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. 2018 May 15;115(20):5093-5098.
doi: 10.1073/pnas.1800272115. Epub 2018 Apr 30.

Catalytic amino acid production from biomass-derived intermediates

Weiping Deng  1   2 , Yunzhu Wang  1 , Sui Zhang  1 , Krishna M Gupta  1 , Max J Hülsey  1 , Hiroyuki Asakura  3   4 , Lingmei Liu  5 , Yu Han  5 , Eric M Karp  6 , Gregg T Beckham  6 , Paul J Dyson  7 , Jianwen Jiang  1 , Tsunehiro Tanaka  3   4 , Ye Wang  2 , Ning Yan  8
Affiliations

Catalytic amino acid production from biomass-derived intermediates

Weiping Deng et al. Proc Natl Acad Sci U S A. .

Abstract

Amino acids are the building blocks for protein biosynthesis and find use in myriad industrial applications including in food for humans, in animal feed, and as precursors for bio-based plastics, among others. However, the development of efficient chemical methods to convert abundant and renewable feedstocks into amino acids has been largely unsuccessful to date. To that end, here we report a heterogeneous catalyst that directly transforms lignocellulosic biomass-derived α-hydroxyl acids into α-amino acids, including alanine, leucine, valine, aspartic acid, and phenylalanine in high yields. The reaction follows a dehydrogenation-reductive amination pathway, with dehydrogenation as the rate-determining step. Ruthenium nanoparticles supported on carbon nanotubes (Ru/CNT) exhibit exceptional efficiency compared with catalysts based on other metals, due to the unique, reversible enhancement effect of NH3 on Ru in dehydrogenation. Based on the catalytic system, a two-step chemical process was designed to convert glucose into alanine in 43% yield, comparable with the well-established microbial cultivation process, and therefore, the present strategy enables a route for the production of amino acids from renewable feedstocks. Moreover, a conceptual process design employing membrane distillation to facilitate product purification is proposed and validated. Overall, this study offers a rapid and potentially more efficient chemical method to produce amino acids from woody biomass components.

Keywords: amination; amino acids; catalysis; ruthenium; α-hydroxyl acids.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Catalytic transformation of biomass-derived α-hydroxyl acids into amino acids.
Fig. 2.
Fig. 2.
Catalytic conversion of lactic acid to alanine in a batch reactor. (A) Alanine yield with different metal catalysts. (B) Alanine yield across Ru-based catalysts on different supports. Reaction conditions: 0.5 mmol lactic acid, metal/substrate molar ratio = 0.025, 2.5 mL NH3H2O (25 wt %), 1 MPa H2, 493 K, 2 h. Error bars indicate SDs.
Fig. 3.
Fig. 3.
(A) Two possible reaction pathways for amination of lactic acid to alanine. (B) Dehydrogenation of isopropanol catalyzed by Pd/CNT and (C) Ru/CNT under a H2 atmosphere in a fixed-bed flow reactor. Green circles indicate isopropanol conversion, black triangles indicate acetone yield, and blue circles indicate isopropylamine yield. Reaction conditions: 50 mg catalyst, 2 μL/min isopropanol, 50 mL/min total flow rate, 473 K, 8 mL/min NH3 flow rate.
Fig. 4.
Fig. 4.
(A) Ru K-edge XANES spectra of various catalysts. (B) Fourier transformed Ru K-edge EXAFS spectra for fresh and spent Ru/CNT and Ru(OH)x/CNT catalysts. (C) XPS spectra of Ru 3p for fresh and spent Ru/CNT, Ru(OH)x/CNT catalysts. (D) H2-TPR profile of Ru/CNT and Ru(OH)x/CNT. STEM images of (E) fresh Ru/CNT and (F) spent Ru/CNT.
Fig. 5.
Fig. 5.
Ru/CNT recycling test for catalytic conversion of lactic acid to alanine. Reaction conditions: 0.5 mmol lactic acid, 50 mg Ru/CNT (Ru loading 3 wt %), 2.5 mL NH3H2O (25 wt %), 1 MPa H2, 493 K, 2 h. Turnover number of each catalytic cycle is calculated based on Ru dispersion of fresh Ru/CNT catalyst and the total Ru in the system.
Fig. 6.
Fig. 6.
A conceptual process diagram consists of a reactor, a membrane distillation unit, and two crystallizers.
See this image and copyright information in PMC

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