Susanna Bertuletti

Bio: Susanna Bertuletti is an academic researcher from University of Milan. The author has contributed to research in topics: Hydroxysteroid Dehydrogenases & Chemistry. The author has an hindex of 2, co-authored 4 publications receiving 13 citations.

Stereoselective Biocatalyzed Reductions of Ginger Active Components Recovered from Industrial Wastes

Abstract: Ginger is among the most widespread and widely consumed traditional medicinal plants around the world. Its beneficial effects, which comprise e. g. anticancer and anti‐inflammatory activities as well as gastrointestinal regulatory effects, are generally attributed to a family of non‐volatile compounds characterized by an arylalkyl long‐chained alcohol, diol, or ketone moiety. In this work, ginger active components have been successfully recovered from industrial waste biomass of fermented ginger. Moreover, their recovery has been combined with the first systematic study of the stereoselective reduction of gingerol‐like compounds by isolated alcohol dehydrogenases (ADHs), obtaining the enantioenriched sec‐alcohol derivatives via a sustainable biocatalytic path in up to >99 % conversions and >99 % enantiomeric/diastereomeric excesses.

Synthesis of ω-Muricholic Acid by One-Pot Enzymatic Mitsunobu Inversion using Hydroxysteroid Dehydrogenases

Abstract: The biocatalyzed conversion of hyocholic acid (3α,6α,7α‐trihydroxy‐5β‐cholan‐24‐oic acid) into ω‐muricholic acid (3α,6α,7β‐trihydroxy‐5β‐cholan‐24‐oic acid) has been obtained exploiting a small library of 7α‐ and 7β‐HSDHs (hydroxysteroid dehydrogenases). The process has been optimized and performed avoiding the isolation of the 7‐oxo intermediate using the appropriate coupled enzymes for the in situ cofactor regeneration. Moreover, the biocatalyzed reduction of 6,7‐dioxolithocholic acid (3α‐hydroxy‐6,7‐dioxo‐5β‐cholan‐24‐oic acid) was also investigated.

Biocatalytic axidation of alcohols

Abstract: Enzymatic methods for the oxidation of alcohols are critically reviewed. Dehydrogenases and oxidases are the most prominent biocatalysts, enabling the selective oxidation of primary alcohols into aldehydes or acids. In the case of secondary alcohols, region and/or enantioselective oxidation is possible. In this contribution, we outline the current state-of-the-art and discuss current limitations and promising solutions.

Taking Advantage of Promiscuity of Cold-Active Enzymes

Abstract: Cold-active enzymes increase their catalytic efficiency at low-temperature, introducing structural flexibility at or near the active sites. Inevitably, this feat seems to be accompanied by lower thermal stability. These characteristics have made cold-active enzymes into attractive targets for the industrial applications, since they could reduce the energy cost in the reaction, attenuate side-reactions, and simply be inactivated. In addition, the increased structural flexibility could result in broad substrate specificity for various non-native substrates, which is called substrate promiscuity. In this perspective, we deal with a less addressed aspect of cold-active enzymes, substrate promiscuity, which has enormous potential for semi-synthesis or enzymatic modification of fine chemicals and drugs. Further structural and directed-evolutional studies on substrate promiscuity of cold-active enzymes will provide a new workhorse in white biotechnology.

Alcohol Dehydrogenases as Catalysts in Organic Synthesis

Abstract: Alcohol dehydrogenases (ADHs) have become important catalysts for stereoselective oxidation and reduction reactions of alcohols, aldehydes and ketones. The aim of this contribution is to provide the reader with a timely update on the state-of-the-art of ADH-catalysis. Mechanistic basics are presented together with practical information about the use of ADHs. Current concepts of ADH engineering and ADH reactions are critically discussed. Finally, this contribution highlights some prominent examples and future-pointing concepts.

Generation of Oxidoreductases with Dual Alcohol Dehydrogenase and Amine Dehydrogenase Activity.

Abstract: The l-lysine-e-dehydrogenase (LysEDH) from Geobacillus stearothermophilus naturally catalyzes the oxidative deamination of the e-amino group of l-lysine. We previously engineered this enzyme to create amine dehydrogenase (AmDH) variants that possess a new hydrophobic cavity in their active site such that aromatic ketones can bind and be converted into α-chiral amines with excellent enantioselectivity. We also recently observed that LysEDH was capable of reducing aromatic aldehydes into primary alcohols. Herein, we harnessed the promiscuous alcohol dehydrogenase (ADH) activity of LysEDH to create new variants that exhibited enhanced catalytic activity for the reduction of substituted benzaldehydes and arylaliphatic aldehydes to primary alcohols. Notably, these novel engineered dehydrogenases also catalyzed the reductive amination of a variety of aldehydes and ketones with excellent enantioselectivity, thus exhibiting a dual AmDH/ADH activity. We envisioned that the catalytic bi-functionality of these enzymes could be applied for the direct conversion of alcohols into amines. As a proof-of-principle, we performed an unprecedented one-pot "hydrogen-borrowing" cascade to convert benzyl alcohol to benzylamine using a single enzyme. Conducting the same biocatalytic cascade in the presence of cofactor recycling enzymes (i.e., NADH-oxidase and formate dehydrogenase) increased the reaction yields. In summary, this work provides the first examples of enzymes showing "alcohol aminase" activity.