Nonionic Micelles Promote Whole Cell Bioconversion of Aromatic Substrates in an Aqueous Environment

Abstract

This paper illustrates the use of a nonionic micellar system to enhance the efficiency of a bacterial whole cell oxidation of a polycyclic aromatic substrate. We have studied the biotransformation of naphthalene operated by an isolated strain of an engineered Escherichia coli to (+)-cis-(1R,2S)-dihydroxy-1,2dihydronaphthalene in a direct micellar system and in microemulsion. The rationale of the use of an engineered bacterial strain is the high regiochemical and stereochemical specificity in yielding chiral precursors that can be subsequently used in a variety of syntheses of technological and pharmaceutical interest. These bacteria are able to degrade several polycyclic aromatic hydrocarbons (PAHs). Since these substrates are poorly water soluble, new reaction media have to be designed, where such microorganisms are still viable and fully efficient. In a narrow composition range of the L1 phase region, the ternary system Triton X100/water/ethyloleate provides an ideal microcompartmented medium, where the engineered bacteria grow and where the PAH solubility and bioavailability increase the efficiency of bacterial conversion. A physicochemical characterization of the micellar phase and the conversion efficiency has been studied as a function of the oil content.

Whole cell microbial transformation in cloud point system

“…Some nonionic surfactants micelle solution with a relatively lower surfactant concentration has been applied to enhance the bioavailability of hydrophobic compounds [46][47][48]. However, the permeability of a nonionic surfactant to microbial cells makes the nonionic surfactant toxic to the microorganism [49].…”

“…A very low nonionic surfactant micelle solution is biocompatible and has been applied in biotechnology [46][47][48]. Analogue to the log P is chosen as a parameter for an organic solvent, the cloud point of a nonionic surfactant may act as a criterion for a nonionic surfactant.…”