Temperature-driven metabolic acceleration independent of cell growth enables high-level production of D-ribulose and shinorine in Streptomyces lividans.

backgroundTemperature strongly influences cellular metabolism through its effects on enzyme activity. Although the optimal growth temperature generally reflects the collective temperature dependence of enzymes involved in proliferation, the optimal temperature for metabolite production may differ from that for cell growth. Streptomyces lividans is regarded as a preferred host for heterologous gene expression to produce recombinant proteins and secondary metabolites via the introduction of biosynthetic gene clusters (BGCs). However, its primary metabolism and the effects of temperature on it have not been well studied.

resultsWe found that S. lividans exhibited enhanced glucose consumption at elevated temperature, even under conditions where many cells were non-viable. At 40 °C, the glucose consumption rate increased by 45% compared to 28 °C, the conventional optimal growth temperature, although the colony-forming unit count at 40 °C was less than one-tenth of that at 28 °C. The elevated temperature drastically reduced cell length and increased the proportion of dead cells observed by fluorescence microscopy. Moreover, we, for the first time, observed that S. lividans produced the rare sugar D-ribulose, and its production was strongly enhanced by temperature elevation. At 40 °C, D-ribulose concentration reached 19.4 g/L, with a sevenfold increase and a yield of 7.3% (g/g-glucose). Using xylose as a carbon source further improved the yield to 9.5% (g/g-xylose). As D-ribulose is synthesized via the pentose phosphate pathway, we metabolically engineered S. lividans to produce the sunscreen metabolite shinorine, which is synthesized from D-sedoheptulose 7-phosphate in the pentose phosphate pathway. Shinorine production was maximized at 34 °C, reaching 762 mg/L, an 11-fold increase compared to that at 28 °C.

conclusionsThis study reveals that S. lividans exhibits enhanced glucose consumption and metabolite production at elevated temperatures, even under conditions of extensive cell death. We identified S. lividans as a novel producer of the rare sugar D-ribulose and successfully engineered it for high-level shinorine production under elevated temperature conditions. These findings highlight the potential of S. lividans as a promising host for the production of primary and secondary metabolites derived from the pentose phosphate pathway.