In glutamate fermentation

initial biotin content in the medium varies with the corn slurry originating sources or even production batches

and this variation affects fermentation performance and stability.In this study

activities changes of the key enzymes at metabolic nodes of pyruvate

isocitrate and α-ketoglutarate when initial biotin content was at normal/improper levels

particularly when initial biotin content was at improper levels but adopting faults-rescue measures during fermentation were carefully investigated.When initial biotin was in shortage

all activities of the key enzymes responsible for catalyzing the main glutamate synthesis route were weakened

in particular

the activity of α-oxoglutamate dehydrogenase complex was inactivated and energy metabolism completely relied on glyoxylate cycle.When biotin in shortage was determined and biotin was supplemented

the enzyme responsible for the central metabolic route

pyruvate dehydrogenase returned to the normal level

and TCA cycle turned to be the main energy metabolism route once again.On the other hand

when initial biotin was in excess

all activities of the key enzymes were activated except pyruvate carboxylase and glutamate dehydrogenase. When biotin in excess was determined and Tween 40 was supplemented

the activities of two key enzymes responsible for glutamate synthesis

pyruvate dehydrogenase and isocitrate dehydrogenase

remained at high levels.At the same time

activities of α-oxoglutamate dehydrogenase complex and isocitrate lysase declined to the normal levels.The final glutamate concentration of the failure-likelihood fermentations could be recovered back to the control level (75—80 g·L-1)by using the relevant rescue measures.Furthermore

final glutamate concentration could be further increased and reach 87 g·L-1

which was over 108.8% of that obtained in the control case

when adopting the “two-stage” optimal operation mode based on combined adjustment of initial biotin content and Tween 40 addition.