If antagonism was
present, the possible inhibitory action of hydrogen
peroxide was eliminated by the addition of a sterile
solution of catalase (1 mgmL1) at 251C for 30 min. If
inhibition continued to be present when the extract
added to the wells had been neutralized and treated with
catalase, this was taken to be due to the production of
bacteriocins or bacteriocin-like compounds. The proteinaceous
nature of the active extract was evaluated by
treating this extract with a 1 mgmL1 final concentration
of the proteolytic enzymes (Sigma-Aldrich Corporation,
St. Louis, Missouri, USA). These were:
proteinase K (33Umg1), a-chymotripsin (66Umg1),
trypsin (105Umg1) and pepsin (1,730Umg1), in
accordance with Bonade` et al. (2001). Any residual
antimicrobial activity of treated extracts was determined
by the agar well diffusion method.
2.3. Testing
If antagonism waspresent, the possible inhibitory action of hydrogenperoxide was eliminated by the addition of a sterilesolution of catalase (1 mgmL1) at 251C for 30 min. Ifinhibition continued to be present when the extractadded to the wells had been neutralized and treated withcatalase, this was taken to be due to the production ofbacteriocins or bacteriocin-like compounds. The proteinaceousnature of the active extract was evaluated bytreating this extract with a 1 mgmL1 final concentrationof the proteolytic enzymes (Sigma-Aldrich Corporation,St. Louis, Missouri, USA). These were:proteinase K (33Umg1), a-chymotripsin (66Umg1),trypsin (105Umg1) and pepsin (1,730Umg1), inaccordance with Bonade` et al. (2001). Any residualantimicrobial activity of treated extracts was determinedby the agar well diffusion method.2.3. Testing
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