Biosynthesis of Furfurylamine from Biomass-Derived Furfural Using Transaminase RTTA-LF with Moderate Inhibitor Tolerance

Lignocellulosic biomass, as the most abundant renewable carbon resource on earth, provides a sustainable feedstock for valuable chemicals. This study developed an integrated chemobiocatalytic cascade process for the direct conversion of lignocellulosic biomass to furfurylamine, an important pharmaceutical intermediate and fine chemical raw material. A biochar-based magnetic bifunctional solid acid catalyst (PMSA) was constructed and shown to efficiently catalyze biomass conversion to furfural. The magnetic separability and operational stability of PMSA were demonstrated using sorghum straw, affording a furfural yield of 73.6% and maintaining high catalytic efficiency over four consecutive reuse cycles. To address the equilibrium limitations and cofactor dependency in enzymatic transamination, a three-enzyme cascade system ( E. coli RTTA-LF) was constructed by co-expressing a transaminase from Ruegeria sp. TM1040 (RTTA) with lactate dehydrogenase (LpLDH) and formic acid dehydrogenase (FDH) in Escherichia coli and applied in a low-transition-temperature mixture (LTTM), TMBAC:Gly medium. This system ingeniously employs LpLDH to remove the inhibitory by-product pyruvate by reducing it to lactate, thereby driving the transamination equilibrium toward furfurylamine synthesis. Under the optimized conditions (30 °C, pH 7.0, l -alanine:furfural = 12:1, mol:mol), the whole-cell biocatalyst successfully converted various biomass-derived furfural (50 mM) into furfurylamine with a conversion of >95% within 6 h, while showing good tolerance toward typical inhibitors such as 5-hydroxymethylfurfural and levulinic acid. Finally, the integrated cascade was evaluated across diverse lignocellulosic biomass, among which corn stover emerged as the optimal substrate under the conditions (181 °C, 20 min), delivering 82.9 mM furfural (corresponding to 80.4% yield based on xylan content) and subsequently 158.4 mg furfurylamine per gram of corn stover. The strategy further demonstrated broad substrate universality, successfully converting beech wood, maple wood, poplar wood, yellow bamboo, bagasse, and sorghum straw into furfurylamine. In conclusion, this work provides a sustainable route for the production of furfurylamine and its derivatives from renewable biomass.