THE OCCURENCE OF OCHRATOXIN A AND CYCLOPIAZONIC ACID IN MAIZE AND SORGHUM GROWN IN MICROCLIMATIC ZONES OF NIGER STATE

ABSTRACT

Mycotoxigenic fungi and their associated mycotoxins remain a significant threat to growers, consumers, and food regulators. They damage the quality of agricultural crop commodities and impact negatively on food safety. The aim of the study was to determine the occurrence of Penicillium fungi and two mycotoxins in of maize and sorghum in Niger. Sixty-four (64) composite samples (CS) of different varieties of maize and sorghum were collected from stores and markets located in four microclimatic zones of Niger state. Standard procedure was used to isolate Penicillium spp. Ochratoxin A (OTA) and Cyclopiazonic acid (CPA) were extracted and quantified by Enzyme-Linked Immunosorbent Assay (ELISA) and High Performance Liquid Chromatography (HPLC) respectively. The risk assessment as a result of consumption was also determined. The fungi isolate from the samples were: P.  verrucosom, P. griseofulvum and P. chrysogenum. The occurrence of Penicillium spp is highest in market maize samples (15.8 %) from wet zone and store samples in dry zone while sorghum had the highest prevalence (16.7 %) in stores sample from driest zone. The OTA was detected in 89.1% of both maize and sorghum samples at level of 1.799– 75.462 μg/Kg and 0.297 – 49.344 μg/Kg respectively. The CPA was detected in 45.3 % of both maize and sorghum samples at levels of 1.002 – 419.248 μg/Kg and 0.205 – 79.981 μg/Kg respectively. The contamination of the samples collected with OTA had the highest concentration in yellow maize collected from Magama market with 75.462 μg/Kg while the lowest concentration was found in white sorghum collected in Suleja store with the concentration of 0.297 μg/Kg. The co-occurrence of OTA and CPA was high in Magama store with 75.0 % and lowest in Bosso market with 25.0 %. The Estimated Daily Intake (EDI) for male was 0.021 – 0.111 μg/Kg and was 0.020 – 0.423 μg/Kg for female and the Tolerable Daily Intake (TDI) for OTA was 0.014 μg/Kg. there is a health risk to consumers of maize and sorghum due to the contamination of the samples with OTA and CPA in these study areas. Hence, this study advise that consumers of maize and sorghum should ensure proper cooking to reduce the health risk posed by these contaminants.

CHAPTER ONE

1.0   INTRODUCTION

1.1   Background of the Study

Mycotoxins are ancillary extrolites of certain fungi with low molecular weight manufactured in agricultural products exposed to harsh climatic conditions and these substances are toxin of various degrees (Agriopoulou et al., 2020). The production of toxin on crops by fungi is affected by atmospheric factors both in the field crops and stored crops. The contamination of mycotoxins in crops cannot be avoided and predicted, which present an exclusive challenge in the safety of food (Park and Stoloff, 1989; FAO, 1997). There is an increase in knowledge rate on mycotoxins and more discovery of mycotoxins co-contamination in food crops. Therefore, certain syndromes in animals are caused by mycotoxins which bears a strong relationship between the toxins and the resulted diseases (Gentles et al., 1999).  Even though specific evidences on the grounds of mycotoxins causing certain human diseases are inadequate, the potential risk of the dietary exposure in consumption of contaminated crops with mycotoxins should not be undermined. Ismaiel and Papenbrock (2015) reported that when the mycotoxins are present and there are no visible symptoms of a particularly disease, the plants physiology can still be slightly affected.

In 2017, the United Nation Population Division (UNPD) estimated a rise in world population by 2050 to be 9.8 billion people (Cumagun et al., 2019). Though the available earth’s resources, can basically cater for 10 billion people leading to swift diminution of such food supply leading to great shortage. Biotechnology’s techniques employed in agriculture and crop sciences will help in upsurge of production of food crops through the refining of the varieties of crops which possess high-yielding, drought-tolerant, ability and crops that opposes the infestation of pest and proliferation of diseases. Another approach in the reduction of food shortage is by circumvention of forfeiture of the yield of crop brought about by biotic and abiotic factors known to prevent the current food supply. In the framework of the safety and security of food crops, the worldwide deleterious effect of fungi that are toxigenic need to be taken seriously. The economics of such contaminated crops with these mycotoxins and also its negative health implication cannot be ignored. (Cumagun et al., 2019). The present of these toxigenic fungi on cereals products have huge possible effect to the populace both economically and likewise in health (Milani, 2013). Fungi are plant pathogens that exist all around us which serve as a huge spoilage agent of foods and feedstuffs as indicated by Makun et al. (2010).

