Abstract
Spent coffee grounds (SCGs) are a renewable source that can be converted into different types of biofuels or chemicals. Recent research has focused on the examination of a two-step bioconversion process that involves;1) extraction of fermentable sugars from SCGs, and 2) conversion of sugars into fuels and/or chemicals by microbial fermentation. The capability of SCGs as a source of fermentable sugars has not been fully realised, due to their complex structure. Which makes the depolymerisation of the SCGs into its component monomeric sugars relativity difficult. The use of ionic liquids (ILs) as green solvents is an attractive alternative for the pre-treatment of lignocellulosic biomass such as SCGs. It has been shown that pre-treatment with imidazolium-based ILs containing anions such as chloride, acetate, and alkyl phosphate can greatly speed up the subsequent enzymatic hydrolysis of lignocellulosic biomass. The present investigated the use of 1-Butyl-3- methylimidazolium chloride as a green solvent for the extraction of sugars from SCGs for the production of bioethanol. The maximum concentration of sugars extracted was 22.55 wt% of mannose in 100 g of SCGs, galactose, 15 wt% of galactose in 100 g of used, 9.81 wt% glucose in 100 g of SCGs, 6.36 wt% arabinose and 10.46 wt% of, sucrose in 100 g of dry SCGs used. Mannose yield was prominent in all runs, the high content of this sugar causes difficulty in bioethanol production but is advantageous in the production of itaconic acid.
