Growth and Biochemical Composition Characteristics of Arthrospira platensis Induced by Simultaneous Nitrogen Deficiency and Seawater-Supplemented Medium in an Outdoor Raceway Pond in Winter.

Arthrospira platensis, a well-known cyanobacterium, is widely applied not only in human and animal nutrition but also in cosmetics for its high amounts of active products. The biochemical composition plays a key role in the application performance of the Arthrospira biomass. The present study aimed to evaluate the growth and biochemical composition characteristics of A. platensis, cultured with a nitrogen-free and seawater-supplemented medium in an outdoor raceway pond in winter. The results showed that the biomass yield could achieve 222.42 g m-2, and the carbohydrate content increased by 247% at the end of the culture period (26 d), compared with that of the starter culture. The daily and annual areal productivities were 3.96 g m-2 d-1 and 14.44 ton ha-1 yr-1 for biomass and 2.88 g m-2 d-1 and 10.53 ton ha-1 yr-1 for carbohydrates, respectively. On the contrary, a profound reduction was observed in protein, lipid, and pigment contents. Glucose, the main monosaccharide in the A. platensis biomass, increased from 77.81% to 93.75% of total monosaccharides. Based on these results, large-scale production of carbohydrate-rich A. platensis biomass was achieved via a low-cost culture, involving simultaneous nitrogen deficiency and supplementary seawater in winter.

Halorubrum glutamatedens sp. nov., a Halophilic Archaeon Isolated from a Rock Salt.

An extremely halophilic archaeon, strain ZY8T, was isolated from a rock salt of Yunnan salt mine. It was able to grow at 12-30% (w/v) NaCl (optimum, 15-20%), pH 7.0-9.0 (optimum, pH 8.5), and 20-45 °C (optimum, 42 °C). Sequence similarity search of its 16S rRNA gene showed that strain ZY8T belonged to the genus Halorubrum, and it is closely related to species of H. aethiopicum SAH-A6T (98.6%), H. aquaticum EN-2T (98.6%), and H. halodurans Cb34T (98.5%), respectively. Strain ZY8T contained phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and phosphatidylglycerol sulfate as its major phospholipids, and a sulfated diglycosyl diether as its major glycolipid. The DNA G+C content was 66.7 mol%. DNA-DNA relatedness between strains ZY8T and closely related species were far below 70%. Based on the phenotypic and phylogenetic analyses, it is proposed that strain ZY8T represents a novel species of the genus Halorubrum, for which the name Halorubrum glutamatedens sp. nov. is proposed. The type strain is ZY8T (=CGMCC 1.16026T=NBRC 112866T).

Halorubrum depositum sp. nov., a Novel Halophilic Archaeon Isolated from a Salt Deposit.

A non-motile, pleomorphic rod-shaped or oval, red-pigmented (nearly scarlet), extremely halophilic archaeon, strain Y78T, was isolated from a salt deposit of Yunnan salt mine, China. Analysis of the 16S rRNA gene sequence showed that it was phylogenetically related to species of the genus Halorubrum, with a close relationship to Halorubrum rutilum YJ-18-S1T (98.6%), Halorubrum yunnanense Q85T (98.3%), and Halorubrum lipolyticum 9-3T (98.1%). The temperature, NaCl, and pH ranges for growth were 25-50 °C, 12-30% (w/v), and 6.5-9.0, respectively. Mg2+ was required for growth. The polar lipids of strain Y78T were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, and a sulfated diglycosyl diether. The DNA G+C content was 66.6 mol%. DNA-DNA hybridization values between strain Y78T and two closely related species of the genus Halorubrum were far below 70%. Based on the data presented in this study, strain Y78T represents a novel species for which the name Halorubrum depositum sp. nov. is proposed; the type strain is Y78T (= CGMCC 1.15456T = JCM 31272T).