Base-Controlled Synthesis of Heteroatom-Embedded 9-Membered Cycloalkynes and 6-Membered Sultams through Copper-Catalyzed Cyclization.

A facile copper-catalyzed, base-controlled cyclization reaction has been developed for the synthesis of 9-membered cycloalkyne and 6-membered heterocycle sultams under mild conditions. This protocol utilizes a copper-catalyzed intramolecular A (alkyne-aldehyde-amine) coupling reaction to efficiently synthesize 9-membered cycloalkyne sultams in yields up to 90%. Alternatively, by substituting NaHCO with DBU, the protocol achieves selective deprotection of the -propargyl group, thereby facilitating the formation of 6-membered heterocyclic sultams, also in high yields.

The combination of uridine and nitrogen-deprivation promotes the efficient formation of astaxanthin-rich motile cells in Haematococcus pluvialis.

Astaxanthin accumulation in Haematococcus pluvialis typically occurs alongside the formation of secondary cell wall (SCW), hindering astaxanthin extraction and bio-accessibility. A potential solution lies in cultivating astaxanthin-rich motile cells lacking SCW. This study explored the influence and underlying mechanism of nitrogen-deprivation (ND) on SCW formation and established a connection between pyrimidine metabolism and SCW development.

Enhancement of astaxanthin production, recovery, and bio-accessibility in Haematococcus pluvialis through taurine-mediated inhibition of secondary cell wall formation under high light conditions.

This study explored the use of taurine in enhancing the production and bio-accessibility of astaxanthin in Haematococcus pluvialis, which typically forms a secondary cell wall hindering astaxanthin extraction. The biomass of taurine-treated group significantly increased by 18%, and astaxanthin yield surged by 34% in comparison to the control group. Without cell disruption, astaxanthin recovery from thin-walled cells in the taurine-treated group, using dimethyl sulfoxide and ethanol as extraction reagents, was 97% and 75%, respectively, which were 30-fold higher than those of thick-walled cells in the control group.

Exogenous prolinebooststheco-accumulation ofastaxanthin and biomassin stress-induced Haematococcus pluvialis.

This paper aims to explore the role of proline (Pro) in the production of biomass and astaxanthin (AST) in stress-induced Haematococcus pluvialis. The astaxanthin content and productivity were 24.02 mg g and 2.

Buffering culture solution significantly improves astaxanthin production efficiency of mixotrophic Haematococcus pluvialis.

Sodium acetate (NaAc) supplementation, often used to increase the growth of H. pluvialis under low light, but promotes cell death under high light; its underlying reasons and solutions are rarely reported. Here, NaAc supplementation was found to rapidly increase pondus hydrogenii (pH) of culture solution, elevate reactive oxygen species (ROS), and cause cell death immediately under higher light.

Enhancing astaxanthin and lipid coproduction in Haematococcus pluvialis by the combined induction of plant growth regulators and multiple stresses.

Coupling chemical induction and abiotic stresses is a beneficial strategy for astaxanthin (Asta) induction in Haematococcus pluvialis. The combined application of melatonin (MT) and putrescine (Put) induced Asta and lipid biosynthesis in H. pluvialis under adverse conditions.

Physiological and Metabolomics Analyses Reveal the Roles of Fulvic Acid in Enhancing the Production of Astaxanthin and Lipids in under Abiotic Stress Conditions.

In this study, it was found that fulvic acid (FA) enhanced the contents of astaxanthin and lipids in under high light and nitrogen starvation conditions by 2- and 1.2-fold, respectively. Meanwhile, the carbohydrate and chlorophyll contents were decreased by FA induction, whereas the levels of reactive oxygen species (ROS) and glutathione (GSH) as well as the expression of astaxanthin and lipid biosynthetic genes were increased.