Background: IGF-I as a human growth factor produced in Escherichia coli is a single,
non-glycosylated, polypeptide chain containing 70 amino acids and having a molecular mass of 7.6
kDa. Up to now, E. coli expression system has been widely used as the host to produce rhIGF-1
with high yields. Acyl Homoserine Lactones (AHLs) are intercellular signaling molecules used in
quorum sensing by Gram-negative bacteria. Quorum sensing is a cell density-dependent gene regulation
process that allows bacterial cells to express specific genes only when signaling molecules
reach the sufficient concentration.
Objective: For the first time, this study focuses on the N-hexanoyl-L- Homoserine Lactone (HHL)
activity on increasing the cell growth and rh-IGF-1concentration in batch culture of E. coli.
Method: The maximum production of rhIGF-I was previously optimized in 32y culture medium at
32°C with 0.05 mM IPTG as inducer and 10 g/l glucose concentration. Under this condition, different
amounts of HHL (0.001 µg/ml, 1 µg/ml, and 100µg/ml) were evaluated as an inducer for IGF-1
Results: Generally, with increasing of HHL concentration, an increase in dry cell weight (2.45
mg/ml to 4.63 mg/ml) and IGF-I expression level (0.4 mg/ml to 0.77 mg/ml) was observed.
Conclusion: HHL or other types of AHLs can be considered as protein production inducer in bacterial
expression systems through the quorum sensing pathways.