An ionic liquid tolerant cellulase derived from chemically polluted microhabitats and its application in in situ saccharification of rice straw

• Characterized an ILs-tolerance cellulase from chemically polluted microhabitats.
• Some ILs activate the cellulase at a high concentration of 30% (v/v).
• Longer half-life of the cellulase in the presence of ILs than in buffer.
• Remarkable salt-stability of the cellulase.
• Developed an IL-cellulase system for the in situ saccharification of rice straw.

A cellulase-producing fungus was isolated from chemically polluted microhabitats by [Amim][Cl] enrichment and identified as Aspergillus fumigatus. The maximum activity of the cellulase in 30% (v/v) ionic liquids (ILs) was detected in [Emim][DMP], [Amim][Cl] and [Emim][MA] as 127%, 111% and 109%, respectively, of its activity in buffer, suggesting its superior performance in high concentration ILs. Strikingly, although its initial activity varied in each IL, its half-life was longer in most ILs than in buffer, evidence of a high conformational stability of the enzyme that is essential for maintaining the remaining activity in relevant media. It noteworthy that 1–3 M NaCl can activate the cellulase somewhat. More gratifyingly, a compatible IL-cellulase system based on the cellulase was developed, and its use significantly improved the saccharification rate of rice straw from 53% to 88% versus the control, demonstrating its potential for efficient transformation of lignocellulose to glucose in a single-step process.