The study aims to produce Expansin protein isolated from a young tomato plant by using Escherichia coli which is used in recombinant protein production. Continuous culture is the most common method used to grow cells for recombinant protein production. In the study, the K12 strain of E. coli was used as a culture for the production of Expansin protein. The used LeExp1 gene was isolated from a young tomato plant. Since the related gene is found in very small amounts in plants, it has been reproduced using the PCR method and has been made workable with this method. T17 vector (T7 RNA polymerase system), which is frequently used in the production of recombinant protein, was used as the bacterial expression vector. The T7 RNA polymerase system is a commonly used vector in E. coli. With the transfer, the E. coli bacterium was given the ability to produce recombinant protein. Whether the obtained recombinant protein expressed the appropriate protein was determined by SDS Page analysis.