Abstract of PhD Thesis

In situ Enzymatic Conversion of Biomass into Glucose in Biodegradable Enzyme Compatible Ionic Liquids

Dong Yang, Dublin City University, 2015

This project was focused on the wood swelling, dissolution and regeneration in ionic liquids (ILs) and cellulose digestibility after wood pretreatment in ILs. Various ILs and their mixtures were used to swell wood chips of accurately measured linear dimensions.

A series of novel chiral ionic liquids were designed and synthesized in order to measure their thermal stability, biodegradability and antimicrobial toxicity. Amino acids and natural alcohol derivatives were the raw materials for the green synthesis of ILs. Tetrabutyl ammonium, tetraethyl ammonium and tetrapropyl ammonium hydroxide solution, as well as tetramethyl ammonium pentahydrate, were the other readily available starting materials for the IL preparation. The synthesis of these ILs was carried out conveniently by a one pot procedure in air. The biodegradability of 24 chiral ILs were assessed by the Closed Bottle test (CBT). Antifungal activity of the chiral ILs were determined against twelve fungal strains, and antimicrobial toxicity was determined against eight bacterial strains. All chiral ILs were found to have low toxicity towards eight strains of bacteria and twelve strains of fungi, although no ILs passed the CBT. The effects of absolute and relative stereochemistry and cation structure on the toxicity and biodegradability also have been determined.

These ILs have also been investigated as solvents in wood expansion, dissolution and regeneration studies. Cellulose and lignocellulose dissolution studies with ILs have shown the IL cation plays a significant role. In addition, the change in the swelling of the wood chips in ILs was correlated to cellulase digestibility results.