ONPG is one of the important biochemical tests for biochemical identification of unknowns. Which test can replace it?
Dear Bahaa, The 'ONPG test' is used to differentiate lactose fermenters from non-fermenters, and assays beta-galactosidase activity. The value of using ONPG (ortho-nitrophenyl-b-D-galacto-pyranose) is that when it is hydrolysed, the product (ortho-nitrophenol) is chromogenic (yellow) and can be quantified easily by spectrophotometry. An alternative to this type of biochemical test would be to incubate bacteria in minimal medium or agar containing lactose as the sole carbon source (a further alternative would be to use general nutrient medium containing ONPG or a similar substrate such as XGAL in which you would look for coloured colonies rather than growth/no growth). This type of culturing approach could be very useful to screen a large number of isolates before quantifying lactose use by ONPG assays. Regards, Andrew.
Dear Sir
you can using lactose broth test, It s very simple test ,bacteria grow in lactose broth after 24 show grow by spectrophotometer than standard sample at 600nm
Dear Lamiaa, this will be ok in case of lactose fermenting bacteria, what will be the case if no fermentation occurs?
Pale yellow colonies appear in case of non-lactose fermenting bacteria. MacConkey agar is selective and differential medium.
This answer leads us to another question, is lactose could be utilized only by fermentation or can be utilized by oxidative mean as well?
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