Complex sentence: The limiting factor for the use of microorganisms like "E. coli" in biosynthesis of gene products like insulin is time, yet due to advancements in the synthesis of oligonucleotides and liquid chromatography, the production time needed for DNA fragments has greatly decreased.
Split into simpler sentences: The limiting factor for the use of microorganisms like "E. coli" in biosynthesis of gene products like insulin is time. Yet due to advancements in the synthesis of oligonucleotides and liquid chromatography, the production time needed for DNA fragments has greatly decreased.