Assessing bioavailability of the solubilization of organic compound in nonionic surfactant micelles by dose-response analysis.

It is uncertain in some extent that organic compounds solubilized in micelles of a nonionic surfactant aqueous solution are bioavailable directly by the microbes in an extractive microbial transformation or biodegradation process. In this work, a dose-response method, where a bioequivalence concept is introduced to evaluate the synergic toxicity of the nonionic surfactants and the organic compounds, was applied to analyze the inhibition effect of organic compounds (naphthalene, phenyl ether, 2-phenylethanol, and 1-butanol) in nonionic surfactant Triton X-100 micelle aqueous solutions and Triton X-114 in aqueous solutions forming cloud point systems. Based on the result, a mole solubilization ratio of organic compounds in micelle was also determined, which consisted very well with those of classic semi-equilibrium dialysis experiments. The results exhibit that bioavailability of organic compounds solubilized in micelles to microbial cells is negligible, which provides a guideline for application of nonionic surfactant micelle aqueous solutions or cloud point systems as novel media for microbial transformations or biodegradations.

Extractive microbial fermentation in cloud point system.

Extractive microbial fermentation of organic compounds in liquid-liquid two-phase systems is a potential strategy to overcome the limitations of microbial fermentation in an aqueous solution, such as low substrate solubility, substrate/product inhibition and product further degradation. A conventional aqueous-organic solvent two-phase system is inaccessible to extractive fermentation of a relatively high polar bioproduct as the confliction between the biocompatibility and the extraction ability of the corresponding organic solvent. An exploitation of cloud point system as a novel medium engineering method for extractive microbial fermentation is reviewed in present work. The relationship between phase separation of nonionic surfactant aqueous solution forming cloud point system and its corresponding biocompatibility to microorganisms, and the relationship between solubilization and bioavailability of organic compounds in a cloud point system are discussed. Paradigms of extractive microbial fermentation in cloud point system are highlighted with some cases in our lab. The downstream processing for nonionic surfactant recovery and product separation with microemulsion extraction is also presented.