Hello aspirant
Hope you are doing

Biotechnology is a field which contains an amalgamation of many streams, namely mathematics, chemistry, biology and technology.

Unfortunately , you can't do phd in biotechnology after doing Msc in environmental science as -
The candidates must complete their post-graduation in Biotechnology or Bioinformatics or any other relevant discipline from a recognized board or university in order to do Phd from biotechnology.

According to this you are not eligible.

Here's a link for further information
https://www.careers360.com/courses/biotechnology-course


Hope it helps
Thank you