Mycotoxins Microbial toxins Classified into three major group
Mycotoxins
Microbial toxins Ø Classified into three major group: 1. Bacterial toxins: produced by bacteria. 2. Phycotoxins: produced by algae. 3. Mycotoxins: produced by fungi.
Mycotoxins • A mycotoxin (from Greek (mykes, mukos) "fungus" and (toxikon) "poison") is a toxic secondary metabolite produced by fungi. • One mold species may produce many different mycotoxins, and the same mycotoxin may be produced by several species.
What is a Mycotoxin? • A mycotoxin (from Greek (mykes, mukos) "fungus" and (toxikon) "poison") is a toxic secondary metabolite produced by fungi. • One mold species may produce many different mycotoxins, and the same mycotoxin may be produced by several species. • Lack of visible appearance of fungus does not negate presence of mycotoxins. Toxins can remain in the organism after fungus has been removed. • Less selective in organism selection. • Can be heat stable, not destroyed by heating.
• In considering the effects of mycotoxins, it is important to distinguish between “mycotoxicosis” and “mycosis”: • Mycotoxicosis is used to describe the action of mycotoxin(s) and is frequently mediated through a number of organs, notably the liver, kidney, lungs, and the nervous, endocrine, and immune systems. • Mycosis refers to a generalized invasion of living tissue(s) by growing fungi. 5
Information About Fungus • Range from single cells to fruiting bodies that form molds, mushrooms, smuts, and yeasts. • Absorb nutrients from living or deceased organisms, contain no chlorophyll. • If multicellular, they have tubular filaments called hyphae that branch out. • Reproduce using spores.
Modes of Spore Transmission • Airborne, wind or indoor ventilation systems. • Attachment to insects or birds, thus transmitted from plant to plant, or animal to animal, etc. • Via transportation mechanisms such as trucks, crop machinery, etc.
Fungal Infection • • • Can occur at any stage in crop production. While in the field. During harvesting. While in storage. Spores can lay dormant for months to years, waiting for positive conditions for germination.
Conditions to Encourage Fungal Growth • Relative humidity over 70%. • Temperatures over 30 degrees Celsius for a period of a few days to a week. • Stress to the affected plant, such as drought, flood, or insect infestation. • High moisture content of crop (20% or higher).
Locales of Mycotoxins • In North America, grain producing areas spread from central Canada to the southern parts of the US. • These grains are then exported to Asia, the Pacific Islands, South and Central America, Europe, the Middle East, India and Africa.
Mycotoxin Statistics • 300 -400 mycotoxins presently identified, with more becoming evident as new isolation techniques are used. • Most frequent toxins present are aflatoxin, deoxynivalenol (DON), zearalenone (ZEN), fumonisin, and T-2 toxin, to name a few.
Mycotoxin Health Hazards • Generally lower risk in well developed countries due to improved standards of living. • High intake of affected product, usually in conjunction with limited amounts of other food sources. • Greatest threat comes from long term exposure due to eating spoiled food or meat from animals fed contaminated feed.
Symptoms of Mycotoxicosis 1. Drugs and antibiotics are not effective in treatment. 2. The symptoms can be due to foodstuffs or feed. 3. Testing of foodstuffs or feed reveals fungal contamination. 4. The symptoms are not transmissable person to person. 5. The degree of toxicity is subject to persons age (more often in very young and very old), sex ( more often in females than males)and nutritional status. 6. Outbreaks of symptoms appear seasonally.
Mycotoxin Effects on Humans • Economic loss due to impaired health of stock animals. • Illness: symptoms can include cold/flu-like symptoms, sore throats ﺍﻟﺘﻬﺎﺏ ﺍﻟﺤﻠﻖ , headaches, nose bleeds ﻧﺰﻳﻒ ﺍﻷﻨﻒ , fatigue ﺍﺭﻫﺎﻕ , diarrhea ﺍﻹﺳﻬﺎﻝ , dermatitis ﺍﻟﺘﻬﺎﺏ ﺍﻟﺠﻠﺪ , and immune suppression ﺿﻌﻒ ﺍﻟﻤﻨﺎﻋﺔ , and vary by species. • Death.
