BIOSECURITY FOR REDUCING OCHRATOXIN A PRODUCTIVITY AND THEIR IMPACT ON GERMINATION AND ULTRASTRUCTURES OF GERMINATED WHEAT GRAINS

Journal of Microbiology, Biotechnology and Food Sciences El-Taher et al. 2012 : 2 (1) 135-151 REGULAR ARTICLE BIOSECURITY FOR REDUCING OCHRATOXIN A PRODUCTIVITY AND THEIR IMPACT ON GERMINATION AND ULTRASTRUCTURES OF GERMINATED WHEAT GRAINS Eman M. El-Taher1 , Abd El- Ghany T.M* 2., Alawlaqi, M.M3., Mona S. Ashour1 1 Regional Center for Mycology and Biotechnology, 2Botany and Microbiology Dept., Faculty of Science, Al-Azhar University, Cairo, Egypt. 3Biology Department, Faculty of Science, Jazan University, KSA. * Corresponding author, Tarek M. Abdelghany e-mail: ABSTRACT Ochratoxin A (OTA) is a secondary metabolite of some fungi that causes very serious problems for plants, animals and humans. Various microorganisms such as bacteria and microscopic fungi have been tested for their abilities to prevent ochratoxin A contamination or detoxify foods. In this study, Saccharomyces cerevisiae and Lactobacillus bulgaricus reduced OTA production by Aspergillus ochraceus to 40.88 µg/ml ( productivity 60.69% ) and 13.80 µg/ml (productivity 20.48% ) respectively compared with the control (67.35 µg/ml) (productivity 100%). The results clearly indicated that the seed germinibility in the presence of OTA was decreased with increasing concentration, whereas the germinibility was uncompletely ceased at high concentration (67.35 µg/ml) of OTA. The maximum amount of germination was observed in control (without OTA treatment) and at low concentration (13.80 µg/ml) within 4 days. Antioxidant enzymes catalase and peroxidase decreased in germinated grains treated with OTA. Catalase was 18.12 U/ml in grains treated with low concentration (13.80 µg/ml) of OTA while at high concentration (67.35 µg/ml), it was 12.23 U/ml compared with the control (20.33 U/ml). On the other hand, peroxidase decreased only in germinated grains treated with high concentration of OTA. The ultrastructural studies 135 JMBFS / El-Taher et al. 2012 : 2 (1) 135-151 indicate that there were dramatic differences between the cells of root system of wheat seedlings of grains treated and untreated with the OTA. Cell ultrastructures of treated grains with OTA showed that the cytoplasmic membrane collapses away from the cell wall. Plasmodesmata threads were appeared in untreated cells but not formed in treated cells. Key words: Biosecurity, ochratoxin A, productivity, wheat grains INTRODUCTION Ochratoxins are worldwide spread secondary metabolites synthesized mainly by some toxigenic species of Aspergillus and Penicillium (Sedmikova et al., 2001; Bayman et al., 2002; Magan and Aldred, 2005). P. verrucosum is the major OTA-producing fungus in northern Europe, while A. ochraceus is more important in warmer climatic zones (CairnsFuller et al., 2005). More Aspergillus species have been found to produce OTA, for example A. melleus, A. sulphureus, A. alliaceus, A. sclerotiorum (Bayman and Baker, 2006), A. albertensis, A. lanosus (Palumbo et al., 2007). Ochratoxin A (OTA) is important because of the contamination of agricultural products including cereals and grains and influence chronic human exposure (Alexa et al., 2008; Dehelean, 2011). Natural occurrence of OTA in maize and maize-based products is a world wide problem (Duarte et al., 2010). Maize kernels are a good substrate for mould infection and production of mycotoxins harmful to both humans and animals. A. niger is frequently isolated from maize (Magnoli et al., 2007; Shah et al., 2010) and a high incidence of A. carbonarius has been also reported (Shah et al., 2010; Alborch et al., 2011). Both species could be a source of OTA in maize and other food products in both tropical and subtropical zones of the world (Palencia et al., 2010). The highest reported occurrences of OTA contamination have been found in cereal grains, and to a lesser extent in grapes, wine, grape juice and dried vine fruits (Clark and Snedeker, 2006). Fungal invasion and mycotoxins contamination of agricultural products lead to losses in terms of quantity, market value, quality of food and feed production due to changes in colour, texture and taste (Mutegi et al., 2009) and reduction of seed germination (Negedu et al., 2010), energy and nutritional value changes in terms of loss of carbohydrates, proteins, amino acids and vitamins and increases in fatty acids may also occur (Negedu, 2009). Many species of bacteria, fungi and yeasts have been shown to enzymatically degrade mycotoxins (Bata and Lasztity, 1999). Bejaouii et al. (2004) suggested that oenological 136 JMBFS / El-Taher et al. 2012 : 2 (1) 135-151 strains of Saccharomyces yeasts can be used for the decontamination of OTA in synthetic and natural grape juice. Several bacterial and fungal strains belonging to Streptococcus, Bifidobacterium, Lactobacillus, Butyrivibrio, Phenylobacterium, Pleurotus, Saccharomyces, Bacillus and Acinetobacter genera and certain fungi belonging to Aspergillus (A. fumigatus, A. niger, A. carbonarius, A. japonicus, A. versicolor, A. wentii and A. ochraceus), Alternaria, Botrytis, Cladosporium, Phaffia, Penicillum and Rhizopus (R. stolonifer and R. oryzae) genera, are able to degrade OTA in vitro up to more than 95% (Abunrosa et al., 2006). Some microorganisms have been found to control Aspergillus, Penicillium infections and OTA production (Ciconova et al., 2010). For example, lactic acid bacteria produce antifungal substances. Corsetti et al. (1998) found antifungal effect of the mixture of short-chained organic acids that were produced by Lactobacillus (Lb.) sanfranciscensis. This bacterium inhibited the growth of A. niger and P. expansum on malt agar medium. Cell-free supernatant from Lb. casei inhibited spore germination of the investigated Penicillium spp. on potato dextrose agar medium. Also Bacillus subtilis produced a peptidolipid that inhibited A. ochraceus (Klich et al., 1991). Other Bacillus sp., B. thuringiensis used as a commercial insecticide during the cultivation of wine grapes inhibited the growth of A. carbonarius on potato dextrose agar medium (Bae et al., 2004). Masoud et al. (2005) found that Pichia anomala and Pichia kluyveri inhibited the production of OTA by A. ochraceus on malt extract agar medium and on coffee agar medium. The competing microbes may enhance or hinder the formation of mycotoxins by changing the metabolism of the producing organisms, by competing for the substrates by changing the environmental conditions making them unfavourable for mycotoxin production or by producing inhibitorial compounds (Ritieni et al., 1997). The phytotoxic effect of many secondary metabolites produced by fungi has been shown through biotests in plants (Kachlicki and Jedrycka, 1997). Changes in the plant cell structure and alterations of the cytoplasm were discernible after root treatment with toxin solutions at the higher concentration (250 μg/ml). The cells appeared turgid, but with very extensive plication of cell membranes and part of the cell walls, and having numerous vesicles in th (...truncated)