This product is not recombinant. It is native holo-Transferrin from human plasma. The material is isolated by ammonium sulfate precipitation on plasma, followed by column chromatography purification steps. However, the compound has not been affinity purified and there is no additional testing to determine the presence of trace impurities. Please see an example or lot-specific Certificate of Analysis at the link below:
https://www.sigmaaldrich.com/product/sigma/t4132#product-documentation
Please see the link below to review the product datasheet:
https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/documents/130/436/t4132pis.pdf