Sandy Schmidt
University of Greifswald
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Publication
Featured researches published by Sandy Schmidt.
Angewandte Chemie | 2015
Sandy Schmidt; Christian Scherkus; Jan Muschiol; Ulf Menyes; Till Winkler; Werner Hummel; Harald Gröger; Andreas Liese; Hans‐Georg Herz; Uwe T. Bornscheuer
Poly-ε-caprolactone (PCL) is chemically produced on an industrial scale in spite of the need for hazardous peracetic acid as an oxidation reagent. Although Baeyer-Villiger monooxygenases (BVMO) in principle enable the enzymatic synthesis of ε-caprolactone (ε-CL) directly from cyclohexanone with molecular oxygen, current systems suffer from low productivity and are subject to substrate and product inhibition. The major limitations for such a biocatalytic route to produce this bulk chemical were overcome by combining an alcohol dehydrogenase with a BVMO to enable the efficient oxidation of cyclohexanol to ε-CL. Key to success was a subsequent direct ring-opening oligomerization of in situ formed ε-CL in the aqueous phase by using lipase A from Candida antarctica, thus efficiently solving the product inhibition problem and leading to the formation of oligo-ε-CL at more than 20 g L(-1) when starting from 200 mM cyclohexanol. This oligomer is easily chemically polymerized to PCL.
Biotechnology and Bioengineering | 2016
Mark Dörr; Michael P. C. Fibinger; Sandy Schmidt; Javier Santos-Aberturas; Dominique Böttcher; Anke Hummel; Clare Vickers; Moritz Voss; Uwe T. Bornscheuer
A fully automatized robotic platform has been established to facilitate high‐throughput screening for protein engineering purposes. This platform enables proper monitoring and control of growth conditions in the microtiter plate format to ensure precise enzyme production for the interrogation of enzyme mutant libraries, protein stability tests and multiple assay screenings. The performance of this system has been exemplified for four enzyme classes important for biocatalysis such as Baeyer–Villiger monooxygenase, transaminase, dehalogenase and acylase in the high‐throughput screening of various mutant libraries. This allowed the identification of novel enzyme variants in a sophisticated and highly reliable manner. Furthermore, the detailed optimization protocols should enable other researchers to adapt and improve their methods. Biotechnol. Bioeng. 2016;113: 1421–1432.
Journal of Biotechnology | 2015
Sandy Schmidt; Maika Genz; Kathleen Balke; Uwe T. Bornscheuer
Baeyer-Villiger monooxygenases (BVMO) belong to the class B of flavin-dependent monooxygenases (type I BVMOs) and catalyze the oxidation of (cyclic) ketones into esters and lactones. The prototype BVMO is the cyclohexanone monooxygenase (CHMO) from Acinetobacter sp. NCIMB 9871. This enzyme shows an impressive substrate scope with a high chemo-, regio- and/or enantioselectivity. BVMO reactions are often difficult, if not impossible to achieve by chemical approaches and this makes these enzymes thus highly desired candidates for industrial applications. Unfortunately, the industrial use is hampered by several factors related to the lack of stability of these biocatalysts. Thus, the aim of this study was to improve the CHMOs long-term stability, one of the most relevant parameter for biocatalytic processes, and additionally its stability against oxidation. We used an easy computational method for the prediction of stabilizing disulfide bonds in the CHMO-scaffold. The three most promising predicted disulfide pairs were created and biochemically characterized. The most oxidatively stable variant (Y411C-A463C) retained nearly 60% activity after incubation with 25 mM H2O2 whereas the wild type retained only 16%. In addition, one extra disulfide pair (T415C-A463C) was created and tested for increased stability. The melting temperature (Tm) of this variant was increased by 5°C with simultaneous improved long-term stability. After verification by ABD-F labeling that this mutant does not form a disulfide bond, single and double Cys/Ser mutants were prepared and investigated. Subsequent analysis revealed that the T415C single point variant is the most stable variant with a 30-fold increased long-term stability (33% residual activity after 24h incubation at 25°C) showcasing a great achievement for practical applications.
