Influence of surfactants on microbial degradation of organic compounds

Abstract

Surfactants have the ability to increase aqueous concentrations of poorly soluble compounds and interfacial areas between immiscible fluids, thus potentially improving the accessibility of these substrates to microorganisms. However, both enhancements and inhibitions of biodegradation of organic compounds in the presence of surfactants have been reported. The mechanisms behind these phenomena are not well understood. To better understand the factors involved and the current state of knowledge in this field, a search of the literature concerning the influence of commercial surfactants and biosurfactants on microbial metabolism has been conducted. Factors pertaining to surfactant‐substrate interactions such as emulsification, solubilization, and partitioning of hydrocarbons between phases, all of which can influence accessibility of substrates to microorganisms, are of concern. Also, due to the direct interaction of surfactants with microorganisms, it appears that steric or conformational compatibility of surfactants with cell membrane lipids and enzymes is an important metabolic factor. Weaknesses in the general data base are evident, such as the lack of research involving Gram‐positive organisms and ionic surfactants. It is also worthy to note that research involving commercial surfactants and mixed microbial cultures has shown a correlation between inhibited biodegradation of hydrocarbons and surfactant concentrations above the critical micelle concentration. This is a significant point of interest when remedial efforts involving indigenous organisms in natural environments are being considered.

Key words:

• surfactant
• biosurfactant
• emulsifier
• solubilization
• emulsification
• biodegradation
• hydrocarbons