Putrescine is a catabolic product of ornithine or arginine pathways
and can be converted to spermidine that can form spermine.
Lb. bulgaricus apart from three isolates produced lower than 35 mg/
L of putrescine, which is in accordance with the results reported
by Kuley and Ozogul (2011). Putrescine production by S. thermophilus
isolates was below 50 mg/L. Some isolates of S. thermophilus
did not accumulate spermidine (2 isolates) and spermine (9 isolates),
resulting in low amounts of spermidine and spermine
accumulation.