The Effect of Lactobacillus plantarum on the Ochratoxigenic Potential of Aspergillus carbonarius at the Gene Expression Level

Introduction: From a food safety perspective, Ochratoxin A (OTA) remains a challenge in the continuous effort to eliminate toxins from the food chain. Aspergillus carbonarius stands among the dominant toxigenic producers in a variety of foodstuffs, including table grape berries.

Purpose:   In this work, the inhibitory effect of Lactobacillus plantarum against Aspergillus carbonarius was investigated in terms of anti-ochratoxigenic activity, along with of OTA-related gene expression.

Methods:  One wild fungal isolate and a reference strain of Aspergillus carbonarius were co-cultured with four bacterial strains of Lactobacillus plantarum on MRS agar plates, incubated at 30°C. Mycelia were collected for toxin quantification after 3 days growth. Gene expression of OTA biosynthetic key genes nrps and pks was monitored at the same time using Real-Time PCR.

Results: HPLC analysis of OTA presentedown-regulationd inter-strain differences among bacterial efficacy for toxin reduction. OTA production was decreased by 51-100%. Gene expression analysis showed differences between the fungal strains. In pks gene, up to three-fold down-regulation was observed in almost all bacterial treatments. In contrast, the nrps transcripts showed up to a three-fold down-regulation in the wild strain and up to a nine-fold up-regulation in the reference strain.

Significance: According to the above findings, the specific microbial strains have been proven to successfully control mycotoxin and, also, reveals a possible mode of action at the molecular level.