Microbial monomers custom-synthesized to build true bio-derived aromatic polymers

Abstract

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.

Phenyllactic acid production by simultaneous saccharification and fermentation of pretreated sorghum bagasse

“…In lactic acid bacteria, PhLA is naturally produced from glucose by the non-specific reduction of phenylpyruvate (Mu et al, 2009). A recombinant Escherichia coli strain expressing the Wickerhamia fluorescens pprA gene, which encodes phenylpyruvate reductase, was also able to produce optically pure D-PhLA from glucose (Fujita et al, 2013). This finding suggests that D-PhLA can be produced from the enzymatic hydrolysate of cellulosic feedstocks.…”

“…One FPU was defined as the amount of enzyme that released 1 lmol of glucose equivalents from Whatman Qualitative Grade 1 Filter Paper per minute. Both enzymatic hydrolysis and microbial fermentation, including SHF and SSF, were conducted using fermentation medium (Fujita et al, 2013).…”

“…Unlike polylactic acid, poly-PhLA exhibits high ultraviolet-absorbing properties due to the bulky aromatic side chain (Fujita et al, 2013). In lactic acid bacteria, PhLA is naturally produced from glucose by the non-specific reduction of phenylpyruvate (Mu et al, 2009).…”

“…3-Phenyllactic acid (PhLA) is a promising building block for biobased materials, as PhLA can be polymerized into the biopolymer poly-PhLA (Fujita et al, 2013). Unlike polylactic acid, poly-PhLA exhibits high ultraviolet-absorbing properties due to the bulky aromatic side chain (Fujita et al, 2013).…”

Phenyllactic Acid: A Potential Antimicrobial Compound in Lactic acid Bacteria

“…PhLA and their derivatives also act as a chiral building block for the synthesis of many bio-based materials in agricultural, pharmaceutical and chemistry fields [12,13,14]. It can be polymerized in to poly-PhLA which unlike polylactic acid showed high ultraviolet absorption ability and thermostability due to bulky aromatic side chain [15,16]. The antimicrobial property, the promising applications of PhLA and its great demand sparked the great interest in the development of various strategies for its synthesis.…”