Will climate change affect growth and ochratoxin A production of putative biocontrol knockout strains of Aspergillus carbonarius?

The research explored the effects of abiotic factors associated with climate change (CC) on the growth and metabolite production of wild-type Aspergillus carbonarius ITEM 5010 and three knockout mutants: one knockout in the first gene of the ochratoxin A (OTA) biosynthesis pathway (ΔotaA) and two in the veA and laeA genes (the latter knockout generated in this work) encoding VELVET complex proteins, which regulate metabolism. Variables examined were temperature (30 °C vs 37 °C), water activity (0.98 vs 0.90), and CO₂ levels (400 ppm vs 1000 ppm). Growth, OTA production, and other metabolites were evaluated on grape-based medium. The results showed that abiotic factors significantly influenced fungal growth and mycotoxin production, with a_w being the most critical parameter. At a_w 0.90, no growth was observed. A temperature of 37 °C combined with 1000 ppm CO₂ resulted in higher OTA production, indicating a greater health risk in predicted CC scenarios. Mutants of global regulatory factors showed altered metabolite production, with elevated OTA levels at 37 °C. The ΔotaA knockout mutant consistently showed no OTA production, suggesting its viability as a biocontrol agent under CC conditions. However, while OTA increased, other secondary metabolites, such as pyranonigrin A and kojic acid, decreased with rising temperatures in all strains. The research highlights the influence of abiotic factors related to CC on A. carbonarius growth and metabolite production, underlining the threat of increased mycotoxin production. This reinforces the need for resilient biocontrol strategies. The ΔotaA mutant has been identified as a potential biocontrol agent, demonstrating resistance to future environmental stresses associated with CC.