(628c) A Synthetic Biology Chassis for Lignin Valorization into Muconic Acid and Other Value-Added Chemicals

Lignin represents an untapped portion of biomass for the production of fuels and chemicals. In nature, many aerobic organisms degrade lignin-derived aromatics through conserved intermediates including protocatechuate and catechol. Employing this microbial approach offers a potential solution for the bioconversion of lignin into value-added chemicals for a future biorefinery. In this study, two hybrid biochemical routes combining chemical catalysis, lignin bioengineering, and metabolic pathway reconstruction were demonstrated for the conversion of lignin into value-added products. In the biochemical route 1, alkali lignin was chemically catalyzed for the release of vanillin and syringate as major products, which were further bio-converted into cis, cis-muconic acid and pyrogallol through engineered E. coli strains. The highest yields achieved were at 0.63 g ccMA/g vanillin in the fermentation broth and 0.69 g ccMA/g vanillin in whole cells mixture. While the highest yield of pyrogallol in the fermentation broth was 7.3 mg pyrogallol/g syringate. In the second biochemical route, the lignin biosynthesis pathway of plant Arabidopsis was engineered to accumulate protocatechuate (PCA) as an intermediate compound. The PCA extracted from the engineered Arabidopsis was further converted into ccMA using the engineered E. coli strains. In this biochemical route, the extraction yield of PCA was 1.45 mg PCA/ g plant biomass. The highest yield of ccMA was achieved at 0.31 g ccMA/ g PCA or 0.45 mg ccMA/ g plant biomass. In addition to ccMA, catechol was produced at a higher yield of up to 0.54 g catechol/ g PCA or 0.79 mg catechol/ g plant biomass. This study reports for the first time a direct process for converting lignin into ccMA and pyrogallol as value-added chemicals. It provides a great alternative pathway for the production of fuels and valuable from lignin.