in MPN count for coliform bacteria.
i used double strength MacConkey’s broth.
the positive reaction is the change in colour, purple to yellow and gas production.
but some tubes turned to white.
please reply why this white colour is formed?
when these tubes are plated on MacConkey’s agar, they produced Non-lactose fermentor colonies, they are like Pseudo.
yellow colour, because of lactose fermetation, acid produced reacts with the indicator and the colour changes.
but i don’t know changing to white colour.
MaC broth has only lactose as carbon source, i think.
is there other that serves as carbon source, such as Peptone?