The top colleges for BSc Biotechnology in Tamilnadu are:

• PSG College of Arts and Science, Coimbatore
• Stella Maris College, Chennai
• Sri Krishna Arts and Science College, Coimbatore
• Women's Christian College, Chennai
• Bishop Heber College, Tiruchirappalli
• Lady Doak College, Madurai
• SRC College Trichy - Seethalakshmi Ramaswami College
• Nehru Arts and Science College, Coimbatore
• Guru Nanak College, Chennai

For more details you may visit the link provided below :

https://university.careers360.com/colleges/list-of-bsc-in-biotechnology-degree-colleges-in-tamil-nadu

All this colleges are best in itself. If you get admission in any of them you may be sure that you will get the good quality education.

I hope my answer helps. All the very best for your future endeavors!