A tandem conversion process for the synthesis of polyitaconic acid from glucose in the Aspergillus terreus culture.

Abstract

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 N₂ gas purging resulted in that the IA conversion, and the weight-averaged molecular weight (Mw) and the molecular weight distribution (MWD) of the synthesized polyitaconic acid (polyIA) were 11.5%, 79.8 × 10³ g/mol, and 1.26, respectively. The respiration by the IA producer itself was used to remove the residual oxygen in the flask by sealing after the IA production. Colorimetric evaluation with a redox indicator, resazurin, revealed that an anaerobic condition which is suitable for the IA polymerization can be accomplished by just incubation for 1 day after the sealing. The synthesis of polyIA from glucose in the same flask with 4mTHP was demonstrated, resulting in that the IA conversion, and Mw and MWD of the synthesized polyIA were 13.8%, 9.1 × 10³ g/mol, and 1.24, respectively, when 47.1 g/L (362 mM) IA was produced by the extraction for 3 days. To our knowledge, this is the first demonstration of radical polymerization of vinylidene monomer in microbial cultures.