Why do fungi produce mycotoxins

Contamination of Swedish cereals with ochratoxin A. Leigh, C. The chemistry of epipolythiopiperazine-3,6-diones. Lillehoj, E. Mycotoxin synergism. In: Microbiology Aspergillus flavus and aflatoxin in Iowa corn before harvest. Marsh, P. Simpson, G. Craig, J. Ramey, Jr. Ocurrence of aflatoxins in cottonseeds at harvest in relation to location of growth and field temperatures. Pathre, S. Zearalenone and related compounds. Russell, T. Field Field accumulation of aflatoxin in cottonseed as influenced by irrigation termination dates and pink bollworm infestation.

Scott, P. Miles, P. Occurrence of patulin in apple juice. Food Chem. Mycotoxins ochratoxin A, citrinin and sterigmatocystin and toxigenic fungi in grains and other agricultural products. Shotwell, O. Hesseltine, E. Survey of corn from different regions for aflatoxins, ochratoxin and zearalenone. Cereal Sci.

Today — Stoloff, L. Occurrence of mycotoxins in foods and feeds. Rodricks ed. Uchiyama, M. A case report on the detection of ochratoxin A from rice. Food Hyg. Ukai, T. Substance from a strain of Penicillium. Culture method of Hori-Yamamoto strain and chemical structure of its poisonous substance.

Vesonder, R. Cultures such as coffee, rice, and spices can also be contaminated by these toxins post-crop [ 26 ]. Many countries introduced legislation specific to mycotoxins. Most of these legislation rules are regarding aflatoxins, alkaloids of ergot, deoxynivalenol, and ochratoxins. Even though legal measures are yet to be uniformed at a worldwide level, the Codex Alimentarius Commission is gathering efforts to establish international guidelines regarding levels of mycotoxins.

For aflatoxins, the Food and Drug Administration established the maximum limit of 20 ppb to maize, peanut, cotton bran, and other food and ingredients for animals [ 27 , 28 , 29 , 30 , 31 ].

The major toxins produced by Penicillium verrucosum , Aspergillus ochraceus , and Aspergillus carbonarius are ochratoxin A, ochratoxin B, and ochratoxin C. Among these toxins, ochratoxin A is considered the most toxic and, according to the IARC, a possible cancer-causing substance to humans category 2B. Recent researches conducted over the past 6 years related to ochratoxin toxicity encompassed the identification of factors involved in carcinogenesis and provided strong evidence to a reclassification of the Group 2B into the Group 2A probably carcinogenic to human beings [ 1 , 4 , 20 ].

Among the species of Penicillium , P. Another species of Penicillium produced from ochratoxin A is P. This mycotoxin is often found in animal feed and food as wheat, rye, coffee, nuts, and, at a lower degree, grapes, raisins, wine, or products derived from pork. There have been reports of this mycotoxin detected in blood and milk breast of individuals exposed to its ingestion [ 1 , 2 , 3 , 4 ].

The levels can accumulate in the tissues of the body and fluids of human beings or animals who consume contaminated food. Evidence shows that ochratoxin A is slowly eliminated from the body [ 17 , 25 ]. The structure of these toxins is derived from L-phenylalanine, which makes it a potent inhibitor of the enzyme phenylalanine-RNAt synthase, responsible for the synthesis of proteins of high turnover rich in phenylalanine—a functional role for kidney homeostasis.

In addition, it interferes in the lipid peroxidation causing damages to the DNA and oxidative stress. Therefore, it is suspected that ochratoxin A is one of the cancer-causing agents in the urinary tract as well as related to the damages to kidneys occurred in Eastern Europe.

Researches indicate that practically all Europeans have some ochratoxin concentration in their blood. Human exposition to ochratoxin occurs primarily from brown bread. In some parts of Europe, the most significant exposition derives from the consumption of animal products, especially those formulated based on pig blood [ 32 , 33 ]. The meeting of the Committee of Specialists on Agricultural Contaminants in food European Commission, DG Health, and food safety has been considering establishing limits to herbal teas, infusions, and baking [ 32 ].

Even though ochratoxins B and C are hepatotoxic, immunotoxic, teratogenic, and genotoxic, maximum tolerable limits are yet to be established regarding these toxins [ 34 , 35 ]. Patulin polyketide lactone 4-hydroxy-4H-furo 3. Food which are more susceptible to contamination by patulin in human diet are apples and by-products puree and juices.

Even though contamination with patulin is mainly associated with areas of contaminated tissue, it can penetrate around 1 cm in healthy regions of the fruit [ 1 ]. Patulin has been reported as mutagenic, neurotoxic, immunotoxic, and genotoxic and to cause gastrointestinal damages in rodents.

There is also some concern that similar effects may occur in humans through a long-term consumption of food and beverage contaminated with this mycotoxin. The IARC classified patulin as Category 3, non-classifiable regarding its carcinogenicity to human beings. Although some limits have been established, some countries, such as Pakistan, do not have any specific legislation for this toxin [ 36 ].

