Transitioning from conventional batch to microfluidic processes for the efficient singlet oxygen photooxygenation of methionine

•The photooxygenation of (L)-methionine by 1O2 was studied in a batch reactor.•Optimization of photosensitizer concentration, light intensity and O2 was carried out.•The photooxygenation was next implemented under microfluidic conditions.•Both process technologies were assessed, emphasizing better performances for the microreactor.