Monitoring of enzymatic hydrolysis of ivory nut mannan using on-line microdialysis sampling and anion-exchange chromatography with integrated pulsed electrochemical detection

A new system for on-line monitoring of a small-scale bioprocess is described, based on microdialysis sampling and anion-exchange chromatography with integrated pulsed electrochemical detection. The microdialysis probe equipped with a 16-mm polysulfone membrane was used as an in situ sampling unit, giving a clean dialysate with no further need for sample clean-up. The system was used to continuously monitor the hydrolysis of 0.25% ivory nut mannan using endo-1,4-β-man-nanase (mannan endo-1,4-β-mannosidase; EC 3.2.1.78) from Aspergillus niger. The oligosaccharides produced in the hydrolysis, 1,4-β-d-mannobiose, mannotriose, mannotetraose, and mannopentaose, were separated isocratically and detected electrochemically. On-line monitoring of the hydrolysis of mannan using the endo-mannanase from A. niger, in a 5-ml reaction vessel, was achieved using 50 mM NaOH as mobile phase for 32 h without sampling or detection problems.