الفهرس 
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Abstract
The aim of the fir at part of this study was to give detailed information concerning the composition and localization of the eaterase and lipase systems of lactobacille from the thermobacterium group. Conclusions drawn from this investigation are summarized as follows:
1” ^.b-tiyeticus. L.bulgarious, L.laotia and L.acidopfailua strains were capable to produce active esterases. As a general rule the rate of substrate hydrolysis decreased with increasing the number of carbon atoms in the substrate, it was generally noticed that the P-nitrophenyl derivatives were hydrolyzed faster than the 0-nitrophenyls.
2- The electrophoretic study revealed the presence * of up to 5 distinct esteraaes in the different species. The specificity of each band waa
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clearly obtained. The HJ? value for the enzyme and their numbera aeetaa to be apeciea apecific and in some cases differences ara reported for strains of the same apeciea.
>- maximum growth and activities for L.helveticua occurea at the early stationary phaae, followed by some decreaae in activities at the end of the stationary phaae. I1 hat decreaae in enzyme activities is probably due to the further decreaae in pH as an influence of tne physiological age during the stationary phaae.
4- ihe eateraaea of tne lactobacillua are free cytoplasmic enzymes since very little activity was detected on cell debria and no riboaomal activity could be measured.
- juactobaciili from the thermobacterium group showed weak lipolysis siince up to ^4 hr. were neeaeu to detect substrate nydrolyais. i’he -rate of substrate hydrolysis was generally in