Microbial damage and mutagenesis in cellulase-producing Aspergillus niger A32 induced by direct cold atmospheric...

In this study, we examined the effects of direct cold atmospheric plasma (CAP) exposure on microbial damage and mutagenesis in Aspergillus niger A32 for food industry applications. CAP generated at 15, 20 and 25 kV discharge voltages was selected for treating A. niger; the results showed that 75 % lethality and the highest positive mutation rate were obtained at 20 kV discharge voltage. The mutant strain A32-C10 displayed significant increases in enzyme activity compared with those in the controls: β-glucosidase at 40.69 U/mL (57 % increase), filter paper-degrading enzyme at 29.21 U/mL (30 % increase), and endo-cellulase at 14.09 U/mL (35 % increase). Scanning electron microscopy revealed severe physical damage to conidial heads and mycelium, including disrupted cell integrity and rough, irregular surfaces. Transmission electron microscopy showed substantial inner membrane damage and visible exudate after CAP treatment. Whole-genome resequencing of A32-C10 revealed 151 single nucleotide polymorphisms and 54 insertion-deletion mutations. Gene Ontology analysis indicated involvement of the mutated genes in transcription regulation, mitosis, signal transduction, and redox homeostasis. Therefore, direct CAP exposure induced significant physical oxidative damage to A. niger and effectively induced mutations. CAP thus emerges as an efficient, safe physical mutagen with promising applications in microbial breeding for the food industry.