ON-LINE QUANTITATION OF ENZYMATIC MANNAN HYDROLYSATES IN SMALL-VOLUME BIOREACTORS BY MICRODIALYSIS SAMPLING AND COLUMN LIQUID CHROMATOGRAPHY-INTEGRATED PULSED ELECTROCHEMICAL DETECTION

摘要

Quantitative aspects of on-line microdialysis sampling are investigated with respect to sampling in small-volume bioreactors. Three modes of microdialysis sampling; continuous-flow microdialysis sampling (CFMS), stopped-flow microdialysis sampling with continuous stirring, and stopped-how microdialysis sampling with stopped stirring were investigated as a possible means for studying bioprocesses. The hydrolytic properties of a well characterised endomannanase from Aspergillus niger were studied using 0.01% ivory nut mannan as substrate in a 5-ml reaction vessel. On-line sampling was achieved using a microdialysis probe fitted with an SPS 6005 membrane. Stopped-flow microdialysis sampling was found to give the least analyte depletion and thus used for quantitation of the enzymatic hydrolysates. However, CFMS can be used when analyte depletion is not significant (large-volume reactor). Hydrolysis of ivory nut mannan gave mainly mannobiose and mannotriose in almost equal amounts, which is consistent with an endo-wise hydrolysis. The concentrations of mannose and mannopentaose did not change significantly over the monitoring period, however, that of mannotetraose increased gradually up to 11 h where it starts to decrease.