Comparative metabolic profiling-based improvement of rapamycin production by Streptomyces hygroscopicus

Abstract

Rapamycin is a clinically important macrocyclic polyketide with immunosuppressive activity produced by Streptomyces hygroscopicus. To rationally guide the improvement of rapamycin production, comparative metabolic profiling analysis was performed in this work to investigate the intracellular metabolic changes in S. hygroscopicus U1-6E7 fermentation in medium M1 and derived medium M2. A correlation between the metabolic profiles and rapamycin accumulation was revealed by partial least-squares to latent structures analysis, and 16 key metabolites that most contributed to the metabolism differences and rapamycin production were identified. Most of these metabolites were involved in tricarboxylic acid cycle, fatty acids, and shikimic acid and amino acids metabolism. Based on the analysis of key metabolites changes in the above pathways, corresponding exogenous addition strategies were proposed as follows: 1.0g/L methyl oleate was added at 0h; 1.0g/L lysine was added at 12h; 0.5g/L shikimic acid was added at 24h; 0.5g/L sodium succinate, 0.1g/L phenylalanine, 0.1g/L tryptophan, and 0.1g/L tyrosine were added at 36h, successively, and a redesigned fermentation medium (M3) was obtained finally on the basis of M2. The production of rapamycin in M3 was increased by 56.6% compared with it in M2, reaching 307mg/L at the end of fermentation (120h). These results demonstrated that metabolic profiling analysis was a successful method applied in the rational guidance of the production improvement of rapamycin, as well as other industrially or clinically important compounds.