Browsing by Author "Medina-Vaya, Angel"

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    Biocontrol of ochratoxigenic fungi by endogenous lactic acid bacteria and yeasts from ivorian robusta coffee in the context of climate change
    (Cranfield University, 2023-09) Lopez Rodriguez, Claudia; Medina-Vaya, Angel; Schorr-Galindo, Sabine; Verheecke-Vaessen, Carol; Fontana, Angelique; Strub, Caroline
    This doctoral research delves into the innovative domain of biocontrol strategies targeting mycotoxigenic fungi in the context of climate change. Focusing on Ivorian coffee, a vital economic and agricultural commodity, the study explores the potential of indigenous lactic acid bacteria (LAB) and yeasts as biocontrol agents. Mycotoxins, toxic secondary metabolites produced by fungi, pose significant health risks and economic losses. As climate change amplifies the proliferation of mycotoxigenic fungi, the demand for sustainable and eco-friendly interventions intensifies. The research encompasses comprehensive isolation, identification, and characterization of LAB and yeasts from Ivorian coffee, evaluating their antagonistic properties against mycotoxigenic fungi. Furthermore, the study elucidates the mechanisms underlying the biocontrol activity, shedding light on how these microorganisms mitigate mycotoxin contamination. This research is pivotal in the pursuit of climate-resilient strategies for mycotoxin management, contributing to both food safety and agricultural sustainability.
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    Impact of carbon sources in airport de-icing compounds on the growth of Sphaerotilus natans
    (Frontiers Media SA, 2024-10-23) Exton, Benjamin; Hassard, Francis; Medina-Vaya, Angel; Grabowski, Robert C.
    Airport de-icing has been linked with the growth of undesirable river biofilms (URBs, formerly “sewage fungus”), a manifestation of organic pollution causing long-term ecological damage to watercourses. URBs are a polymicrobial community, with one key taxon standing out in literature: Sphaerotilus natans, a filamentous bacterium also found in sewage treatment and activated sludges. An industry often implicated in causing URBs is airport de-icing, with large biofilms often developing downstream of airport discharges in winter months. However, it is not yet clear which de-icers may cause URBs and how they influence growth. Therefore, specific objectives were to (i) determine which freeze-point depressants (FPDs) can be utilized by S. natans; (ii) examine differences in the growth kinetics between FPDs; and (iii) compare pure-FPDs to commercial airport de-icers (CADs) as carbon sources, to determine impacts of additives. This study employed a turbidimetric micro-batch culture design to conduct microbial growth experiments, using S. natans and a minimal medium supplemented with airport de-icer as the carbon source. Equimolar carbon concentrations were used to compare the effects of common FPDs and CADs – each containing a specific FPD. Growth was assessed via optical density (OD600) measurements, from which time-to-detection, maximum rate of change, and maximum optical density were derived and kinetics inferred. S. natans was found to grow effectively on all FPDs tested, although the microbial yield was heavily dependent on the carbon concentration for all FPDs and CADs. Sodium acetate generated the quickest growth, with the lowest TTD (lag-time) for all but the lowest concentrations tested. Propylene glycol produced the greatest maxOD (total growth), whereas ethylene glycol had a higher limiting concentration for maxROC (growth rate). The mixture of compounds and additives in commercial products did not significantly impact the growth of S. natans. This research provides evidence from controlled laboratory experiments that airport de-icers support the growth of S. natans. The differences in growth kinetics observed for the FPDs and CADs could inform improved mitigation or treatment to reduce the incidence and ecological impacts of URBs.
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    The epidemiology and management of cladosporium on raspberry
    (Cranfield University, 2024-01) Farwell, Lauren; Xu, Xiangming; Medina-Vaya, Angel
    Cladosporium is a genus of fungi that causes dark mycelial lesions on raspberries, rendering fruit unmarketable. As Cladosporium is an opportunistic pathogen, its prevalence varies across years, and there is insufficient research on its epidemiology and management. This study aimed to investigate the epidemiology of Cladosporium on raspberries and to elucidate which management strategies could be effective. Isolates of Cladosporium were obtained from raspberries, with C. cladosporioides being the most predominant, and was therefore used in further experiments. The susceptibility of raspberry fruit development was determined, with ripening and ripe fruit found to be susceptible to skin lesions; this stage of development was subsequently targeted in management studies. The effects of ripening and fruit location (fruit location within a tunnel vs. across a farm) on the inoculum load on the surface of raspberries were investigated using metabarcoding studies. The fungal and bacterial microbiomes were also investigated to better elucidate the ecology of Cladosporium on the fruit surface. Cladosporium was more abundant on green fruit than ripening fruit; perhaps due to organisms such as Rouxiella present on the fruit’s surface. Fungal α diversity increased during ripening while bacterial diversity decreased. The Cladosporium inoculum load in the air was also investigated, with more spores trapped inside a raspberry polytunnel than an open field. The efficacy of commercial Biological Control Agents (BCAs) and resistant varieties to control Cladosporium skin lesions were tested across two years in field applications. The Trichoderma sp. was the most effective at reducing the incidence of Cladosporium on raspberry than compared to the other tested products. The variety resistance study was inconclusive, but results indicate further testing will reveal which varieties are more susceptible. This research will inform potential management strategies against Cladosporium on raspberries that will aid growers in reducing food waste sustainably