2.2. Microorganism and inoculum
Strain JMU-TS528 was isolated from the soil around a pile of
rotted tea stalks in Anxi County (Fujian Province, China) and
identified to be a strain of A. niger by both morphological and genetic
methods. In brief, its mycelium and spore were identical to
characteristics of a typical A. niger. After comparison with the NCBI
database, its 28S ribosomal RNA sequence (Accession number:
JQ072028) was 99% homologous with the 28S ribosomal RNA genes
of ten A. niger strains, including IFM 54309 (Accession number:
AB363747), NJA-1 (Accession number: KJ365316) and KAML02
(Accession number: KC119204). It was preserved on potato
dextrose agar (PDA) slants (the medium was purchased from
Sinopharm Chemical Reagent Co., Ltd) at 4 C and subcultured
every three months. For the preparation of inoculums, the strain
was cultured on PDA slants at 30 C for 96 h. Thereafter, the spores
were washed and diluted to OD600 0.3 in a 0.75 g/100 mL NaCl
solution, which made a spore suspension at concentration of
1 109 CFU/mL.