Mycotoxin Effects on Animals • Feed refusal. • Impaired animal health, resulting in reduced production of eggs, milk, weight gain, etc. • Metabolites are passed through the milk in cheese, dry milk, and yogurt. • Disease. • Death in animals.
PRODUCTION OF MYCOTOXINS BY TOXICOGENIC FUNGI Invasion by fungi and production of mycotoxins can occur under favorable conditions in the field, at harvest, and during transportation and storage. Ø Fungi that are frequently found in the field include: A. flavus, Alternaria longipes, A. alternata, Claviceps purpura, Fusarium verticillioides, F. graminearum, and a number of other Fusarium spp. Ø Species most likely introduced at harvest include: F. sporotrichioides, Stachybotrys atra, Cladosporium sp. , Myrothecium verrucaria, Trichothecium roseum, as well as A. alternata. All of which are capable of producing mycotoxins in grains and foods.
Ø Most penicillia are storage fungi. These include: • Penicillium citrinum, P. cyclopium, P. citreoviride, P. islandicum, P. rubrum, P. viridicatum, P. urticae, P. verruculosum, P. palitans, P. puberulum, P. expansum, and P. roqueforti. Ø Other toxicogenic storage fungi are: • Aspergillus parasiticus, A. flavus, A. versicolor, A. ochraceus, A. clavatus, A. fumigatus, A. rubrum, A. chevallieri, Fusarium verticillioides, F. tricinctum, F. nivale, and several other Fusarium spp. Ø It is apparent, most of the mycotoxin producing fungi belong to three genera: Aspergillus, Fusarium, and Penicillium. However, not all species in these genera are toxicogenic
Aflatoxin • are naturally occurring mycotoxins that are produced by Aspergillus flavus and Aspergillus parasiticus. • Aflatoxins are toxic and among the most carcinogenic substances known. • After entering the body, aflatoxins may be metabolized by the liver to the less harmful aflatoxin M 1.
• Sources : Aflatoxin Aspergillus flavus & A. parasiticus : Corn, sorghum, peanuts and cotton • Factor favoring production of aflatoxins: a. Temperature : 25 -30 ⁰c. b. Grain moisture. c. high-humidity environment. d. damage from stressful conditions such as drought, heat, insect, nematode and fertilizer stress.
Physical and Chemical properties • Stable at temperature > 100 ⁰C and under UV radiation. • Exhibit intense blue or green fluorescence under UV.
Chemical structure of aflatoxin B 1
Types of aflatoxins Ø Aflatoxin B 1 & B 2, produced by Aspergillus flavus and A. parasiticus. Ø Aflatoxin G 1 & G 2, produced by Aspergillus parasiticus. Ø Aflatoxin M 1, metabolite of aflatoxin B 1 in humans and animals. Ø Aflatoxin M 2, metabolite of aflatoxin B 2 in milk of cattle fed on contaminated foods.
v Aflatoxin B 1 is considered the most toxic. v While the presence of Aspergillus in food products does not always indicate harmful levels of aflatoxin are also present, it does imply a significant risk in consumption. v Aflatoxins M 1, M 2 were originally discovered in the milk of cows that fed on moldy grain. These compounds are products of a conversion process in the animal's liver.
Contaminated food products • sources of commercial maize, sorghum, wheat, peanut butter, oils (e. g. olive, peanut, soybean, cotton and sesame oil), spices, milk and cosmetics have been identified as contaminated with aflatoxin
Symptoms • • • Liver necrosis. Liver tumors. Reduced growth. Depressed immune response. Carcinogen.
• High-level aflatoxin exposure produces an acute hepatic necrosis, resulting later in cirrhosis, or carcinoma of the liver. • Acute liver failure is made manifest by bleeding, edema, alteration in digestion, changes to the absorption and/or metabolism of nutrients, and mental changes and/or coma.
• Medical research indicates that a regular diet including vegetables, such as carrots, parsnips, celery and parsley, may reduce the carcinogenic effects of aflatoxin.
Methods to decrease aflatoxins • Roasting of food may cause 40 -60% reduction. • Alkaline treatment of food destroy aflatoxins. • Fermentation of contaminated seeds with aflatoxins cause of a loss of 60% of added aflatoxins.
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