Chemistry: A European Journal | 2018
Sandy Schmidt; Kathrin Castiglione; Robert Kourist
Multi-catalytic cascade reactions bear a great potential to minimize downstream and purification steps, leading to a drastic reduction of the produced waste. In many examples, the compatibility of chemo- and biocatalytic steps could be easily achieved. Problems associated with the incompatibility of the catalysts and their reactions, however, are very frequent. Cascade-like reactions can hardly occur in this way. One possible solution to combine, in principle, incompatible chemo- and biocatalytic reactions is the defined control of the microenvironment by compartmentalization or scaffolding. Current methods for the control of the microenvironment of biocatalysts go far beyond classical enzyme immobilization and are thus believed to be very promising tools to overcome incompatibility issues and to facilitate the synthetic application of cascade reactions. In this Minireview, we will summarize recent synthetic examples of (chemo)enzymatic cascade reactions and outline promising methods for their spatial control either by using bio-derived or synthetic systems.
Chemcatchem | 2016
Maika Genz; Okke Melse; Sandy Schmidt; Clare Vickers; Mark Dörr; Tom van den Bergh; Henk-Jan Joosten; Uwe T. Bornscheuer
Chiral amines are important building blocks, especially for the pharmaceutical industry. Although amine transaminases (ATAs) are versatile enzymes to synthesize chiral amines, the wildtype enzymes do not accept ketones with two large substituents next to the carbonyl functionality. Using bioinformatic tools to design a seven‐site mutant library followed by high‐throughput screening, we were able to identify variants of the enzyme from Vibrio fluvialis (VF‐ATA) with a widened binding pocket, as exemplified for a range of ketones. Three variants allowed the asymmetric synthesis of 2,2‐dimethyl‐1‐phenylpropan‐1‐amine—not accessible by any wildtype ATA described so far. The best variant containing four mutations (L56V, W57C, F85V, V153A) gave 100 % conversion of the ketone to yield the amine with an enantiomeric excess value >99 %, notably with preference for the (R)‐enantiomer. In silico modeling enabled the reconstruction of the substrate binding mode to the newly evolved pocket and, hence, allowed explanation of the experimental results.
Chemcatchem | 2015
Sandy Schmidt; Hanna C. Büchsenschütz; Christian Scherkus; Andreas Liese; Harald Gröger; Uwe T. Bornscheuer
Chiral polyesters in general can be employed for versatile biomedical purposes, but in vitro enzyme catalyzed biocatalytic routes by a multiple‐step cascade to make these functional biodegradable chiral polyesters have been hardly investigated. Recently, we developed an artificial three‐step enzymatic cascade synthesis by combining an alcohol dehydrogenase (ADH), a Baeyer–Villiger monooxygenase (BVMO) and a lipase (CAL‐A). Here, we extended this cascade for the synthesis of chiral methyl‐substituted oligo‐ɛ‐caprolactone derivatives to achieve both, the generation of chirality in a monomer and the subsequent polymerization. Several substrates were examined and provided access to functionalized chiral compounds in high yields (up to >99 %) and optical purities (up to >99 % ee). By subsequent enzymatic enantioselective ring opening of the enantiopure monomers, oligomeric lactones were successfully synthesized.
