Aims: Skim milk agar was developed to investigate extracellular cell-bound
proteinase in yogurt cultures, Streptococcus thermophilus and Lactobacillus
Methods and Results: The Lact. bulgaricus cultures produced more extracellu
lar cell-bound proteinase than did Strep. thermophilus cultures. Strong pos
itive correlations between the size of the exopolysaccharide (EPS) layer an
d extracellular cell-bound proteinase were found for both Streptococcus and
Conclusions: Strong positive linear relationships existed between the EPS s
ize and colony size and the diameter of clear zone and colony size for Stre
ptococcus cultures, whereas weak positive linear relationships were observe
d for Lactobacillus cultures.
Significance and Impact of the Study: These data are useful to validate the
relationship between extracellular proteinase and the EPS size of LAB. Als
o, a convenient medium to detect the presence of extracelluar cell-bound pr
oteinase of LAB is valuable for dairy industries.