CHAPTER 9. Biomass-derived Solvents

The replacement of petroleum-derived solvents by more sustainable alternatives is one of the major concerns of Green Chemistry; under this philosophy, there is a growing interest in the development of “green solvents”, a category into which we can include a great variety of chemical structures, biomass-derived solvents (usually abbreviated as “biosolvents”) being one of the most promising options. These solvents share some similar properties with those derived from fossil resources, but at the same time satisfy several criteria (accessibility, biodegradability, little toxicity and affordable prices) required for being considered a more sustainable solution. In this chapter, we will comment on some well-known cases and present some recent examples aiming to exemplify the growing use of some of these biosolvents both for classical organic chemistry processes and in biotransformations mediated by biocatalysts, either isolated enzymes or whole cells. We have chosen 2-methyltetrahydrofuran (2-MeTHF, undeniably the most frequently employed), gamma-valerolactone (GVL), dihydrolevoglucosenone (Cyrene™) and glycerol-based solvents (GBSs), as these four paradigmatic biosolvents are probably those showing higher capability for being increasingly implemented in the next few years, not only in the lab but also at industrial scale. Thus, in this chapter, we will present some examples aiming to exemplify this attractive synergy; among the different reported cased, we will mainly focus on the use of biotransformations in 2-methyltetrahydrofuran (2-MeTHF, unquestionably the most frequently employed), gamma-valerolactone (GVL), dihydrolevoglucosenone (CyreneTM) and glycerol-based solvents (GBSs), stressing the inherent advantages of implementing the biocatalysts-biosolvent “green couple” on organic reactions not only at the lab but also at the industrial scale.