Fig. 5

Fault diagnosis in the abnormal fermentation of glutamate with fault source from the human operation mistake. The mistake was due to NaOH solution was used instead of ammonia water to maintain the pH level during the operation. a the 95 % confidence interval (shaded in green) and mean values (red curve) for glutamate production. The black curve represents the estimated production of glutamate from the fitted GAM using the online recorded data on fermentation parameters from this abnormal experiment. The black dots represent the offline measured production of glutamate from this abnormal experiment. b–g online recorded data on the fermentation parameter (b) carbon dioxide evolution rate (CER), c dissolved oxygen (DO), d oxygen uptake rate (OUR), e pH, f stirring speed (SS) and g temperature (Temp) from this abnormal experiment