Method for producing refolded protein by using flow microreactor, and protein refolding apparatus

A protein refolding apparatus, comprising:

• a first flow path through which a buffer circulates;
• a second flow path through which a solubilized solution of a protein which has become insoluble or lost a higher-order structure thereof circulates;
• and
• a V-shaped micromixer having an inner diameter Y of 0.25 to 1.0 mm in which the first flow path and the second flow path are combined and mixed,
• wherein the micromixer is configured for bringing buffer having a flow rate of X1 mL/min into contact with the solubilized solution having a flow rate of X2 mL/min,
• a relationship between X1 and Y is shown by the following formula (1), and
• a relationship between X1 and X2 is shown by the following formula (2):
• Y≤ 1/180X1+⅘ (1)
• where 20≤X1≤300, and
• X2≤ 1/10X0 (2), and
• wherein the micromixer is configured for providing a mixing time of from 10 microseconds to 1,000 microseconds.