Abstract:

Near infrared spectroscopy (NIR) combined with partial least square (PLS) was used to develop a new method for the real
time monitoring of the intracellular polysaccharide concentration during the Cordyceps militaris fermentation. 39 batches of Cordyceps militaris fermentation were implemented under various fermentation conditions in 5 L at three kinds of different  conditions. The samples were collected at intervals of some hours after the fermentations running into the exponential growth phase. The NIR spectra of the samples were recorded and the intracellular polysaccharide mass concentrations of the samples were determined at the same time via the reference method. PLS method was used to model the relationship between the NIR and the intracellular polysaccharide mass concentration.  The developed model was optimized by selecting the suitable spectral preprocessing method and the suitable number of latent variables. The relation coefficient of the predictive values obtained by leaveoneoutcrossvalidation method and the reference values (R) was 0875 0 and the root mean square error of crossvalidation (RMSECV) was 0.305 2. Using this model for predicting the intracellular polysaccharide concentration in samples, the root mean square error of calibration samples (RMSEC) was 0.167 0 and the root mean square error
 of prediction samples (RMSEP) was 0.365 0. These results demonstrate that the stability and the predictive capability of this model were satisfied and this method should be popular in fermentation monitoring processing.

Key words:  near infrared spectroscopy, partial least square, Cordyceps militaris, intracellular polysaccharide