Amino acid decarboxylase(AAD)is a key enzyme in biogenic amine synthesis.Microbial AAD is generally an intracellular enzyme,but its properties are stable and it can still maintain catalytic activity in extracellular systems.In this paper,with crude enzyme solution obtained from three microbial cells with the ability to produce biogenic amines after ultrasonic disruption as the object,the effects of precursor amino acid concentration,pH and salt concentration on the catalytic activity of in vitro AAD are investigated.The results show that in most cases,the precursor amino acids are not fully converted into biogenic amines,but low concentrations of precursor amino acids significantly reduce the catalytic activity of in vitro AAD.The catalytic activity of AAD of Lactobacillus plantarum 1-8 and Escherichia coli BA-1 is the strongest when pH is 6,while the catalytic activity of AAD of Debaryomyces hansenii MB-1Y is the strongest when pH is 5.The increase of salt concentration leads to the decrease of the catalytic activity of AAD.This study can provide references for exploring the catalytic characteristics and controlling of AAD in food fermentation.
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