Biotechnology and Bioengineering | 2017
Christian Scherkus; Sandy Schmidt; Uwe T. Bornscheuer; Harald Gröger; Selin Kara; Andreas Liese
A computational approach for the simulation and prediction of a linear three‐step enzymatic cascade for the synthesis of ϵ‐caprolactone (ECL) coupling an alcohol dehydrogenase (ADH), a cyclohexanone monooxygenase (CHMO), and a lipase for the subsequent hydrolysis of ECL to 6‐hydroxyhexanoic acid (6‐HHA). A kinetic model was developed with an accuracy of prediction for a fed‐batch mode of 37% for substrate cyclohexanol (CHL), 90% for ECL, and >99% for the final product 6‐HHA. Due to a severe inhibition of the CHMO by CHL, a batch synthesis was shown to be less efficient than a fed‐batch approach. In the fed‐batch synthesis, full conversion of 100 mM CHL was 28% faster with an analytical yield of 98% compared to 49% in case of the batch synthesis. The lipase‐catalyzed hydrolysis of ECL to 6‐HHA circumvents the inhibition of the CHMO by ECL enabling a 24% higher product concentration of 6‐HHA compared to ECL in case of the fed‐batch synthesis without lipase. Biotechnol. Bioeng. 2017;114: 1215–1221.
Chemcatchem | 2016
Christian Scherkus; Sandy Schmidt; Uwe T. Bornscheuer; Harald Gröger; Selin Kara; Andreas Liese
A three‐step enzymatic reaction sequence for the synthesis of poly‐ϵ‐caprolactone (PCL) was designed running in a fed‐batch operation. The first part of the cascade consisted of two oxidation steps starting with alcohol dehydrogenase catalyzed oxidation from cyclohexanol to cyclohexanone and further oxidation to ϵ‐caprolactone (ECL) by means of a Baeyer–Villiger monooxygenase. As a third step, lipase‐catalyzed hydrolysis of the lactone to 6‐hydroxyhexanoic acid (6‐HHA) was designed. With this biocatalytic multistep process reported herein, severe substrate surplus and product inhibition could be circumvented by the fed‐batch operation by adding the cyclohexanol substrate and by in situ product removal of ECL by hydrolysis, respectively. Up to 283 mm product concentration of 6‐HHA was reached in the fed‐batch operated process without loss in productivity within 20 h. After extraction and subsequent polymerization catalyzed by Candida antarctica lipase B, analysis of the unfractionated polymer revealed a bimodal distribution of the polymer population, which reached a mass average molar mass (Mw) value of approximately 63 000 g mol−1 and a dispersity (Mw/Mn) of 1.1 for the higher molecular weight population, which thus revealed an alternative route to the conventional synthesis of PCL.
ChemBioChem | 2016
Andy Beier; Sven Bordewick; Maika Genz; Sandy Schmidt; Tom van den Bergh; Christin Peters; Henk-Jan Joosten; Uwe T. Bornscheuer
Baeyer–Villiger monooxygenases (BVMOs) catalyze the oxidation of ketones to esters or lactones by using molecular oxygen and a cofactor. Type I BVMOs display a strong preference for NADPH. However, for industrial purposes NADH is the preferred cofactor, as it is ten times cheaper and more stable. Thus, we created a variant of the cyclohexanone monooxygenase from Acinetobacter sp. NCIMB 9871 (CHMOAcineto); this used NADH 4200‐fold better than NADPH. By combining structure analysis, sequence alignment, and literature data, 21 residues in proximity of the cofactor were identified and targeted for mutagenesis. Two combinatorial variants bearing three or four mutations showed higher conversions of cyclohexanone with NADH (79 %) compared to NADPH (58 %) as well as specificity. The structural reasons for this switch in cofactor specificity of a type I BVMO are especially a hydrogen‐bond network coordinating the two hydroxy groups of NADH through direct interactions and bridging water molecules.
Green Chemistry | 2017
Sandy Schmidt; Tiago Pedroso de Almeida; Dörte Rother; Frank Hollmann
The one-pot multistep enzymatic oxidation of aliphatic and benzylic alcohols to the corresponding aldehydes combined with their subsequent carboligation to chiral α-hydroxy ketones has been exemplarily evaluated in terms of being a “green” biocatalytic approach. Besides the potential to start from bio-derived alcohols, this concept avoids the direct use of the reactive aldehyde intermediates, enables addition of high substrate concentrations in one liquid phase while maintaining enzyme activity and enables a simplified product isolation with diminished waste formation.