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Microalgae are important biological resources which attract the researchers for the production of valuable products like bio-energy and value-added products. In this study, enhanced accumulation of carotenoids and lipids was obtained from Coelastrella sp. M60 which was grown at 40 °C, along with different stress conditions (nitrogen starvation, salinity and TiO2). The results clearly indicate that osmotic stress and nitrogen starvation along with high temperature had induced the yield of zeaxanthin (13.15 mg/g DCW) and the lipid content (39.51 ± 5.13%). Further, it was also observed that TiO2 combined with other stresses had induced the increased accumulation of astaxanthin and zeaxanthin up to 1.16 and 0.51 fold on the 10th day of cultivation. On the contrary, TiO2, along with other stress conditions had influenced the biomass production up to 1.16 fold than the control, but no detectable increase in lipid content was observed. Thus, for the first time it is reported that by employing combined stress factors such as high temperature, nitrogen starvation and 3% salinity had resulted in significant improvement in zeaxanthin production in the foresaid microalgae. Further, it was also noticed that the Coelastrella sp. M60 had accumulated the carotenoids and lipids under TiO2 along with other oxidative stress conditions within the short duration.

The asymmetric unit consists of a 2,4-di­amino-6-phenyl-1,3,5-triazin-1-ium cation and a 4-methyl­benzoate anion. The protonated nitro­gen and amino group nitro­gen atoms are involved in hydrogen bonding with the sulfonate oxygen atoms through a pair of inter­molecular N—H⋯O hydrogen bonds. The inversion-related mol­ecules are further linked by four N—H⋯O inter­molecular inter­ations to produce a complementary DDAA hydrogen-bonded array. Hirshfeld surface analysis was employed to further examine the inter­molecular inter­actions., In the title mol­ecular salt, C9H10N5 +·C7H7O3S−, the asymmetric unit consists of a 2,4-di­amino-6-phenyl-1,3,5-triazin-1-ium cation and a 4-methyl­benzene­sulfonate anion. The cation is protonated at the N atom lying between the amine and phenyl substituents. The protonated N and amino-group N atoms are involved in hydrogen bonding with the sulfonate O atoms through a pair of inter­molecular N—H⋯O hydrogen bonds, giving rise to a hydrogen-bonded cyclic motif with R 2 2(8) graph-set notation. The inversion-related mol­ecules are further linked by four N—H⋯O inter­molecular inter­actions to produce a complementary DDAA (D = donor, A = acceptor) hydrogen-bonded array, forming R 2 2(8), R 4 2(8) and R 2 2(8) ring motifs. The centrosymmetrically paired cations form R 2 2(8) ring motifs through base-pairing via N—H⋯N hydrogen bonds. In addition, another R 3 3(10) motif is formed between centrosymetrically paired cations and a sulfonate anion via N—H⋯O hydrogen bonds. The crystal structure also features weak S=O⋯π and π–π inter­actions. Hirshfeld surface and fingerprint plots were employed in order to further study the inter­molecular inter­actions.

The co-crystal structure of 2,4-diamino-6-phenyl-1,3,5-triazine with 4-chlorobenzoic acid/4-methoxybenzoic acid molecules are explain the link between the dimension and shape of their hydrogen-bond...

In the crystal structure, the cations form hydrogen-bonded zigzag chains through centrosymmetric cyclic (8) N—H⋯N associations while the water mol­ecule acts as a double acceptor, linking the cations of the chain peripherally through amine N—H⋯O hydrogen bonds, closing cyclic (8) motifs, and as a double O—H⋯O donor, linking the anions, giving an overall three-dimensional structure., The asymmetric unit of the title mol­ecular salt, C4H8N5 +·C2Cl3O2 −·H2O, coomprises a 2,4-di­amino-6-methyl-1,3,5-triazin-1-ium cation, a tri­chloro­acetate anion and a water mol­ecule of solvation. The protonated N atom of the cation forms a hydrogen bond with a carboxyl O atom of the anion, which also acts as a hydrogen-atom acceptor with the water mol­ecule. The cations form centrosymmetric dimeric units through R 2 2(8) N—H⋯N bond pairs and are extended into zigzag chains along the c-axis direction, also through similar cyclic R 2 2(8) dual N—H⋯N hydrogen-bonding inter­actions. The water mol­ecule acts as a dual acceptor forming N—H⋯O hydrogen bonds between the amine groups of the cations, forming cyclic R 2 3(8) motifs. The second H atom of the water mol­ecule also acts as a donor in an O—H⋯O hydrogen bond with the second carboxyl O atom, linking the chains along the b-axis direction. These interactions give rise to an overall three-dimensional supra­molecular structure. A Hirshfeld surface analysis was employed in order to study the inter­molecular inter­actions.

