Preculture medium consisted of (g/L) glucose 50, urea 2, KH2PO4 0.6, MgSO4·7H2O 0.5,
ZnSO4·7H2O 0.11, and FeSO4·7H2O 0.0088. The medium pH (4.6) was not adjusted,
otherwise mentioned. The medium was sterilized in two parts to avoid the Maillard reaction
between the carbonyl group (>C=O) of glucose and amino group (−NH2) of urea. One part
without the glucose was heat-sterilized (20 min, 15 lb, 121±1 °C), while glucose was
sterilized separately (20 min, 15 lb, 110±1 °C). Sterilized medium was used for preculture
of R. oryzae to obtain the pelletized seed. Medium was inoculated with the spore suspension
(2 %, v/v). Precultures were carried out in 250-mL Erlenmeyer flasks with a final medium