必須アミノ酸を生産する新しいカーボン・マイナス法(A New Carbon-Negative Method to Produce Essential Amino Acids)

2024-11-21 ジョージア工科大学

<関連情報>

• https://research.gatech.edu/new-carbon-negative-method-produce-essential-amino-acids
• https://pubs.acs.org/doi/10.1021/acssynbio.4c00359

無細胞生物触媒を用いたアミノ酸のカーボン・マイナス合成 Carbon Negative Synthesis of Amino Acids Using a Cell-Free-Based Biocatalyst

Shaafique Chowdhury,Ray Westenberg,Kimberly Wennerholm,Ryan A.L. Cardiff,Alexander S. Beliaev,Vincent Noireaux,James M. Carothers,and Pamela Peralta-Yahya
ACS Synthetic Biology  Published: November 21, 2024
DOI:https://doi.org/10.1021/acssynbio.4c00359

Abstract

Biological systems can directly upgrade carbon dioxide (CO₂) into chemicals. The CO₂ fixation rate of autotrophic organisms, however, is too slow for industrial utility, and the breadth of engineered metabolic pathways for the synthesis of value-added chemicals is too limited. Biotechnology workhorse organisms with extensively engineered metabolic pathways have recently been engineered for CO₂ fixation. Yet, their low carbon fixation rate, compounded by the fact that living organisms split their carbon between cell growth and chemical synthesis, has led to only cell growth with no chemical synthesis achieved to date. Here, we engineer a lysate-based cell-free expression (CFE)-based multienzyme biocatalyst for the carbon negative synthesis of the industrially relevant amino acids glycine and serine from CO₂ equivalents─formate and bicarbonate─and ammonia. The formate-to-serine biocatalyst leverages tetrahydrofolate (THF)-dependent formate fixation, reductive glycine synthesis, serine synthesis, and phosphite dehydrogenase-dependent NAD(P)H regeneration to convert 30% of formate into serine and glycine, surpassing the previous 22% conversion using a purified enzyme system. We find that (1) the CFE-based biocatalyst is active even after 200-fold dilution, enabling higher substrate loading and product synthesis without incurring additional cell lysate cost, (2) NAD(P)H regeneration is pivotal to driving forward reactions close to thermodynamic equilibrium, (3) balancing the ratio of the formate-to-serine pathway genes added to the CFE is key to improving amino acid synthesis, and (4) efficient THF recycling enables lowering the loading of this cofactor, reducing the cost of the CFE-based biocatalyst. To our knowledge, this is the first synthesis of amino acids that can capture CO₂ equivalents for the carbon negative synthesis of amino acids using a CFE-based biocatalyst. Looking ahead, the CFE-based biocatalyst process could be extended beyond serine to pyruvate, a key intermediate, to access a variety of chemicals from aromatics and terpenes to alcohols and polymers.