Use of deep eutectic solvents in microbial technology: A review.

Deep eutectic solvents (DESs) are new generation green solvents that fulfill most of the principles of green chemistry. A DES is a mixture formed by hydrogen bonds between two or more compounds, of which melting point is much lower than their constituents. They have unique properties such as high solvating capability, low vapor pressure, low toxicity, non-flammability, high thermal stability, easy preparation and being cost-effective. Furthermore, the properties of a DES can be designed for a specific application by proper combinations of their constituents; therefore, they are called "designer solvents" or "tailor-made" solvents. Deep eutectic solvents are successfully used in numerous fields including chemical reactions, biotransformations, bioactive compound extraction, gas absorption, nanoparticles synthesis, drug delivery, electrochemistry, electropolishing and electroanalysis, purification and production of biodiesel, and metal processing. Recently, with the increasing interest on green technologies, deep eutectic solvents have started to be used in applied microbiology. This review covers the applications of DESs in microbial technology as their utilization in fermentations and whole-cell biotransformations, extraction of bioproducts from the cells and cryopreservation of microorganisms.