWI pathway, OTA biosynthesis, and carbohydrate metabolism.
Asunto(s)
Productos de la Carne , Ocratoxinas , Penicillium , Carne de Cerdo , Microbiología de Alimentos , Carne de Cerdo/análisis , Proteómica , Antifúngicos/metabolismo , Productos de la Carne/microbiología , Penicillium/metabolismo , Staphylococcus/metabolismoRESUMEN
Amending municipal solid waste incineration (MSWI) with carbon capture and utilisation (CCU) can simultaneously lower the climate change impacts of incineration and supply carbon for a range of uses. However, life cycle assessment (LCA) shows that technology choices and the benefits of CCU applied to MSWI depend on the energy system in which the MSWI operates throughout its lifetime, and on the markets for the CCU products. Carbon capture reduces up to 50% of the energy recovery of MSWI. We assessed different energy system scenarios, ranging from fossil- to non-fossil based. Direct utilisation of the captured CO2 is beneficial only on a local basis when substituting fossil-based CO2 (-700 kg CO2-eq/tonne waste), with benefits similar to carbon capture and storage. Hydrogenation of CO2 with the purpose of producing feedstock chemicals or fuels such as methane, methanol, dimethyl ether (DME) and formic acid provides much higher benefits (-2000 kg CO2-eq/tonne waste), but only in non-fossil-based energy systems, due to the dramatically high consumption of electricity (more than 6000 kWh/tonne waste). Use as feedstock chemicals provides more benefits than use as fuels, and CCU solutions focusing on methanol and DME are the most promising technologies. Although built on scarce and early-development data, the analysis highlights current crucial issues, at both the technological and system levels, for the future introduction of CCU in MSWI.
Asunto(s)
Cambio Climático , Incineración , Carbono , Metano , Residuos Sólidos/análisisRESUMEN
The environmental conditions during the ripening of dry-cured meats and their nutritional composition promote the colonisation of their surface by Penicillium spp., including P. nordicum producer of ochratoxin A (OTA). The objective of this work was to study the competitiveness of three potential biocontrol candidates (Debaryomyces hansenii FHSCC 253H, Enterococcus faecium SE920 and Penicillium chrysogenum CECT, 20922) against the ochratoxigenic P. nordicum FHSCC4 under environmental and nutritional conditions simulating the ripening of dry-cured meat products. For this, the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays and OTA production were determined. The number of carbon sources (CSs) metabolised depended on the microorganism and the interacting water activity (aw) x temperature conditions. The number of CSs utilised by both filamentous fungi was quite similar and higher than those utilised by D. hansenii and E. faecium. The yeast isolate metabolised a number of CSs much larger than the bacterium. The NOI values showed that, in general, P. nordicum nutritionally dominated E. faecium and D. hansenii regardless of the environmental conditions evaluated. The relationship between the toxigenic and non-toxigenic fungal isolates depended on the aw x temperature combinations, although in none of the conditions a dominance of P. nordicum was observed. According to the interaction assays, both D. hansenii and P. chrysogenum decreased the growth of P. nordicum. The effect of D. hansenii could be attributed to the production of some extra-cellular compounds, while the action of P. chrysogenum is likely related to nutritional competition. In addition, both P. chrysogenum and D. hansenii reduced the OTA levels produced by P. nordicum. The effect of the yeast was more pronounced decreasing the concentration of OTA at quantities lower than the limit established by the Italian legislation. Therefore, P. chrysogenum and D. hansenii can be suggested as biocontrol candidates in the manufacture of dry-cured meat products.
Asunto(s)
Agentes de Control Biológico , Microbiología de Alimentos , Productos de la Carne , Interacciones Microbianas , Penicillium , Enterococcus faecium/fisiología , Microbiología de Alimentos/métodos , Alimentos en Conserva/microbiología , Productos de la Carne/análisis , Productos de la Carne/microbiología , Interacciones Microbianas/fisiología , Ocratoxinas/análisis , Ocratoxinas/metabolismo , Penicillium/fisiología , Penicillium chrysogenum/fisiología , Saccharomycetales/fisiologíaRESUMEN
Bacterial diversity underpins many ecosystem functions; however, the impact of within-species variation on the relationship between diversity and function remains unclear. Processes involving strain differentiation, such as niche radiation, are often overlooked in studies that focus on phylogenetic variation. This study used bacterial isolates assembled in two comparable microcosm experiments to test how species variation affected ecosystem function. We compared the relationship between diversity and activity (CO2 production) in increasingly diverse multispecies microcosms and with multiple ecotypes of a single species. The bacteria used were isolated from a low-diversity environment and are species of potential clinical significance such as Pseudomonas aeruginosa. All isolates were profiled for single carbon source utilisation. These data showed an increased breadth of resource use in the multiple ecotypes when compared to the mixed-species. The study observed significantly increasing respiration in more complex mixed-species assemblages, which was not observed when ecotypes of a single species were combined. We further demonstrate that the variation observed in the bacterial activity was due to the roles of each of the constituent isolates; between different species, the interactions between the isolates drove the variation in activity, whilst in single species, assemblage variation was due to which isolates were present. We conclude that both between- and within-species variations play different roles in community function, although through different mechanisms, and should be included in models of changing diversity and ecosystem functioning.
Asunto(s)
Fenómenos Fisiológicos Bacterianos , Dióxido de Carbono/metabolismo , Microbiota , Pseudomonas aeruginosa/fisiología , Bacterias/clasificación , Ecotipo , Filogenia , Pseudomonas aeruginosa/genéticaRESUMEN
Brettanomyces bruxellensis is a common red wine spoilage yeast. Yet, in addition to wine, it has been isolated from other ecological niches that are just as nutritionally deficient as wine. B. bruxellensis can therefore be regarded as a survivor, well adapted to colonise harsh environments not often inhabited by other yeasts. This review is focused on the nutritional requirements of B. bruxellensis and the relevance thereof for its adaptation to the different matrices within which it occurs. Furthermore, the environmental conditions necessary (e.g. aerobic or anaerobic conditions) for the assimilation of the carbon or nitrogenous sources are discussed in this review. From literature, several confusing inconsistencies, regarding nutritional sources necessary for B. bruxellensis survival, in these specialist ecological niches are evidenced. The main focus of this review is wine but other products and niches that B. bruxellensis inhabits namely beer, cider, fruit juices and bioethanol production plants are also considered. This review highlights the lack of knowledge regarding B. bruxellensis when considering its nutritional requirements in comparison to Saccharomyces cerevisiae. However, there is a large enough body of evidence showing that the nutritional needs of B. bruxellensis are meagre, explaining its ability to colonise harsh environments.