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Toward Optimizing and Understanding Reversible Hyperpolarization of Lactate Esters Relayed from para-Hydrogen.

ABSTRACT: The SABRE-Relay hyperpolarization method is used to enhance the ¹H and ¹³C NMR signals of lactate esters, which find use in a wide range of medical, pharmaceutical, and food science applications. This is achieved by the indirect relay of magnetization from para-hydrogen, a spin isomer of dihydrogen, to OH-containing lactate esters via a SABRE-hyperpolarized NH intermediary. This delivers ¹H and ¹³C NMR signal enhancements as high as 245- and 985-fold, respectively, which makes the lactate esters far more detectable using NMR. DFT-calculated J-couplings and spin dynamics simulations indicate that, while polarization can be transferred from the lactate OH to other ¹H nuclei via the J-coupling network, incoherent mechanisms are needed to polarize the ¹³C nuclei at the 6.5 mT transfer field used. The resulting sensitivity boost is predicted to be of great benefit for the NMR detection and quantification of low concentrations (

SUBMITTER: Tickner BJ

PROVIDER: S-EPMC9340809 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Toward Optimizing and Understanding Reversible Hyperpolarization of Lactate Esters Relayed from para-Hydrogen.

Tickner Ben J BJ Svensson S Karl-Mikael SK Vaara Juha J Duckett Simon B SB

The journal of physical chemistry letters 20220721 29

The SABRE-Relay hyperpolarization method is used to enhance the 1H and 13C NMR signals of lactate esters, which find use in a wide range of medical, pharmaceutical, and food science applications. This is achieved by the indirect relay of magnetization from para-hydrogen, a spin isomer of dihydrogen, to OH-containing lactate esters via a SABRE-hyperpolarized NH intermediary. This delivers 1H and 13C NMR signal enhancements as high as 245- and 985 ...[more]

PMID: 35861312

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Project description:BackgroundGreen organic solvents such as lactate esters have broad industrial applications and favorable environmental profiles. Thus, manufacturing and use of these biodegradable solvents from renewable feedstocks help benefit the environment. However, to date, the direct microbial biosynthesis of lactate esters from fermentable sugars has not yet been demonstrated.ResultsIn this study, we present a microbial conversion platform for direct biosynthesis of lactate esters from fermentable sugars. First, we designed a pyruvate-to-lactate ester module, consisting of a lactate dehydrogenase (ldhA) to convert pyruvate to lactate, a propionate CoA-transferase (pct) to convert lactate to lactyl-CoA, and an alcohol acyltransferase (AAT) to condense lactyl-CoA and alcohol(s) to make lactate ester(s). By generating a library of five pyruvate-to-lactate ester modules with divergent AATs, we screened for the best module(s) capable of producing a wide range of linear, branched, and aromatic lactate esters with an external alcohol supply. By co-introducing a pyruvate-to-lactate ester module and an alcohol (i.e., ethanol, isobutanol) module into a modular Escherichia coli (chassis) cell, we demonstrated for the first time the microbial biosynthesis of ethyl and isobutyl lactate esters directly from glucose. In an attempt to enhance ethyl lactate production as a proof-of-study, we re-modularized the pathway into (1) the upstream module to generate the ethanol and lactate precursors and (2) the downstream module to generate lactyl-CoA and condense it with ethanol to produce the target ethyl lactate. By manipulating the metabolic fluxes of the upstream and downstream modules through plasmid copy numbers, promoters, ribosome binding sites, and environmental perturbation, we were able to probe and alleviate the metabolic bottlenecks by improving ethyl lactate production by 4.96-fold. We found that AAT is the most rate-limiting step in biosynthesis of lactate esters likely due to its low activity and specificity toward the non-natural substrate lactyl-CoA and alcohols.ConclusionsWe have successfully established the biosynthesis pathway of lactate esters from fermentable sugars and demonstrated for the first time the direct fermentative production of lactate esters from glucose using an E. coli modular cell. This study defines a cornerstone for the microbial production of lactate esters as green solvents from renewable resources with novel industrial applications.

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Toward Optimizing and Understanding Reversible Hyperpolarization of Lactate Esters Relayed from para-Hydrogen.

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Toward Optimizing and Understanding Reversible Hyperpolarization of Lactate Esters Relayed from <i>para</i>-Hydrogen.

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Toward Optimizing and Understanding Reversible Hyperpolarization of Lactate Esters Relayed from para-Hydrogen.

Publications

Toward Optimizing and Understanding Reversible Hyperpolarization of Lactate Esters Relayed from &lt;i&gt;para&lt;/i&gt;-Hydrogen.

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Toward Optimizing and Understanding Reversible Hyperpolarization of Lactate Esters Relayed from <i>para</i>-Hydrogen.