This study evaluated the impact of seasonal and geographical variations on the toxigenicity of Aspergillus and Fusarium strains previously isolated from smallholder dairy cattle feeds and feedstuffs sampled during summer and winter in the Free State and Limpopo provinces of South Africa (SA). In total, 112 potential toxigenic fungal species were obtained and determined for their capability to produce mycotoxins on solid Czapek Yeast Extract Agar (CYA); followed by liquid chromatography-mass spectrometry (LC-MS/MS) analysis. Our result revealed that 41.96% of the fungal species produced their respective mycotoxins, including aflatoxin B₁ (AFB₁), aflatoxin B₂ (AFB₂), and zearalenone (ZEN), with higher levels of AFB₁ (0.22 to 1045.80 µg/kg) and AFB₂ (0.11 to 3.44 µg/kg) produced by fungal species isolated from summer samples than those in winter [(0.69 to 14.44 µg/kg) and (0.21 to 2.26 µg/kg), respectively]. The same pattern was also observed for AFB₁ and AFB₂ in Limpopo (0.43 to 1045.80 µg/kg and 0.13 to 3.44 µg/kg) and Free State (0.22 to 576.14 µg/kg and 0.11 to 2.82 µg/kg), respectively. More so, ZEN concentrations in summer (7.75 to 97.18 µg/kg) were higher than in winter (5.20 to 15.90 µg/kg). A similar observation was also noted for ZEN in Limpopo (7.80 to 97.18 µg/kg) and Free State (5.20 to 15.90 µg/kg). These findings were confirmed via Welch and Brown-Forsythe tests with significantly (p ≤ 0.05) higher mycotoxin levels produced by fungal strains obtained in samples during summer than those in winter. In contrast, the concentrations of mycotoxins produced by the fungal species from both provinces were not significantly (p > 0.05) different.

This study investigated 65 (35 in summer and 30 in winter) smallholder dairy cattle feeds from Free State and Limpopo provinces in South Africa from 2018 to 2019 for fungal contamination and assessed the impacts of seasonal variation on fungal contamination levels, isolation frequency, and diversity. Samples were examined for fungal contamination using macro- and microscopic approaches, and their identities were confirmed by molecular means. A total of 217 fungal isolates from 14 genera, including Aspergillus, Fusarium, and Penicillium, were recovered from feeds from both seasons. The most prevalent fungal species recovered were A. fumigatus and P. crustosum. Mycological analyses showed that 97% of samples were contaminated with one or more fungal isolates, with the summer fungal mean level (6.1 × 10³ to 3.0 × 10⁶ CFU/g) higher than that of feeds sampled during winter (mean level: 1.1 × 10³ to 4.1 × 10⁵ CFU/g). Independent sample t-test revealed that the isolation frequencies of the genera Aspergillus and Fusarium were significantly (p ≤ 0.05) higher in summer than winter, while Penicillium prevalence in both seasons was not statistically (p > 0.05) different. Furthermore, the Shannon–Weiner diversity index (H′) revealed a higher fungal diversity in summer (H′ = 2.8) than in winter (H′ = 2.1). This study on fungal contamination could be used for future fungal control and mycotoxin risk management in South Africa.

Contamination of agricultural products such as maize by fungi is a significant concern worldwide, as it can compromise food safety and quality. In recent years, the use of microorganisms as natural food preservatives has gained interest. Probiotic lactic acid bacteria (LAB) and their metabolites are considered a promising strategy to reduce fungal growth and limit other food contaminants. This study aimed to characterize, screen and compare the probiotic properties and antifungal activity of LAB of maize origin. A total of 23 LAB isolates obtained from untreated maize grains were identified through 16S rRNA gene sequencing as Weissella viridenscens (34.7%), Pediococcus pentosaceus (34.7%), Enterococcus durans (17.4%), Leuconostoc citreum (9%), and Enterococcus faecium (4.3%). All isolates demonstrated acid, phenol, and bile salt tolerance; surface hydrophobicity; and antagonistic activity against selected bacterial foodborne pathogens. Notably, Enterococcus sp. showed the strongest inhibitory activity against Escherichia coli ATCC 5211 (21 mm inhibition zone) and Staphylococcus aureus (17 mm inhibition zone), whereas Pediococcus sp. exhibited the highest antagonistic effect against Listeria monocytogenes (18.7 mm inhibition zone). Furthermore, E. durans and P. pentosaceus demonstrated the strongest antifungal activity, effectively inhibiting the growth of Alternaria tenuissima (F22FR) and Fusarium oxysporum (F44FR), respectively. Overall, all the LAB strains isolated from this study showed considerable potential for use in the food industry as probiotics, starter cultures for functional food fermentations, bio-preservatives and biocontrol agents against toxigenic fungi and pathogenic bacteria, with E. durans standing out for its exceptional performance. Future research will explore the ability of these isolates and/or their enzymes to degrade mycotoxins commonly found in maize, a staple food in many African countries.