Abstract:Recombinant phycobiliproteins were expressed in Escherichia coli. The overexpressed phycobiliproteins were isolated and purified, and their spectral properties and antioxidant activities were determined. The optimal conditions for the induction of recombinant phycobiliproteins with isopropyl-beta-D-thiogalactopyranoside (IPTG) were identified as following: adding 0.1 mmol/L of IPTG and 5 mmol/L of 5-aminolevulinic acid (5-ALA) into the growth medium at an optical density at 600 nm (OD600) of 0.95 and then incubating the cells at 18 ℃ for 24 h. Under these conditions, the expression level of the phycobiliproteins was 149.5 mg/L. The optimal conditions for the induction of recombinant phycobiliproteins with lactose were adding 1.0 g/L of lactose and 5 mmol/L of 5-ALA to the bacterial culture at an OD600 of 1.2, followed by incubation at 18 ℃ for 26 h. The expression level in this case was 120.9 mg/L. The recombinant phycobiliproteins exhibited maximum absorbance at 550 nm and maximum emission at 562 nm. Compared to recombinant proteins obtained upon induction by IPTG, the recombinant proteins obtained upon induction by lactose had a higher absorbance at 550 nm, higher fluorescence emission at 562 nm, and higher hydroxyl radical and superoxide anion-scavenging activities.