Biofuels from microalgae are being considered as an alternate renewable energy to fossil fuels, which could extinct by the year 2050 due to its exhaustive usage. Microalgae are tiny cell factories that accumulate large amount of lipids under nutrients starvation, which are sustainable sources for biofuels production. In this study, hydrolysate of lignocellulosic biomass (LCB) was used as a carbon source to improve the production of microalgal biomass, which was further subjected to nitrogen starvation for the enhanced lipid accumulation. The lipid content of LCB supplement 3% and 2% grown cultures of Dictyococcus sp. VSKA18 and Coelastrella sp. M-60 were 44% and 52%, respectively. Further, recovery of fatty acid methyl esters (FAME) was achieved using two different catalysts such as acid (homogeneous) and iron nanoparticles (heterogeneous) synthesized using Sargassum polycystum. Moreover, the saturated fatty acid (SFA) of Dictyococcus sp. VSKA18 and Coelastrella sp. M-60 supplemented with 3% of LCB hydrolysates along with N starvation had yielded 90% and 28% respectively. Fuel quality parameters were also analyzed and compared with ASTM and European standards. Thus, the synthesized bio-iron nanoparticles mediated FAME conversion would be a suitable choice for improving biodiesel production.

In the title compound, [Nd(NO3)3(H2O)4]·3C3H4N4, neodymium is ten-coordinate with a distorted bicapped square-antiprismatic geometry formed from six O atoms from three nitrate ions and four O atoms from four coordinated water molecules. The structure also contains neutral 3-amino-1,2,4-triazine molecules which are not coordinated to the central metal atom. The coordinated water molecules and nitrate ions of adjacent complexes are linked by O—H...O hydrogen bonds to form cyclic R 2 2(8) ring motifs, which in turn are further connected via hydrogen bonds to generate a sheet-like structure. The triazine molecules are involved in a number of hydrogen-bonding interactions: N—H...N and O—H...N interactions to form R 3 3(9) motifs and N—H...N interactions to link the organic molecules into chains. Weak C—H...O hydrogen bonds also occur between triazine molecules and coordinated nitrate atoms. All these intermolecular contacts contribute to the stabilization of the three-dimensional supramolecular framework. Hirshfeld surface analysis shows that N...H/H...N and H...H interactions account for 42.9 and 20.6% of the surface, respectively.

In the title molecular salt, C5H9N4+·C13H10NO2−·C5H8N4, the asymmetric unit consists of a 6-amino-3,4-dimethyl-1,2,4-triazin-1-ium cation, a 2-anilinobenzoate anion and a neutral 3-amino-5,6-dimethyl-1,2,4-triazine molecule. The typical intramolecular N...H—O hydrogen bond is observed in the 2-anilinobenzoate anion. In the crystal, the protonated N atom and the 3-amino group are hydrogen bonded to the carboxylate oxygen atomsviaa pair of N—H...O hydrogen bonds, forming anR22(8) ring motif. These motifs are further linked with adjacent neutral 3-amino-5,6-dimethyl-1,2,4-triazine molecules by N—H...O and N—H...N hydrogen bonds to produce centrosymmetric six-membered units, enclosingR22(8) andR34(9) ring motifs. They are reinforced by a C—H...N hydrogen bond and stack up theb-axis direction.

In the hydrogen phthalate anion of the title molecular salt, C6H10N3O+·C8H5O4−, the dihedral angles formed by the benzene ring and the mean planes of the –COOH and –COO−groups are 16.1 (3) and 19.8 (3)°, respectively. There is an intramolecular O—H...O hydrogen bond in the anion generating anS(7) ring motif. In the crystal, the protonated N atom of the pyrimidinium ring and the 2-amino group of the cation are hydrogen bonded to the carboxylate O atoms of the anionviaa pair of N—H...O hydrogen bonds, forming anR22(8) ring motif. The ion pairs are further connectedviaN—H...O and C—H...O hydrogen bonds, forming ribbons parallel to the [01-1] direction. The ribbons are linked by off-set π–π stacking interactions [intercentroid distances = 3.8279 (16) and 3.6074 (15) Å], forming a three-dimensional structure.