Application of cyanobacteria for chiral phosphonate synthesis

Abstract

This is the first report on morphologically different strains of cyanobacteria: Arthrospira maxima, Nostoc cf-muscorum and Nodularia sphaerocarpa used for enantioselective bioreduction of selected, structurally different diethyl esters of oxophosphonic acids. The efficiency of the asymmetric hydrogen transfer was strongly dependent on the chemical structure of the substrates. Arthrospira maxima was active only toward diethyl (S)-2-oxopropylphosphonate (20% of yield, 99% of ee), whereas the application of Nostoc cf-muscorum as a biocatalyst allowed diethyl (S)-2-hydroxy-2-phenylethylphosphonate with a high enantiomeric excess (99%) and with 26% conversion degree to be obtained. Employing Nodularia sphaerocarpa led to the most spectacular result -diethyl (S)-2-hydroxy-2-phenylethylphosphonate with a degree of conversion of 99% and an optical purity of 92%. Enantioselective bioconversion of oxophosphonate with an aromatic side group located in the immediate vicinity of the carbonyl functionality was achieved for the first time. Additionally, flow cytometry showed excellent resistance of the cells of Nodularia sphaerocarpa against the examined xenobiotic -2-oxo-2-phenylethylphosphonate, these cells remain viable at the concentration of 10 mM of the bioconversion substrate compared to the 1 mM described previously for a fungal biocatalyst. The effect of cultivation medium, light source and light cycle (light : dark) on the effectiveness of the biotransformation process was examined.

Enzymatic Oxyfunctionalization Driven by Photosynthetic Water-Splitting in the Cyanobacterium Synechocystis sp. PCC 6803

“…Using wildtype cells without the recombinant BVMO, we did not observe any measurable oxidation of any of the ketones. Ketoreduction by endogenous alcohol dehydrogenases [12], and the selective reduction of cinnamyl aldehyde in Synechocystis have been reported before [11]. Indeed, we also found that wildtype Synechocystis cells without the chmo gene catalysed the reduction in 1a and 1c-f to the corresponding alcohols.…”

“…In biotransformation reactions with a substrate concentration of 5 mM, the methyl-substituted ketones 1c-e were converted with a specific activity between 2 to 5 U/gCDW (Tables 1 and 2). This activity is a result of the Baeyer-Villiger oxidation and the competing Ketoreduction by endogenous alcohol dehydrogenases [12], and the selective reduction of cinnamyl aldehyde in Synechocystis have been reported before [11]. Indeed, we also found that wildtype Synechocystis cells without the chmo gene catalysed the reduction in 1a and 1c-f to the corresponding alcohols.…”

“…It is known that Synechocystis harbours alcohol dehydrogenases that catalyse the reduction of ketones, which was recently exploited for the asymmetric synthesis of chiral phosphonates [12], and the selective reduction of cinnamyl aldehyde [11]. Hölsch et al demonstrated that an alcohol dehydrogenase from Synechococcus sp.…”

“…The feasibility to recycle NADPH via photosynthesis by Synechococcus elongatus PCC7942 has been shown with endogenous alcohol dehydrogenases acting on aryl-aliphatic ketones [9,10]. With other cyanobacterial strains, the feasibility to reduce aldehydes [11] and phosphonates [12] was also shown. We have recently shown that this approach can be also extended toward recombinant enzymes by introducing a bacterial ene-reductase into the cyanobacterium Synechocystis sp.…”

Reductive activity of free and immobilized cells of cyanobacteria toward oxophosphonates—comparative study

“…Enantioselectivity as well as cell viability remained almost at the same level (Górak and Żymańczyk-Duda 2015). Thus, current efforts involve an increase in both values and were also focused on creating the economic system that allows reuse of biocatalyst.…”