BACKGROUNDMicrofluidic biocatalysis has advantages in terms of heat transfer and mass transfer. However, mass transfer in microscale conditions is often limited by excessive enzyme agglomeration, resulting in reduced reactor performance. In the present study, to establish an efficient and inexpensive microreaction system for obtaining high-value fine chemicals, a novel combined use of continuous-flow microchannel reactor and ionic liquid cosolvent for efficient production of isoquercitrin from rutin catalysed by unpurified recombinant enzyme RhaB1 was successfully carried out. RESULTSThe unpurified RhaB1 was expressed by BL21-pET21a-rhaB1 and the amino acid sequence was confirmed by Maldi-TOF-TOF, which was directly applied in microchannel reactors with an increased activity of 37.7% compared with the purified RhaB1, with [Toma][Tf2N] used as a cosolvent to avoid enzymatic agglomeration. A yield of 99.34.3% was achieved in 10min using crude RhaB1 in microchannel reactors under optimum conditions, and circular dichroism spectroscopy confirmed that [Toma][Tf2N] had a positive effect on RhaB1 activity. Compared with a batch reactor, the reaction time was reduced by 98.3%, the K-m was decreased to 1/3 and productivity was improved 61.4 times. CONCLUSIONResults indicated that the developed cosolvent system in the microfluidic reactor could improve the solubility and liquidity of recombinant RhaB1. The protocol is promising for industrial applications due to higher productivity and lower costs. (c) 2018 Society of Chemical Industry