Major is BIOCHEMICAL ENGINEERING. the writer who will paraphrase this paper must be have background in biology chemistry and engineering. it is very important that he understand the theory or he will write a very bad paper. this paper talks about the effect of fluid dynamic generated stresses on the plasmid DNA as the plasmid is sensitive to shear and the production of plasmid at commercial scale involve processing the plasmid DNA to many equipment which have high shear rates. shear affect the purity and quality of the plasmid dna as it will cause breakage of (supercoiled isoform) of plasmid. supercoiled form of plasmid need to be in a very high content in order for the plasmid to be approved by FDA to be used for gene therapy application.