The current study was designed to improve riboflavin production utilizing the filamentous fungus Aspergillus terreus. The effect of different nutritional and environmental factors was carried out by applying onefactor- at-a-time method. The selected high producer fungal strain was identified on the bases of the sequences of the gene encoding 18S rRNA and designated as A. terreus ASU1 (KP793450). In order to investigate the quantitative, optimal levels and the reciprocal interactions between five main medium components, response surface methodology
(RSM) was subsequently employed. The results proved
that optimal concentrations for enhancement of riboflavin production were: corn starch 30 (g/l); tryptone 0.5 (g/l) and 1 (g/l) for each glycine, KH2PO4 and MgSO4. The maximum riboflavin production of 344.60 mg/l (predicted 342.86 mg/l) was determined under the optimal conditions and the regression analysis (R2) of RSM showed 97.7 %. In
comparison to the production of original level (63 mg/l), 5.4-fold increase had been obtained.