Effect of Acyl Homoserine Lactone on Recombinant Production of Human Insulin-like Growth Factor-1 in Batch Culture of Escherichia coli.

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 production.
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.
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