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. Adjusting pH of NaAc supplemented culture solution with 10 mM Tris-HCl once before high light significantly reduced cell mortality and increased astaxanthin yield. When verified in a 5-litre photobioreactor, this novel method produced over 4.0% of dry weight (DW) astaxanthin within only 8-10 days. In summary, this study explained reasons underlying NaAc supplementation-induced cell death and provided an rapid, easy and effective method to produce high amount of astaxanthin in H. pluvialis.

Metabolic dynamics and physiological adaptation of Panax ginseng during development.

KEY MESSAGE: The dynamics of metabolites from leaves to roots of Panax ginseng during development has revealed the tissue-specific and year-specific metabolic networks. Being an essential Oriental medicinal plant, ginseng (Panax ginseng Meyer) is a slow-growing perennial herb-accumulating pharmaceutically active metabolites such as ginsenosides in roots during growth. However, little is known about how ginseng plants survive in the harsh environments such as winter cold and summer heat for a longer period and accumulates those active metabolites as the plant grows. To understand the metabolic kinetics in both source and sink organs such as leaves and roots of ginseng plant, respectively, and to assess the changes in ginsenosides biosynthesis during ginseng growth, we investigated the metabolic profiles from leaves and roots of 1-, 4-, and 6-year-old field-grown ginseng plants. Using an integrated non-targeted metabolomic approach, we identified in total 348 primary and secondary metabolites, which provided us for the first time a global metabolomic assessment of ginseng during growth, and morphogenesis. Strikingly, the osmoprotectants and oxidized chemicals were highly accumulated in 4- and 6-year-old ginseng leaves suggested that ginseng develop a wide range of metabolic strategies to adapt unfavorable conditions as they mature. In 6-year-old plants, ginsenosides were decreased in leaves but increased in roots up to 1.2- to sixfold, supporting the view that there is a long-distance transport of ginsenosides from leaves to roots as ginseng plants mature. Our findings provide insights into the metabolic kinetics during the development of ginseng plant and this could complement the pharmacological importance of ginseng and its compounds according to their age.

Molecular analysis of a UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) gene from purple potato (Solanum tuberosum).

In anthocyanin biosynthesis, UDP-glucose: anthocyanidin 3-O-glucosyltransferase (UFGT) catalyzes the transfer of the glucosyl moiety from UDP-glucose to the 3-hydroxyl group of anthocyanidins, producing the first stable anthocyanins. The full-length cDNA of UFGT (designated as StUFGT) was isolated and characterized from Solanum tuberosum. The full-length cDNA of StUFGT was 1536 bp containing a 1344 bp open reading frame (ORF) encoding 448 amino acids with a calculated molecular mass of 49.9 kDa and an isoelectric point of 5.62. Comparative and bioinformatic analyses revealed that StUFGT has extensive homology with UFGTs from other plant species. Phylogenetic analysis indicates that StUFGT belongs to the plant UFGT cluster. StUFGT was found to be expressed in roots, stems, leafstalks and leaves. Expression profiling analysis revealed that StUFGT expression was induced correspondingly by exogenous elicitors including gibberellic acid and sucrose, suggesting that UFGT might play a regulatory role in anthocyanin biosynthesis in Solanum tuberosum at the transcriptional level.