Screening of A. oryzae and strain improvement by
UV mutagenesis for hyper production of acid protease
Screening of isolates for acid protease production was carried
out on enrichment media containing (w/v): yeast extract
(0.5%), polypeptone (1%), soluble starch (2.0%) and potassium
phosphate (0.27%). A potential strain was identified to produce
high levels of protease. In addition, the parent strain was
subjected to mutation by UV mutagenesis using an ultraviolet
germicidal lamp on a clean bench (Sanyo, Japan). Briefly,
conidia of A. oryzae RIB40 were spread into PDA plates and
after UV treatment, were incubated at 30 ◦C for 3 or 4 days
until the colonies appeared. Then any colonies showing morphology
different from that of the parent strain were picked
out, followed by inoculation and cultivation as a single colony
on a PDA plate. The resulting strains were subjected to acid
protease assay