Optimization of the preparation of a spiny spore high-concentrated Aspergillus brasiliensis suspension

This work aimed to improve some steps of the existing guidelines of the European Standards to obtain an Aspergillus brasiliensis ATCC 16404 spore suspension with >75% spiny spores without mycelia and a concentration of at least 1.5 × 108 CFU ml-1. Several manufacturers' combinations of "strain/medium" were assessed in terms of yield of spiny spores. Criteria to establish success included (i) the growth over different times of incubation (4, 7, and 10 days); (ii) the performance of two different filtration devices (fritted filters and cell strainers); and (iii) the fungal spores susceptibility after 4 days of incubation versus 7 days of incubation against a peracetic acid-based disinfectant. The best combination was "Microbiologics strain/Oxoid MEA" with 88.33% of spiny spores already after 4 days, and no statistical differences (P < .05) in terms of growth in the three time points were highlighted (from 1.85 × 108 CFU ml-1 to 2.21 × 108 CFU ml-1). Cell strainers gave a spore suspension much more concentrated (3.31 times) compared to fritted filters. Furthermore, the 4-day-old spore suspension showed the same susceptibility to disinfection when compared to a suspension whose culture was incubated for 7 days.