In this study, a bio-based vinylidene monomer, itaconic acid (IA), produced by a fungus Aspergillus terreus NBRC 6123 was polymerized in the culture. The inhibition of IA polymerization by the culture components was eased by extraction with 4-methyltetrahydropyran (4mTHP). The extraction with 4mTHP for 4 days under aerobic condition resulted in IA production at 67.9 g/L (522 mM) in the organic phase from 180 g/L glucose. Interestingly, 4mTHP did not affect to the glucose consumption and respiration of A. terreus. IA polymerization in 4mTHP for 72 h using 400 mM IA and 1 mM 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) as a radical initiator under anaerobic condition by N