Enhanced cyanophycin production by Escherichia coli overexpressing the heterologous cphA gene from a deep sea metagenomic library

Cyanophycin is a non-ribosomally synthesized polymer and its microbial production has attracted increased attention due to its pharmaceutical and chemical values. For the characterization and production of cyanophycin, the cphA49 gene was cloned and expressed in Escherichia coli. Soluble cyanophycin was isolated from the cultures and characterized. The results showed that it was composed of 50% of aspartic acid, 45% of arginine, and 3.5% of lysine, and exhibited a homogenous molecular mass of 35 kDa. To improve soluble cyanophycin production, the induction conditions for cphA49 gene expression were optimized. Meanwhile, the effects of medium content and induction duration on soluble cyanophycin production were also investigated, and the soluble cyanophycin yield reached a maximum at 72 h. Finally, to further increase the soluble cyanophycin production, the cultivation was carried out by supplement of arginine, aspartic acid, lysine and glucose into the minimal resource medium after cphA49 gene expression level was improved under optimized conditions, and the maximum concentration of soluble cyanophycin reached 1.72 g/L.