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

Quantitative aspects of on-line microdialysis sampling are investigate d 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 st opped-how microdialysis sampling with stopped stirring were investigat ed as a possible means for studying bioprocesses. The hydrolytic prope rties of a well characterised endomannanase from Aspergillus niger wer e studied using 0.01% ivory nut mannan as substrate in a 5-ml reaction vessel. On-line sampling was achieved using a microdialysis probe fit ted with an SPS 6005 membrane. Stopped-flow microdialysis sampling was found to give the least analyte depletion and thus used for quantitat ion of the enzymatic hydrolysates. However, CFMS can be used when anal yte depletion is not significant (large-volume reactor). Hydrolysis of ivory nut mannan gave mainly mannobiose and mannotriose in almost equ al amounts, which is consistent with an endo-wise hydrolysis. The conc entrations of mannose and mannopentaose did not change significantly o ver the monitoring period, however, that of mannotetraose increased gr adually up to 11 h where it starts to decrease.