Buffering a media can affect microbial growth which depends upon the composition of the buffer. That's why buffer or any other solution to maintain pH or control foam is added dropwise so as not affect the microbial growth and the process can be completed with minimum addition of foreign components.

Dear Rahul Kumar ,

Thank you for your answer, the components of the buffer will be also utilized by the microbes along with other media components or thee buffer components are non utilizable?

It depends upon the microbe. Suppose the buffer is also action as carbon source then it will be utilised by microbe but quantity of buffer added will be low (volume, drop wise addition) which will be utilised in maintaining the pH rather than microbial growth. Also there is preferential growth in which microbes favours one source of nutrient over another like we choose our food over other being both are present in medium.