These toxins by fungi are produced by some genera of fungi such as Penicillium, Fusarium or Aspergillus that grow on cereals which include the following: wheat, maize, oat, sorghum, groundnuts, legumes likewise oilseeds. The production of mycotoxin by fungi are determined by varied conditions such as biotic factors, harvesting, storage and processing conditions and the most significant factors is the climate. The biosynthesis of toxins, particular on cereal crops, is extremely dependent on physical conditions (for instance humidity and suitable temperature) the crops are exposed to, before harvest and after harvest. Therefore, when alteration of weather conditions occurs, the generation of mycotoxins will be affected due to the fact that fungi are climate-dependent (Milani, 2013).

The fungi Penicillium is an enormous and most imperative genera of fungi among other microorganisms, with wide-reaching of more than 400 designated species. The name Penicillium is derived from “Penicillus” – Latin, and that denotes its conidiophores brush-like appearance with the likeness of a painter’s brush (Yin et al., 2017).

Penicillium is a very recognized and among the communal fungi found in a diverse range of habitats, which include the following: air, soil, environment within the house, food crops and vegetation. These fungi possess global distribution and a huge economic influence on the lives of human beings. Its main function in nature is the decomposition of organic materials, where species cause devastating rots as pre- and postharvest pathogens on food crops (Visagie et al., 2014, Park et al., 2019). The genus Penicillium is common in different environments such as soil, plant, air and food products. Some species can be used in cheese production, antibiotics production while others are pathogens for human. However, Penicillium is an important genus because of its commercial and industrial uses such as anti-tumoral, anti-fungal and anti-viral compounds, and in the production of enzymes (Kolanlarli et al., 2019). They also synthesis a diversity of bioactive metabolites with suitable industrial application, which include antibacterial agents, mycotoxins, and enzymes (Park et al., 2019).

Mycotoxins have triggered foremost epidemics among mankind and other animals in time past. The high ranking epidemics which include ergotism, which killed several thousands of people in Europe in the last millennium; alimentary toxic aleukia, which accounted  for the death of not least than 100,000 people of Russia between 1942 – 1948; stachybotryotoxicosis in the USSR, lead to death of tens of thousands of horses in the 1930s; and aflatoxicosis in the United Kingdom (UK) , which lead to the fatality of 100,000 young turkeys in 1960 and also had resulted to casualties in other living organisms as well as man (Pitt, 2000). Ochratoxin A (OTA) is detected in grain crops, chiefly finely ground cereal grains. OTA is also detected in traded commodities such as solid food made from milk (cheese) and others animals’ products which originated from the consumption of cereals contaminated with mycotoxins (Milani, 2013). Cyclopiazonic acid (CPA) occur naturally in groundnuts, maize, cheese, processed

products from tomato, and also animal products like poultry eggs, meat and milk of animals that were previously served by feeds contaminated with mycotoxins (Lavkor et al., 2017). The co-occurrence of mycotoxin contamination of groundnut in Nigeria was reported to include CPA, moniliformin, aflatoxins (AFB1, AFB2, AFG1, AFG2 and AFM1), nivalenol, OTA and beauvericin. The samples with higher concentrations were detected with CPA above other mentioned mycotoxins (Oyedele et al., 2017 as cited by Ostry et al., 2018).

Niger State has four microclimatic zone as follows: wettest zone (zone 1), wet zone (zone 2), dry zone (zone 3) and driest zone (zone 4) where cereal is cultivated. These climatic conditions can promote the infestation of fungi and lead to mycotoxins contamination in maize and sorghum commodities. Nigeria is the largest producer of Maize in Africa and Niger State is one of the five states leading in the maize production (Odusanya, 2018). On the other hand, Nigeria is the biggest producers of sorghum among the West Africa countries with about 71% and third-largest world producers of sorghum (OECD/FAO, 2019).

1.2       Statement of the Research Problem

The proliferation of mycotoxigenic fungi and the respective mycotoxins produce by such fungi stays a colossal hazard to growers, consumers, and regulators of food. They mutilate the essential property of crop products and badly effect the safety of food. The contamination of food crops and forage with mycotoxin is a problem that affect both Nigeria and much larger scale globally (Cumagun et al., 2019).

