Abstract
This study aimed to investigate the antagonistic effect of three strains of the genus Bacillus on toxigenic fungi contaminating food commodities, with emphasis on two ochratoxigenic isolates (A. ochraceus, A. westerdijkiae) and two aflatoxigenic isolates (A. flavus and A. parasiticus). In vitro studies were carried out using two different methods for cultivation tested bacilli with fungal isolates – coincubation and dual culture method. The most sensitive isolate was A. ochraceus by both used methods. B. mycoides (5.72 ± 6.4 mm) and B. subtilis (5.08 ± 2.84 mm) were able to inhibit its growth and sporulation during ten days of cultivation (both inhibited the sporulation of A. ochraceus 100%) in coincubation. The most effective in the dual culture method were B. subtilis and B. thuringiensis against A. ochraceus (growth inhibition rate 84.40%; 90.55%) and A. flavus (growth inhibition rate 91.54%; 92.43%). The most effective sporulation inhibitors were B. subtilis and B. thuringiensis, which completely inhibited the sporulation of A. ochraceus and A. parasiticus after ten days of coincubation. Likewise, all tested bacterial strains showed complete inhibition of ochratoxin A synthesis in A. ochraceus and A. westerdijkiae exposure to bacterial volatiles. So, the current study illustrated that strains of the genus Bacillus could significantly inhibit the growth, sporulation, and mycotoxin production of toxigenic aspergilli and showing the great potential as a biocontrol agent of pre- and post-harvest food diseases caused by microscopic filamentous fungi.
Highlights
Food spoilage, mainly microbial spoilage, is a major worldwide problem for the food industry, leading to the waste of edible foods and economic losses for producers and consumers (Lorenzo et al, 2018)
The Percentage of Mycelial Growth Inhibition (PGMI) of the tested species was calculated using the following equation: Contamination of food with various perishable microorganisms, mainly microscopic filamentous fungi, is a global problem that leads to large-scale economic losses
The second method was used to evaluate the antifungal activity of Bacillus spp. by the method of dual culture, where the tested bacilli were inoculated on one plate together with the fungi and were in contact with each other
Summary
Mainly microbial spoilage, is a major worldwide problem for the food industry, leading to the waste of edible foods and economic losses for producers and consumers (Lorenzo et al, 2018). To prevent the deterioration of food crops and foodstuffs by fungal contaminants and their mycotoxins and prolong the shelf life of the products, different methods are used to eliminate them This includes the use of fungicides, chemical preservatives, and various other chemical and physical methods. There are several mechanisms for the use of Bacillus species to control food fungal pathogens, including competition in space or nutrients, antibiosis, and induced systemic plant resistance (Lastochkina et al, 2019). One of these mechanisms, antibiosis, has been reported as an essential mechanism by which the genus.
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