Twenty-eight fungal endophytes were recovered from the different parts of Ginkgo biloba and screened for their Taxol producing potency. Among these isolates, Penicillium polonicum AUMC14487 was reported as the potent Taxol producer (90.53 mg/l). The chemical identity of the extracted Taxol was verified from the TLC, HPLC, NMR, EDX, and FTIR analyses. The extracted Taxol displayed a strong antiproliferative activity against HEPG2 (IC50 4.06 mM) and MCF7 (IC50 6.07 mM). The yield of Taxol by P. polonicum was optimized by nutritional optimization with the Response Surface Methodology (RSM) using Plackett- Burman and Central Composite Designs. In addition to nutritional optimization, the effect of g-irradiation of the spores of P. polonicum on its Taxol producing potency was evaluated. The yield of Taxol by P. polonicum was increased via nutritional optimization by response surface methodology with Plackett-Burman and FCCD designs, and g-irradiation by about 4.5 folds, comparing to the control culture. The yield of Taxol was increased by about 1.2 folds (401.2 mg/l) by g -irradiation of the isolates at 0.5
0.75 kGy, comparing to the control cultures (332.2 mg/l). The highest Taxol yield was obtained by growing P. polonicum on modified Czapek’s- Dox medium (sucrose 40.0 g/l, malt extract 20.0 g/l, peptone 2.0 g/l, K2PO4 2.0 g/l, KCl 1.0 g/l, NaNO3 2.0 g/l, MgSO4. 5H2O 1.0 g/l) of pH 7.0 at 30.0 C for 7.0 days. From the FCCD design, sucrose, malt extract and incubation time being the highest significant variables medium components affecting the Taxol production by P. polonicum.