First, the activity of branched-chain transaminase was measured by
incubating CFE with leucine and an excess of the co-substrate,
α-ketoglutarate. The transaminase activity was found to be present in
all microorganisms tested (Fig. 3A). The highest variation was observed in the Lactobacillus genus. L. lactis spp. and Streptococcus thermophilus
showed the highest specific transaminase activity towards leucine and
therefore potentially produce the highest concentrations of
α-ketoisocaproic acid, which is the substrate for the formation of
3-methylbutanal.
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