Biotransformation of 1- and 2-phenylethanol to products of high value via redox reactions

Abstract

The aim of this research was to conduct biotransformation of phenolic compounds, prochiral ketone acetophenone into optically pure (R)-and (S)-1-phenylethanol and 2-phenylethanol into tyrosol and hydroxytyrosol. For acetophenone reduction reaction, the biocatalysts of choice were cyanobacteria, phototrophic microorganisms with biocatalytic potential that have not yet been fully discovered. For the hydroxylation reaction of 2-phenylethanol, instead of using vital Aspergillus niger cells, the reaction was carried out using the spores. As a result, high conversion rates were obtained (79.6%) for the reduction reaction performed by photobiocatalyst Nodularia sphaerocarpa, although the enantioselectivity was moderate (enantiomeric excess, ee 48%). The reaction carried out by cyanobacterium Leptolyngbya foveolarum yielded 25.7%, but with high enantioselectivity of (S)-1-phenylethanol 95% ee was received. It has also been proven that the acetophenone reduction did not depend on the light regime. For aromatic ring hydroxylation, several modifications of the conditions of biooxidation were introduced to maximize the effectiveness; the addition of glucose into the reaction medium gave the best results. As a result, new methods of bioconversion of phenylethyl alcohol have been developed, leading to the formation of desired products: 1-phenylethanol, tyrosol, and hydroxytyrosol antioxidants, compounds of utilitarian meaning.

Half-Preparative Scale Synthesis of (S)-1-Phenylethane-1,2-Diol as a Result of 2-Phenylethanol Hydroxylation with Aspergillus niger (IAFB 2301) Assistance

“…Next, experiments with spore suspensions were conducted in biotransformation medium supplemented with different glucose solutions (4 or 13 mM) in combination with various substrate concentrations (Table 1). This approach led to the single product hydroxytyrosol, and the productivity of the conversion increased from 5.4 mg/L (0.7% efficiency) (water media) [58] to 28.4 mg/L (five days, 13 mM of glucose solution and 15 mg/50 mL of substrate solution, 2.5 mM, 7.4% efficiency) (Table 5). The addition of glucose accelerates the germination of spores and, as a consequence, initiates the bioconversion and improves its effectiveness [56,59,60] (Table 5).…”

A Glimpse into Future Research on Microalgae Diversity, Ecology and Biotechnology

“…Acetophenone is often used as a model substrate for screening in case of bioreduction and it can undergo enantioselective bioreduction to R-or S-phenyl ethanol (1, Scheme 2). Several methods have been developed using whole cells of heterotrophic microorganisms or plant tissues [166][167][168], but typically these processes require co-substrates to support coenzyme regeneration systems. The intracellular oxidoreductase that is responsible for the asymmetric acetophenone reduction reaction is not itself dependent on light but requires the presence of reduced NAD(P)H, which is one of the products of the light phase of photosynthesis (Scheme 2).…”

Versatile Applications of Cyanobacteria in Biotechnology

“…Acetophenone is often used as a model substrate for screening in case of bioreduction and it can undergo enantioselective bioreduction to Ror S-phenyl ethanol (1, Scheme 2). Several methods have been developed using whole cells of heterotrophic microorganisms or plant tissues [166][167][168], but typically these processes require co-substrates to support coenzyme regeneration systems. The intracellular oxidoreductase that is responsible for the asymmetric acetophenone reduction reaction is not itself dependent on light but requires the presence of reduced NAD(P)H, which is one of the products of the light phase of photosynthesis (Scheme 2).…”