Kani Zilbeyaz

Asymmetric reduction of substituted acetophenones using once immobilized Rhodotorula glutinis cells

The asymmetric reductions of acetophenone and its analogues using once immobilized Rhodotorula glutinis cells were studied. The performance and reaction parameters of the immobilized cells were also investigated and it was determined that the cells could be used 15 times in batch processes. All chiral alcohols obtained using purification procedures were of sufficient enantiopurity (>99%) of the (S)-enantiomer. The applicability of the optimized process for a preparative scale bioreduction was shown. Under the optimum conditions, 35mM (4.3g) of the product ((S)-1-phenylethanol) was produced from 45mM (5.4g) of the substrate (acetophenone) with one time immobilized R. glutinis EBK-2 cells (6g wet weight). The yield was calculated as 77%. In this study, it was found that the buffer level had a very significant effect on the reaction activity. Our results demonstrate that the optimized process can be implemented on a preparative scale.

Highly enantiomeric reduction of acetophenone and its derivatives by locally isolated Rhodotorula glutinis.

Ninety isolates of microorganisms belonging to different taxonomical groups (30 bacteria, 20 yeast, and 40 fungi) were previously isolated from various samples. These isolates were screened as reducing agents for acetophenone 1a to phenylethanol 2a. It was found that the isolate EBK-10 was the most effective biocatalyst for the enantioselective bioreduction of acetophenone. This isolate was identified as Rhodotorula glutinis by the VITEK 2 Compact system. The various parameters (pH 6.5, temperature 32 degrees C, and agitation 200 rpm) of the bioreduction reaction was optimized, which resulted in conversions up to 100% with >99% enantiomeric excesses (ee) of the S-configuration. The preparative scale bioreduction of acetophenone 1a by R. glutinis EBK-10 gave (S)-1-phenylethanol 2a in 79% yield, complete conversion, and >99% ee. In addition, R.glutinis EBK-10 successfully reduced various substituted acetophenones.

Production of (R)-1-phenylethanols through bioreduction of acetophenones by a new fungus isolate Trichothecium roseum.

A total of 120 fungal strains were isolated from soil samples and evaluated in the bioreduction of substituted acetophenones to the corresponding (R)-alcohols. Among these strains, isolate Trichothecium roseum EBK-18 was highly effective in the production of (R)-alcohols with excellent enantioselectivity (ee > 99%). Gram scale preparation of (R)-1-phenylethanol is reported.

Efficient Synthesis of （S）-1-（2-chlorophenyl）ethanol in the Submerged Culture of Alternaria alternata Isolate

Abstract (S)-1-(2-chlorophenyl)ethanol is a key intermediate of L-cloprenaline used for relieving asthma symptoms. The asymmetric reduction of 2-chloroacetophenone 1 to (S)-1-(2-chlorophenyl)ethanol 2 in the submerged culture of Alternaria alternata isolates was studied. A. alternata EBK-8 isolate was the most effective biocatalyst. The bioactivity of the fungus could be significantly improved by the optimization of culture conditions. Parameters such as pH, temperature, agitation, and incubation time considerably influenced the substrate conversion and the optical purity of the product. The reaction was carried out in a culture medium at a substrate concentration of 30 mmol/L and produced the desired product with high conversion (100%) and isolated yield (80%) with an excellent enantiomeric excess (ee) of >99%. Under the optimum conditions, after 54 h reaction time, 24 mmol/L 2 from 30 mmol/L 1 could be produced. As a result, the submerged fermentation of A. alternata EBK-8 was found to be suitable for the asymmetric reduction of 1 to 2.