@ Ajay, bacteria grow well between pH 6.5-7.0. But bacteria like E. coli can grow well even at alkaline pH like 8.0. To check the pH of E.coli culture, place the tip of the flat pH electrode on the surface of the culture medium sample. Make sure that the tip touches the culture medium and no gap between them. Record the pH and temperature displayed on the meter once stable. If you need to adjust the pH of cell culture medium, use 1 N NaOH to raise the pH or 1 N HCL to lower the pH. Be very careful to only add a drop at a time because it is very easy to over-adjust the pH. You could try using a lower concentration of acid and base