Trichothecenes are a group of secondary metabolites produced by fungi belonging to the genus Stachybotrys and mainly Fusarium , in which F. The group of trichothecenes is composed of over mycotoxins and carries this name because of their chemical structure constituted of a ring with tetracyclic skeleton 12,epoxitrichothecenes.

They also present varied ligand assembles, which provides toxicity. According to the IARC, DON is classified in level 3, that is, it does not represent a risk of cancer induction, although co-occurrence with aflatoxin may increase aflatoxin carcinogenicity. DON can also coexist combined with zearalenone [ 1 , 2 , 37 ].

Despite the existence of a relatively large amount of different trichothecenes, their natural occurrence in food and feed is mainly related to nivalenol, deoxynivalenol, toxin T-2, diacetoxyscirpenol, and less often furarenone-X, toxin HT-2, and neosolaniol. DON is probably the most largely distributed mycotoxin in food and feed often detected in wheat, barley, rye, malt, oat, maize, and consequently products derived from these cereals, such as flours and beers, and less often rice, sorghum, and triticale.

It is a heat-resistant toxin which is not altered during food processing, in addition to being stable over long storage periods [ 37 , 38 ].

Discovered in the early s, DON is also popularly known as vomitoxin for its acute effect on the ingestion of high doses causing symptoms similar to enterotoxins of Staphylococcus aureus and Bacillus cereus , such as nausea, vomit, abdominal pains, diarrhea, leukopenia, bleeding, and even death in humans and animals [ 37 , 38 ]. Pig is the most sensitive animal to DON, and the chronic effects of ingestion of contaminated feed result in reduced weight gain and growth, infertility, including the birth of animals with malformation, and miscarriage.

Birds are more tolerant than pig, and the effects of intoxication are lower quality and weight of the eggs produced.

Cattle are more tolerant, possibly due to the toxin degradation in secondary metabolites in the rumen. The effects in cattle include lower feed consumption and conception rate in addition to reduced milk production [ 2 , 37 ].

The European Union, in turn, proposes 0. Also known as toxin F-2, it is an estrogen produced mainly by F.

It is commonly found in several cereals, such as wheat, barley, sorghum, and mainly maize [ 6 ]. Zearalenones are considered micro-estrogenic due to their capacity to hamper the effect of steroid hormones interfering in human and animal reproductive capacities. It also influences the production of testosterone, progesterone, and estradiol.

Zearalenone is able to imitate the activity of estrogen in the reproductive tract, including accessory glands, such as the prostate [ 40 , 41 , 42 ]. It causes hyperestrogenism in pig, whose symptoms are swelling and redness of the vulva and hyperdevelopment of the uterus and mammary glands. In addition to present significant effects on the increase of endometrial secretions and synthesis of uterine proteins and higher weight of reproductive organs [ 31 ].

Birds are more resistant to intoxication by zearalenone, but the many associations of fusariotoxin with other mycotoxins can result in severe losses.

The production of zearalenone may occur either in the field or post-crop in inadequate storage conditions high moisture. The detection of this mycotoxin in bird feed has been considered a biomarker for other toxins belonging to the genus Fusarium [ 31 ]. Despite some evidence, the IARC assessed the carcinogenicity of zearalenone and found it to be a possible cancer-causing substance to humans.

Zearalenone residues do not seem to be an issue after consumed. They were discovered in and described as fumonisins B1, B2, and B3, in which B1 occurs more frequently. They are highly water-soluble unlike other mycotoxins and do not have an aromatic structure or a single chromophore to analytically facilitate its identification, therefore being difficult to identify through ultraviolet spectrum [ 25 ]. These substances are produced by several species of the genus Fusarium , especially by Fusarium verticillioides previously classified as F.

Other species, such as F. Fumonisins have been found as a common contaminant in maize-based food and feed. When ingested, fumonisins present low bioavailability and are rapidly metabolized and excreted. The carcinogenic nature of fumonisins does not seem to involve an interaction with DNA.

Their mode of action is related to their toxicity in the interference of the biosynthesis of sphingolipid, which are very important to maintain the integrity of the cell membrane, regulation of receptors of cell surface, ion pump, regulation of growth factors, and other vital systems for the functioning and survival of the cell. In addition, fumonisins are potent immunosuppressant agents and can enhance the susceptibility to diseases [ 38 , 39 , 40 , 41 , 42 , 43 , 44 ].

The main ochratoxin A producers, A. Penicillium verrucosum also produces ochratoxin A but occurs only in cool temperate climates, where it infects small grains. It has recently been shown that Aspergillus niger also produces fumonisins, and several commodities may be affected. Also included is a short section on Claviceps purpurea, which produces sclerotia among the seeds in grasses, including wheat, barley, and triticale.