在活跃链霉菌中过表达根瘤菌血红蛋白基因以提高那那西肽产量

Oxygen deficiency is a critical limiting factor for nosiheptide production in Streptomyces actuosus during fermentation. To alleviate oxygen limitation and enhance the yield of nosiheptide, hemoprotein from Sinorhizobium meliloti (SmHb) was overexpressed in S. actuosus with overexpression of hemoglobin from Vitreoscilla (VHb) as a positive control. The successful expression of SmHb and VHb in S. actuosus was confirmed by SDS-PAGE and CO-difference spectra analysis. The results showed that S. actuosus recombinant strain with SmHb expression improved nosiheptide production by 138% compared with the wild strain (WT) under the low aeration condition, which was similar to S. actuosus mutant strain with VHb expression. Furthermore, two copies of SmHb gene were integrated in S. actuosus, which further increased the nosiheptide production by approximately 1.9-fold higher than original strain, and final concentration of nosiheptide was up to 2352 μg/mL. These results suggested that engineering of SmHb could be used as an efficient method for constructing a high nosiheptide-accumulating strain.