Cinnamic acid (CA) is the chemical basis for bulk production of flavoring
reagents and chemical intermediates, and it can be fermented from biomass.
Phenylalanine ammonia lyase (PAL) has been used exclusively in the bacterial fermentation of
sugar biomass in which the fermentation intermediate
phenylalanine is deaminated to CA. Here, we designed an alternative metabolic pathway for fermenting
glucose to CA. An Escherichia coli strain that generates
phenylalanine in this pathway also produces Wickerhamia fluorescens
phenylpyruvate reductase and ferments
glucose to D-phenyllactate (D-PhLA) (Fujita et al. Appl Microbiol Biotechnol 97: 8887-8894, 2013). Thereafter,
phenyllactate dehydratase encoded by fldABCI genes in Clostridium sporogenes converts the resulting D-PhLA into CA. The
phenyllactate dehydratase expressed by fldABCI in the D-PhLA-producing bacterium fermented
glucose to CA, but D-PhLA fermentation and phenyllactate
dehydration were aerobic and anaerobic processes, respectively, which disrupted high-yield CA fermentation in single batch cultures. We overcame this disruption by sequentially culturing the two strains under aerobic and anaerobic conditions. We optimized the incubation periods of the respective aeration steps to produce 1.7 g/L CA from
glucose, which exceeded the yield from PAL-dependent
glucose fermentation to CA 11-fold. This process is a novel, efficient alternative to conventional PAL-dependent CA production.