Mycotoxins remain a crucial worldwide issue on food safety, even the Food Agriculture Organization (FAO) made a statement that crops products which are contaminated by fungi and mycotoxins with about 25 % will result to a lose in the economics of the crop amounting in one thousand million of dollars (FAO, 2004 as cited by Wolf and Schweigert, 2018).

Mycotoxins naturally occur in peanuts, sunflower seeds, Kodo millet, cheers and cereals like maize and sorghum. CPA is poisonous in diversity of living organisms with much consequences in human toxicity – Kodua poisoning (Ostryl et al., 2018). The aflatoxins and CPA co-occurred in agricultural products at the same time. For example, CPA was found to be present in aflatoxicosis, even though it might may be concealed, for instance, the peanut meal that caused Turkey “X” disease were isolated both with aflatoxins and CPA which had led to the loss of above 100,000 turkeys. It is the basis for tissues death in vital organs involving in metabolic process like the kidney and the liver (Lavkor et al., 2017).

Ochratoxin A (OTA) rank among the highly lethal to warm blooded vertebrate animals like mammals, providing a grounds for diverse lethal effects including toxicity on kidney (hepatotoxicity), agent affecting embryo or fetus  (teratogenicity), and  agents that cause mutation (mutagenicity), resulting in specific health disorder such as inflammation of liver, excessive bleeding, excessive fluid in body tissues, suppression of a healthy immune response, malignant tumor in the liver, carcinoma in the throat passage, and failure in the function of kidney (Santos et al., 2001 as cited by Reddy et al., 2010; Milani, 2013). The contact of people and other animals to food contaminated with mycotoxins is predominantly a tropical region problem (Reddy and Raghavender, 2008). To scrutinize the lethal consequences of OTA which is an acute toxin and CPA which is chronic toxins on human beings and other organisms, it is vital to appreciate the level of these mycotoxin contaminating foods globally so as to ascertain and carry out the needed supervision strategies. For that reason, the level of contaminations of OTA and CPA detected in the diversity of food crops nationally and globally require level of review, along with health implications in human health, together with a specific emphasis on tropical regions like Nigeria (Reddy et al., 2010). The synthesis of OTA and CPA by Penicillium spp activities, results to crops contamination with such toxins in the course of storage within humid conditions. As long as the field crop turn out to be infested with the growth of fungal this growing situation will be maintained if the humidity and temperature favors the proliferation during storage of crops and processing of food (Reddy et al., 2010).

1.3      Justification for the Study

Presently, the account on the bid to measure the extent of CPA contamination on food crops are solely minimal. (Ostry et al., 2018). There are no enough statistical reports on CPA occurrences in maize and sorghum grains in Niger. The problems of cereal contamination with mycotoxin by fungi can be controlled and monitored by careful commodity screening and provision of improved storage conditions (Lavkor et al., 2017). The cultivation of maize and sorghum in Niger state is highly favored among others cereal grains, this therefore prompt the need for the choice of these cereals for monitoring of mycotoxins contamination. Also, the literatures on the co-occurrences of OTA and CPA in maize as well as sorghum samples each is considered to be very low since Penicillium spp can produce these mycotoxins (Makun et al., 2010). The samples collected from stored and market are prompt to be infested by storage fungi, such as Penicillium and aspergillus and therefore the mycotoxins are produced (Adam and Moss, 1999). Therefore, co-occurrences of OTA and CPA will result to multiple health problems in the animals and human beings that feed on such contaminated cereals. The risk assessment on human being on the possibility of been at higher risk by multi-mycotoxins is not fully carried out due to inadequate food consumption data, and this study is providing such data for Niger state (Viegas et al., 2011).

1.4       Aim and Objectives

1.4.1    Aim

The aim of this study includes determining presence of Penicillium fungi, ochratoxin A and cyclopiazonic acid as detected in maize and sorghum from the four microclimatic regions of Niger State.

1.4.2    Objectives of the study

These objectives include, to:

i.      Isolate and identify Penicillium species both morphologically and microscopically from the varieties of maize and sorghum grains.

ii.     Analyse the naturally occurring OTA and CPA extracted from maize and sorghum using Enzyme-Linked Immunosorbent Assay (ELISA) and High Pressure Liquid Chromatography (HPLC).

iii.   Assess the dietary exposure risk from the consumption of maize and sorghum from the. four microclimatic zones in Niger State.

iv.    Determine the co-occurrence of OTA and CPA in maize and sorghum varieties from the study area.

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