IOSR Journal of Environmental Science, Toxicology and Food Technology (IOSR-JESTFT) e-ISSN: 2319-2402,p- ISSN: 2319-2399.Volume 13, Issue 11 Ser. I (November. 2019), PP 01-07 www.iosrjournals.org DOI: 10.9790/2402-1311010107 www.iosrjournals.org 1 | Page Modulation of Aflatoxin Production by Interaction of Aspergillus Species from Eastern Kenya Micah Kipkemboi Lagat 1 , Faith Jebet Toroitich 2* , Meshack Amos Obonyo 1 , Huxley Mae Makonde 3 1 Department of Biochemistry and Molecular Biology, Egerton University, P. O. Box 536 -20115 Egerton, Kenya. 2 Department of Biological Sciences, Egerton University, P. O. Box 536 -20115 Egerton, Kenya. 3 Department of Pure and Applied Sciences, Technical University of Mombasa, P.O. Box 90420 - 80100 G.P.O Mombasa, Kenya. *Corresponding Author: Faith Jebet Toroitich Abstract: Aflatoxin contamination of grain has continued to pose a significant threat to sustainable food security and trade worldwide. In the field, there are incidences of varying contamination levels in grain within the same niche. We hypothesize that the variation could be due to fungal species interaction at the kernel level. Seventeen isolates (14 Aspergillus flavus and 3 Aspergillus parasiticus) from Eastern Kenya were selected and confirmed for toxigenicity using Dichlorvos-Ammonia method, then cultured based on their isolation frequencies and co-existence in nature. The fungi were co-cultured using maize kernels as growth substrate, which was then used to estimate aflatoxin produced in a competitive ELISA. A one-sample two-tailed t-test was carried out to determine the degree of significance in aflatoxin production. Eight isolates were non-toxigenic, while nine were toxigenic. When co-cultured with some non-toxigenic isolates such as A. parasiticus (2EM0601), the most toxigenic A. flavus isolate (1EM1901) significantly increased aflatoxin production, while it reduced with others. These observations warrant investigation on the interaction of Aspergillus species in culture especially given their diverse toxigenic potential. We concluded that colony-mediated aflatoxin production could explain the variations of toxin levels observed in freshly collected field samples. Keywords: Toxigenicity; aflatoxins; fungal interactions; Aspergillus; Dichlorvos-Ammonia --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 08-04-2019 Date of Acceptance: 13-04-2019 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction Aflatoxins are potent hepatotoxic and carcinogenic metabolites produced by fungi of the genus Aspergillus. The important members of this group include A. flavus and A. parasiticus, which contaminate various oil-rich seeds including maize (Zea mays), groundnuts (Arachis hypogaea) and cotton (Gossypium hirsutum) [1]. The consumption of food with high levels of aflatoxins is detrimental to both human and animal health leading to acute and chronic aflatoxicosis. Kenya is now ranked high among countries with recurrent and severe episodes of outbreaks of aflatoxicosis. The most severe case was reported in the Eastern part of the country, where it resulted in 125 fatalities in 2004 [2]. Subsequent surveys over three years found that aflatoxin levels were lethal and as high as 38,000 ppb [3]. The perennial high levels of aflatoxins recorded in Kenya have aroused research efforts towards their management [4]. Biological control using non-toxigenic Aspergillus flavus to compete against toxigenic species has shown great potential in cotton [5]. The non-toxigenic A. flavus has subsequently been formulated into different commercial products AflaSafe™ and Aflaguard® for use in peanut and maize production in Africa [6, 7]. The current efforts are geared towards the development of biological control agents for the Kenyan environment. However, and an important prerequisite is to understand the nature of interactions among different strains of A. flavus and A. parasiticus. It has been recorded that aflatoxigenesis is dependent on various factors including temperature, moisture, pressure, and competition by colonies [8, 9]. The current class of biocontrol agents being deployed work based on ‘competitive exclusion’ where one strain out-competes another for nutrient acquisition, reproduction, and space [10]. We hypothesize that the interaction between strains in section Flavi is mediated by contact between hyphae of the interacting species and possibly other unknown mechanisms. Such interactions influence aflatoxin synthesis either positively or negatively. In the selection of candidate strains for biocontrol, it is imperative to decipher the dynamics of species interaction and its effect on toxigenicity. The current study sought to establish the impact of interactions between the congeneric species of Aspergillus (A. flavus and A. parasiticus) previously isolated from a common niche [11].