In order to apply for a PhD in Biotechnology from an overseas university, you will need to fulfill the university's individual admission requirements. These may vary from university to university, but there are few requirements that are generally common for all PhD programs in Biotechnology irrespective of the university:

1. You will need to give the GRE general exam. Details for this exam as well as articles on preparation and study tips can be available here. Preparation for a candidate who has knowledge of 10th level mathematics can generally prepare for the GRE exam within 2-3 months of self study or 1-2 months of coaching classes.

2. In addtition to the GRE general exam, many of the top universities require their PhD candidates to submit the scores of GRE subject tests in either Biology, Chemistry. Computer Science, Physics or Biochemistry. This is generally not a hard and fast requirement but often the scores of the subject tests play a great role in boosting your entire application and are highly scrutinized by the admissions committee.

3. An English language proficiency test is always required by any foreign university if your first language is not English. Either the IELTS or TOEFL test scores can be submitted to most universities although you should check the individual university requirement in case they require a single particular test score.

For PhD programs, teaching experience is often part of the course duration and therefore English language proficiency scores need to be good. For the top universities, the minimum TOEFL requirement is 100+ and the minimum IELTS requirement is 7+.

4. The GPA required for admission to the top PhD programs is in the range of 3.0-4.0 on a 4.0 scale. Again, these are not hard and fast requirements but it would be preferred if you have a GPA in this range.

Considering your percentage, conversion of this percentage can vary from university to university. According to one of the most followed conversion methods, a 60-100% score in an Indian university would be equivalent to a 4.0 GPA. Another scale follows the criteria in which an 80-89% would be convertible to a 3.3 GPA ensuring that your score falls in the requisite range. Despite this, some universities follow the 10 point GPA conversion which would entail a much lower 4.0 GPA. Universities often don't disclose their method of GPA conversion and take your transcripts from the previous college according to which conversion is carried out. It's highly probable that your GPA will be converted according to the first methodology and therefore, this is one aspect of your application that you would not need to worry about.

The remaining application materials such as essays and letters of recommendation also hold a large weight in the admission procedure. Therefore it is integral to ensure that your recommendors are properly acquainted with you and your work and also check and recheck the grammar and sentence structure of your essays before submitting them finally through the application portal.