Effects of caffeine on stereoselectivities of high cell density biotransformations of cyclic β-keto esters with Saccharomyces cerevisiae

Bohn, Mathilde; Leppchen, Kathrin; Katzberg, Michael; Lang, Alexander; Steingroewer, Juliane; Weber, Jost; Bley, Thomas; Bertau, Martin

doi:10.1039/b709716f

Cited by 11 publications

(4 citation statements)

References 52 publications

(15 reference statements)

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“…Different kinds of biological reducing agents such as sp. AS2.2241, 157 plant tissues, 158 coconut water (Cocos nucifera L.), 159,160 grapes, 161,162 red algae (Cyanidioschyzon merolae 10D and Cyanidium caldarium) 163 and soaked Phaseolus aureus 164 were used in the reduction of aromatic and aliphatic organic ketones and esters. It is expected that these kinds of reducing agents will be a good choice for the reduction of GO to graphene.…”

Section: Conclusion and Future Research Directionsmentioning

confidence: 99%

Recent advances in the efficient reduction of graphene oxide and its application as energy storage electrode materials

et al. 2013

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Efficient reduction of graphene oxide (GO) by chemical, thermal, electrochemical, and photo-irradiation techniques has been reviewed. Particular emphasis has been directed towards the proposed reduction mechanisms of GO by different reducing agents and techniques. The advantages of using different kinds of reducing agents on the basis of their availability, cost-effectiveness, toxicity, and easy product isolation processes have also been studied extensively. We provide a detailed description of the improvement in physiochemical properties of reduced GO (RGO) compared to pure GO. For example, the electrical conductivity and electrochemical performance of electrochemically obtained RGO are much better than those of chemically or thermally RGO materials. We provide examples of how RGO has been used as supercapacitor electrode materials. Specific capacitance of GO increases after reduction and the value has been reported to be 100-300 F g(-1). We conclude by proposing new environmentally friendly types of reducing agents that can efficiently remove oxygen functionalities from the surface of GO.

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Section: Conclusion and Future Research Directionsmentioning

confidence: 99%

Recent advances in the efficient reduction of graphene oxide and its application as energy storage electrode materials

et al. 2013

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“…29 But stress responses of whole-cells can also be used to control stereoselectivity of reductions of xenobiotics by adding a physiologically active substance. 30 Thus expression of reductases may be altered without the need for genetic modification. Hence the use of whole-cells of S. cerevisiae should not be ruled out a priori.…”

Section: The Whole-cell-biocatalyst Saccharomyces Cerevisiaementioning

confidence: 99%

Biocatalytical production of (5S)-hydroxy-2-hexanone

et al. 2009

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Biocatalytical approaches have been investigated in order to improve accessibility of the bifunctional chiral building block (5S)-hydroxy-2-hexanone ((S)-2). As a result, a new synthetic route starting from 2,5-hexanedione (1) was developed for (S)-2, which is produced with high enantioselectivity (ee >99%). Since (S)-2 can be reduced further to furnish (2S,5S)-hexanediol ((2S,5S)-3), chemoselectivity is a major issue. Among the tested biocatalysts the whole-cell system S. cerevisiae L13 surpasses the bacterial dehydrogenase ADH-T in terms of chemoselectivity. The use of whole-cells of S. cerevisiae L13 affords (S)-2 from prochiral 1 with 85% yield, which is 21% more than the value obtained with ADH-T. This is due to the different reaction rates of monoreduction (1-->2) and consecutive reduction (2-->3) of the respective biocatalysts. In order to optimise the performance of the whole-cell-bioreduction 1 2 with S. cerevisiae, the system was studied in detail, revealing interactions between cell-physiology and xenobiotic substrate and by-products, respectively. This study compares the whole-cell biocatalytic route with the enzymatic route to enantiopure (S)-2 and investigates factors determining performance and outcome of the bioreductions.

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“…However, in the last years a number of interesting studies has been published that show the usefulness of the technique for biotechnologists. Many applications can be found in the field of cell engineering: FCM and cell sorters are very handy tools, for example, for the identification of new strong promoters (Bi et al, 2002), to recognize stress caused by the reaction conditions (Bohn et al, 2007), for screening of strains tolerant to these stresses (like low pH values; Valli et al, 2006) and to monitor for stability of recombinant gene expression. Here FCM is very useful as due to its throughput and speed of analysis it allows detecting of rare events .…”

Section: Introductionmentioning

confidence: 99%

Asymmetric division of Hansenula polymorpha reflected by a drop of light scatter intensity measured in batch microtiter plate cultivations at phosphate limitation

Kottmeier

Weber

Müller

et al. 2009

Biotech & Bioengineering

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Hansenula polymorpha RB11 pC10-FMD (P(FMD)- GFP) (FMD promoter gfp gene) was simultaneously cultivated in the Respiration Activity Monitoring System (RAMOS) and in the microtiter plate cultivation system "BioLector" under phosphate limitation. The light scatter signal of the BioLector, for the determination of the biomass concentration in the wells, shows a significant decrease with the onset of the phosphate limitation until a stationary level is reached. At lower initial phosphate concentration this effect is more pronounced and longer time is required until the stationary level of the scattered light is achieved. The oxygen transfer rate signal of the RAMOS and the light scatter signal of the BioLector correlate with respect to the points of time where the maxima and the stationary levels of the courses are reached. In order to understand the effect causing this light scatter behavior, the forward and side scatter properties were investigated off line by flow cytometry. The decay in the light scatter of the BioLector seems to correlate with the formation of two subpopulations of different scatter intensities detected by a flow cytometer. With ongoing cultivation the fraction of cells possessing higher light scattering properties decreases until only a population of lower light scattering properties exists. The rate of transition of the yeast from one subpopulation to the other appears to be correlated with the rate of decrease in the BioLector light scatter signal. The formation of the subpopulations may be caused by an increased asymmetry in the cell cycle due to phosphate limitation.

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Effects of caffeine on stereoselectivities of high cell density biotransformations of cyclic β-keto esters with Saccharomyces cerevisiae

Cited by 11 publications

References 52 publications

Recent advances in the efficient reduction of graphene oxide and its application as energy storage electrode materials

Recent advances in the efficient reduction of graphene oxide and its application as energy storage electrode materials

Biocatalytical production of (5S)-hydroxy-2-hexanone

Asymmetric division of Hansenula polymorpha reflected by a drop of light scatter intensity measured in batch microtiter plate cultivations at phosphate limitation

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