The development of high-performance biobased polymers such as polyimides (PIs) is indispensable to establish a sustainable green society, but it is very difficult due to the incompatibility of their monomeric aromatic diamines with microorganisms. Here, we developed biobased PIs from bioavailable aromatic diamines, which were photodimers of 4-aminocinnamic acid (4ACA) derived from genetically manipulated Escherichia coli. These biobased PI films showed ultrahigh thermal resistance with T 10 values over 425°C and no T g values under 350°C, which is the highest value of all biobased plastics reported thus far. The PI films also showed high tensile strength, high Young's moduli, good cell compatibility, excellent transparency, and high refractive indices.

Supporting information Table of contents Efficient bioproduction of 4ACA.

A new synthetic route for high-performance biopolyamides with a rigid N-substituted pyrrolidone ring was developed from the biomonomer itaconic acid (IA), which was mass-produced by the fermentation of Aspergillus terreus. We used salt-type monomers composed of diacidic IA and diamines. These salts thermally converted into polyamides in the presence of sodium dihydrogen phosphate through the aza-Michael addition, followed by intramolecular cyclization to create a pyrrolidone ring in the polymer main chain. Polyamides with molecular weights ranging over 28 000 showed T g values over 87 °C, which were higher than conventional polyamides (around 57 °C). The Young's modulus and mechanical strength of these polyamides also showed high values of 430−2800 MPa and 90−165 MPa, respectively. In addition, the polyamides became soluble in water by ring-opening reaction of the pyrrolidone, which led to environmental corrosion by landfill or ultraviolet irradiation.

Aromatic polymers include novel and extant functional materials although none has been produced from biotic building blocks derived from primary biomass glucose. Here we screened microbial aromatic metabolites, engineered bacterial metabolism and fermented the aromatic lactic acid derivative β-phenyllactic acid (PhLA). We expressed the Wickerhamia fluorescens gene (pprA) encoding a phenylpyruvate reductase in Escherichia coli strains producing high levels of phenylalanine, and fermented optically pure (>99.9 %) D-PhLA. Replacing pprA with bacterial ldhA encoding lactate dehydrogenase generated L-PhLA, indicating that the produced enzymes converted phenylpyruvate, which is an intermediate of phenylalanine synthesis, to these chiral PhLAs. Glucose was converted under optimized fermentation conditions to yield 29 g/l D-PhLA, which was purified from fermentation broth. The product satisfied the laboratory-scale chemical synthesis of poly(D-PhLA) with M w 28,000 and allowed initial physiochemical characterization. Poly(D-PhLA) absorbed near ultraviolet light, and has the same potential as all other biomass-derived aromatic bioplastics of phenylated derivatives of poly(lactic acid). This approach to screening and fermenting aromatic monomers from glucose exploits a new era of bio-based aromatic polymer design and will contribute to petroleum conservation and carbon dioxide fixation.

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