Potential of two Metschnikowia pulcherrima (yeast) strains for in vitro biodegradation of patulin.

Patulin contamination of apple and other fruit-based foods and beverages is an important food safety issue, as consumption of these commodities throughout the world is great. Studies are therefore necessary to reduce patulin levels to acceptable limits or undetectable levels to minimize toxicity. This study was undertaken to investigate the efficacy of two Metschnikowia pulcherrima strains (MACH1 and GS9) on biodegradation of patulin under in vitro conditions. These yeast strains were tested for their abilities to degrade patulin in liquid medium amended with 5, 7.5, 10, and 15 µg/ml patulin and a yeast cell concentration of 1 × 10(8) cells per ml at 25°C. Of the two strains tested, MACH1 completely (100%) reduced patulin levels within 48 h, and GS9 within 72 h, at all concentrations of patulin. MACH1 effectively degraded the patulin within 24 h by 83 to 87.4%, and GS9 by 73 to 75.6% at 48 h, regardless of concentration. Patulin was not detected in yeast cell walls. This indicates that yeast cell walls did not absorb patulin, and that they completely degraded the toxin. Patulin had no influence on yeast cell concentration during growth. Therefore, these yeast strains could potentially be used for the reduction of patulin in naturally contaminated fruit juices. To our knowledge, this is the first report regarding the potential of M. pulcherrima strains for patulin biodegradation.

Molecular characterization of pathogenic Fusarium species in cucurbit plants from Kermanshah province, Iran.

Fusarium is one of the important phytopathogenic genera of microfungi causing serious losses on cucurbit plants in Kermanshah province, the largest area of cucurbits plantation in Iran. Therefore, the objectives in this study were to isolate and identify disease-causing Fusarium spp. from infected cucurbit plants, to ascertain their pathogenicity, and to determine their phylogenetic relationships. A total of 100 Fusarium isolates were obtained from diseased cucurbit plants collected from fields in different geographic regions in Kermanshah province, Iran. According to morphological characters, all isolates were identified as Fusarium oxysporum, Fusarium proliferatum, Fusarium equiseti, Fusarium semitectum and Fusarium solani. All isolates of the five Fusarium spp. were evaluated for their pathogenicity on healthy cucumber (Cucumis sativus) and honeydew melon (Cucumis melo) seedlings in the glasshouse. F. oxysporum caused damping-off in 20-35 days on both cucurbit seedlings tested. Typical stem rot symptoms were observed within 15 days after inoculation with F. solani on both seedlings. Based on the internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) restriction fragment length polymorphism (RFLP) analysis, the five Fusarium species were divided into two major groups. In particular, isolates belonging to the F. solani species complex (FSSC) were separated into two RFLP types. Grouping among Fusarium strains derived from restriction analysis was in agreement with criteria used in morphological classification. Therefore, the PCR-ITS-RFLP method provides a simple and rapid procedure for the differentiation of Fusarium strains at species level. This is the first report on identification and pathogenicity of major plant pathogenic Fusarium spp. causing root and stem rot on cucurbits in Iran.

A preliminary study on the occurrence of Aspergillus spp. and aflatoxin B1 in imported wheat and barley in Penang, Malaysia.

Thirty samples consisting of wheat (15) and barley (15) were collected from different markets in Penang, Malaysia, originating from India and Thailand, respectively. All samples were analyzed for occurrence of Aspergillus spp. and aflatoxin B1 (AFB1). Aspergillus flavus was dominant in all samples followed by A. niger. AFB1 could be detected in three wheat samples ranging from 0.42 to 1.89 µg/kg and one barley sample had 0.58 µg/kg of AFB1. The AFB1 levels in all the samples were below the Malaysian regulatory limits (<35 µg/kg). The frequency and quantity of AFB1 levels in this study were very low in wheat and barley samples compared to other agricultural commodities reported in India and Thailand. This is the first report on determination of Aspergillus spp. and AFB1 in imported wheat and barley grains in Penang, Malaysia.

Potential of patulin production by Penicillium expansum strains on various fruits.

