Early detection of Aspergillus carbonarius and A. niger on table grapes: a tool for quality improvement

Aspergillus carbonarius and A. niger aggregate are the main fungal contaminants of table grapes. Besides their ability to cause black rot, they can produce ochratoxin A (OTA), a mycotoxin that has attracted increasing attention worldwide. The objective of this work was to set up a simple and rapid molecular method for the early detection of both fungi in table grapes before fungal development becomes evident. Polymerase chain reaction (PCR)-based assays were developed by designing species-specific primers based on the polyketide synthases (PKSS) sequences of A. carbonarius and A. niger that have recently been demonstrated to be involved in OTA biosynthesis. Three table grape varieties (Red globe, Crimson seedless, and Italia) were inoculated with A. carbonarius and A. niger aggregate strains producing OTA. The extracted DNA from control (non-inoculated) and inoculated grapes was amplified by PCR using ACPKS2F-ACPKS2R for A. carbonarius and ANPKS5-ANPKS6 for A. niger aggregate. Both primers allowed a clear detection, even in symptomless samples. PCR-based methods are considered to be a good alternative to traditional diagnostic means for the early detection of fungi in complex matrix for their high specificity and sensitivity. The results obtained could be useful for the definition of a 'quality label' for tested grapes to improve the safety measures taken to guarantee the production of fresh table grapes

Two rapid assays for screening of patulin biodegradation

Artículo sobre distintos ensayos para comprobar la biodegradación de la patulinaThe mycotoxin patulin is produced by the blue mould pathogen Penicillium expansum in rotting apples during postharvest storage. Patulin is toxic to a wide range of organisms, including humans, animals, fungi and bacteria. Wash water from apple packing and processing houses often harbours patulin and fungal spores, which can contaminate the environment. Ubiquitous epiphytic yeasts, such as Rhodosporidium kratochvilovae strain LS11 which is a biocontrol agent of P. expansum in apples, have the capacity to resist the toxicity of patulin and to biodegrade it. Two non-toxic products are formed. One is desoxypatulinic acid. The aim of the work was to develop rapid, high-throughput bioassays for monitoring patulin degradation in multiple samples. Escherichia coli was highly sensitive to patulin, but insensitive to desoxypatulinic acid. This was utilized to develop a detection test for patulin, replacing time-consuming thin layer chromatography or high-performance liquid chromatography. Two assays for patulin degradation were developed, one in liquid medium and the other in semi-solid medium. Both assays allow the contemporary screening of a large number of samples. The liquid medium assay utilizes 96-well microtiter plates and was optimized for using a minimum of patulin. The semisolid medium assay has the added advantage of slowing down the biodegradation, which allows the study and isolation of transient degradation products. The two assays are complementary and have several areas of utilization, from screening a bank of microorganisms for biodegradation ability to the study of biodegradation pathways

Biosintesi e controllo delle micotossine negli alimenti

Mycotoxins are harmful secondary metabolites produced by several widespread environment-contaminating fungi mainly belonging to Fusarium, Aspergillus and Penicillium genera. These compounds can be mutagenic, teratogenic and carcinogenic for animals and humans. In our diet we experience a quite harmful daily consumption of mycotoxin-contaminated foods. But why fungi do produce toxins? And how are their biosynthesis regulated? Some mycotoxins have a clear-cut role in the assessment of pathogenesis, i.e. fumonisins and some trichothecene, in the competition with other organisms, i.e. patulin vs bacteria. In other cases, such as aflatoxins, more than one role can be hypothesised. Several are the inputs able to modulate mycotoxin synthesis. Here we have focused our attention on those whose regulatory mechanisms have been assessed. In particular, some of these pathways seem to have a common factor which is represented by the control exerted by the reactive oxygen species. In fact, when a fungus receives an external stimulus reacts by activating, through a quite well-defined signal cascade, an evident switch in its lifestyle. This profound change also lead to the activation of global gene regulators and, in particular, of transcription factors able to enhance the mycotoxin gene cluster expression. The control exerted by oxidative stress onto the mycotoxin synthesis has lead to use antioxidants of different origin for blocking the synthesis of these harmful compounds both in the field and in the storage. Recently, many natural-based antioxidant or biocontrol-related strategies have been assessed as environment-friendly approaches for controlling the production of many mycotoxins in feed and foodstuffs

Effect of different antifungals on the control of paper biodeterioration caused by fungi

The inhibition of some fungal strains responsible for paper biodeterioration is reported. Antimicrobials (butylated hydroxytoluene, BHT and butylated hydroxyanisole, BHA), azole antifungals (econazole, miconazole and ketoconazole) and chitin synthase inhibitors (uridine, 5-fluorouridine, 2-deoxyuridine) have been assessed for efficacy against Penicillium chrysogenum Thom, Aspergillus terreus Thom, Stachybotrys atra Corda and Chaetomium elatum Kunze, fungal strains isolated from deteriorated papers. Our results have shown that the most evident inhibiting effect on fungal growth has been obtained with miconazole and econazole at 10−3 M

3rd International Symposium on Postharvest Pathology: Using Science to Increase Food Availability

Controlling microbial contamination is a critical aspect of reducing losses of harvested apple fruit during storage. The use of synthetic pesticides is still an essential tool; however, the future use of these compounds is increasingly limited due to the onset of pathogen resistance and to growing consumer demand for fruits free of pesticide residues. In this work, we evaluated two different strategies for the storage 'of 'Cripps Pink' apples. In the first one, the apples were sprayed with electrolyzed water (EW) at 400 mg L-1of free available chlorine (FAC) in the field before harvest, and were then stored at 1°C under controlled atmosphere for 4 months. At the end of the storage period, the percentage of rotted apples, especially with regard to Gloesporium spp. rotting, was evaluated and compared to the percentage of conventionally treated (pyraclostrobin+boscalid) apples. In the second storage strategy, apples were not treated with EW in the field, but moved directly to the storage facility after harvest, where they were stored for 2 months at 1°C in controlled atmosphere, and then either washed with working line water, or washed by dipping in EW at 50 mg L-1or washed by spraying with EW at 400 mg L-1FAC. After washing, the apples were stored at 25°C and checked every seven days. The bacterial contamination of washing water and the presence of pesticide residues on apples were also analyzed. The results evidenced that the percentage of rotted apples was significantly lower if the apples were treated with EW at 400 mg L-1of FAC before harvest. EW can be considered as an effective means of controlling microbial contamination and rotting. EW also can reduce the pesticide residues in 'Cripps Pink' apples