Spermidine-induced recovery of human dermal structure and barrier function by skin microbiome.

An unbalanced microbial ecosystem on the human skin is closely related to skin diseases and has been associated with inflammation and immune responses. However, little is known about the role of the skin microbiome on skin aging. Here, we report that the Streptococcus species improved the skin structure and barrier function, thereby contributing to anti-aging. Metagenomic analyses showed the abundance of Streptococcus in younger individuals or those having more elastic skin. Particularly, we isolated Streptococcus pneumoniae, Streptococcus infantis, and Streptococcus thermophilus from face of young individuals. Treatment with secretions of S. pneumoniae and S. infantis induced the expression of genes associated with the formation of skin structure and the skin barrier function in human skin cells. The application of culture supernatant including Streptococcal secretions on human skin showed marked improvements on skin phenotypes such as elasticity, hydration, and desquamation. Gene Ontology analysis revealed overlaps in spermidine biosynthetic and glycogen biosynthetic processes. Streptococcus-secreted spermidine contributed to the recovery of skin structure and barrier function through the upregulation of collagen and lipid synthesis in aged cells. Overall, our data suggest the role of skin microbiome into anti-aging and clinical applications

Supercritical CO2 compressor operation near stall and surge conditions

Instabilities such as stall and surge have been widely studied in open loop gas turbine system for several decades. However, researches on instabilities in a closed loop are limited. Especially, no experimental investigation in a supercritical CO2 compressor has been performed thoroughly before. An integral test loop equipped with a turbo-alternator-compressor using active magnetic bearing was utilized to study the instabilities in a supercritical CO2 compressor. The compressor performance testing was conducted including near stall and surge operating conditions. The mass flow rate of compressor was greatly reduced even beyond surge limit and pressure was measured with high frequency transducer to observe the characteristics. It was observed that as the inertia of the system was changed by altering the compressor inlet conditions, the characteristics of the supercritical CO2 compressor in unstable operating conditions also vary. This can be qualitatively explained by using the theory Greitzer proposed previously