In this study, we investigated the pathogenicity and patulin production by ten strains of Penicillium expansum on various fruits (apples, apricots, kiwis, plums and peaches) at two (4°C and 25°C) different temperature regimes. All strains caused the infectious rots on all fruits at 4 and 25°C except one strain (PEX 09) at 4°C. Two strains (PEX 20 and PEX 12) out of ten produced the highest amounts of patulin on all fruits tested. The patulin production by P. expansum is high at 25°C compared to 4°C. All strains of P. expansum accumulated patulin ranging from 100-13,200 µg/kg and nine strains ranging from 100-12,100 µg/kg in all fruits at 25°C and 4°C, respectively. Among ten strains of P. expansum, strain PEX 20 produced the greatest amount of patulin on apricots (13,200 µg/kg of rotten fruit) and on apples (12,500 µg/kg) at 25°C after 9 days of incubation. At 4°C, this strain produced 12,100, 12,000, 2,100 and 1,200 µg/kg of patulin on apricots, apples, plums and peaches, respectively, after 45 days of incubation. Strain PEX 12 produced the highest amount of patulin on kiwis (10,700 µg/kg) at 25°C and 10,300 µg/kg at 4°C. Patulin production by P. expansum on peaches and plums at both temperatures were lower than other fruits. The results of this study showed that careful removal of rotten fruits is essential to produce patulin-free fruit juice, since high patulin levels in apricots, apples and kiwis could result in a level greater than 50 µg/kg of this mycotoxin in finished fruit juices, when one contaminated fruit occurs in 264, 250 and 214 fruits, respectively. So, the fruit processors should take care in not using rotten fruits for juice production to avoid the patulin problem worldwide, since this study proved that most important fruits being used for juice production and direct human consumption are susceptible to P. expansum and subsequent patulin production even at low temperatures. This is the first comprehensive report regarding patulin production by different strains of P. expansum on various fruits from Italy at different temperature regimes.

Morphological identification of foodborne pathogens colonizing rice grains in south Asia.

The aim of this study was to identify the foodborne pathogens mainly, Aspergillus sp. colonizing rice grains using cultural and microscopic methods. Four differential media (Czapek Dox Agar (CZA), Czapek Yeast Agar (CYA), Malt Extract Agar (MEA) and Czapek yeast 20% sucrose agar (CYA20S)) were used for differentiation of five Aspergillus sp., colonizing rice grains comparing with standard cultures. We studied macroscopic (colony color and diameter, conidia color, exudates, sclerotia and colony texture) and microscopic (conidiophore color, length and breadth, conidia size, shape and surface texture, vesicle diameter and phialides length and breadth) characteristics for identification of 110 isolates of Aspergillus sp. isolated from 65 rice grain samples collected from various countries in South Asia (Cambodia, India, Indonesia, Malaysia and Thailand). According to morphological characters, all these isolates were belonging to Aspergillus flavus (45), A. fumigatus (8), A. ochraceus (7), A. niger (42) and A. tamarii (8). This is the first report on identification of large number of Aspergillus strains isolated from rice grains in South Asia.

Detection of Aspergillus spp. and aflatoxin B1 in rice in India.

Twelve hundred rice samples consisting of paddy (675) and milled rice (525) were collected from 20 states across India. These samples were assessed for Aspergillus spp. infection on selective medium and aflatoxin B(1) (AFB1) by indirect competitive ELISA. In this investigation, Aspergillus flavus contamination dominated in all the seed samples. The other major contaminants were Aspergillus niger, Aspergillus ochraceus and Aspergillus parasiticus. Out of 1200 rice samples, 67.8% showed AFB1 ranging from 0.1 to 308.0 microg/kg. All the paddy samples from Chattishgarh, Meghalaya and Tamil Nadu showed AFB1 contamination. Milled rice grains from different states showed below the permissible levels of AFB1 (average 0.5-3.5 microg/kg). Eighty-two percent of samples from open storage that were exposed to rain showed AFB1 contamination followed by one-year-old seed. Out of 1200 samples, 2% showed AFB1 contamination above the permissible limits (>30 microg/kg). This is the first comprehensive report of aflatoxin contamination in rice across 20 states in India.