Renewable biodiesel is a widely accepted energy for its alternative use of petroleum diesel. Glycerol is an inevitable byproduct of biodiesel production. With the vigorous development of biodiesel industry, there is an obvious oversupply of glycerol. This over-generated green resource urgently needs further exploration for the sustainable new applications, which is critical to the development of biodiesel industry and is in accordance with the demands of green chemistry. In recent years, glycerol has become one of the most important raw material for the production of high value-added chemicals. Moreover, based on its special physicochemical properties, as well as degradability and good biocompatibility, glycerol plays an increasingly important role in biocatalysis and can be used as a new green solvent. This paper mainly reviews the progress on glycerol for industrial biotechnology application in microbial fermentation, biosynthesis and green solvent. Some practical application problems involved in glycerol biotransformation, such as feedstock quality and microbial utilization efficiency, are also discussed in detail. The future application development of glycerol in biocatalysis is also prospected.

Contents
1 Introduction
2 Glycerol uptake and intracellular metabolism
3 Glycerol for microbial growth
4 Glycerol-based raw material for biotransformation
4.1 Glycerol to value-added chemicals
4.2 Solution to the inhibition of high glycerol concentration
4.3 Strategy for biotransformation efficiency
4.4 Bioconversion of crude glycerol
5 Application of glycerol in biocatalysis
5.1 Biocompatibility of glycerol
5.2 Application in asymmetric bioreduction
5.3 Glycerol as green solvent
5.4 Glycerol to deep eutectic solvents (DESs)
6 Conclusion