Incase you have a BTech in Biotechnology, you may skip MTech directly for a PhD in Biotechnology in India (Valid Gate Score Required) and definitely in Universities Abroad, especially in Countries like US. Definitely you may even pursue a MTech in Biotechnology after BTech, thats always an option or may MTech in some relatable Engineering stream from some of the Higher Technical Institutions like Top IITs or IISc Bangalore. However, In India apart from these Top Institutes most central Universities demand a Masters followed by PhD.

However, if your degree in BSc in Biotechnology, you may require going for Masters followed by PhD in the respective subject or field of interest.

For youre case having done MSc in Zoology, with a Valid GATE Score in Biotechnology, I believe youll be able to apply to Higher Technical Institutes in India for PhD.