A computational study of adsorption of divalent metal ions on graphene oxide

Adsorption of divalent metal ions (Pb2+,Cd2+, Zn2+,Cu2+) on graphene oxide (GO) was studied using density functional theory (DFT). Adsorption geometries and energies, as well as the nature of the binding energy, were calculated for the interaction of divalent metal ions with oxygen-containing groups on the surface of GO. The configurations of the complexes were modeled by placing the divalent metal ions above the center and perpendicular to the surface. Binding of Cu2+ to the GO sheet was predicted to be much stronger than that for other divalent metal ions. Calculated results show good agreement with experimental observations and provide useful information for environmental pollution cleanup

Genomic Insight and Optimization of Astaxanthin Production from a New <i>Rhodotorula</i> sp. CP72-2

Astaxanthin is a carotenoid pigment extensively used in various industries. Rhodotorula sp. CP72-2, isolated from Calotropis gigantea, showed potential astaxanthin production. In this study, strain CP72-2 was identified as a putative new species in the genus Rhodotorula based on the 26S rRNA gene sequence (98% identity). It was first used as the microbial source for producing astaxanthin. Strain CP72-2 was screened for its astaxanthin production and was identified and quantified by High-Performance Liquid Chromatography (HPLC), Liquid Chromatography-Mass Spectrometry (LC-MS), and UV-Vis spectrophotometer. After a screening of astaxanthin production, various carbon sources, pH, temperature, and incubation period were evaluated for their effect on the astaxanthin production of strain CP72-2. Among the several experimental factors, the most efficient conditions for astaxanthin production were glucose (50 g/L), pH 4.5, 25 °C, and three days of cultivation. The assembly genome of strain CP72-2 has a total length of 21,358,924 bp and a GC content of 64.90%. The putative candidate astaxanthin biosynthesis-associated genes (i.e., CrtE, CrtYB, CrtI, CrtS, CrtR, CrtW, CrtO, and CrtZ) were found. This research presents the first report on the production and optimization of astaxanthin from strain CP72-2 and its genome analysis, focusing on the biotechnological potential of the astaxanthin producer

Diversity, astaxanthin production, and genomic analysis of Rhodotorula paludigena SP9-15

Astaxanthin is a carotenoid known for its powerful antioxidant properties. This study focused on isolating yeast strains capable of producing astaxanthin from flower and fruit samples collected in Thailand. Out of 115 isolates, 11 strains were identified that produced astaxanthin. Molecular identification techniques revealed that these isolates belonged to two species: Rhodotorula paludigena (5 isolates) and Rhodosporidiobolus ruineniae (6 isolates). Whole-genome analysis of one representative strain, R. paludigena SP9-15, identified putative candidate astaxanthin synthesis-associated genes, such as CrtE, CrtYB, CrtI, CrtS, CrtR, CrtW, CrtO, and CrtZ. High-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) confirmed astaxanthin production. Further optimization of astaxanthin production was carried out by investigating the effects of various factors on the growth rate and astaxanthin production. The optimal conditions were 40 g/L glucose as a carbon source, pH 7.5, and cultivation at 25 °C with 200 rpm for 3 days. Under these conditions, R. paludigena SP9-15 synthesized biomass of 11.771 ± 0.003 g/L, resulting in astaxanthin with a content of 0.558 ± 0.018 mg/g DCW (dry cell weight), an astaxanthin yield of 6.565 ± 0.238 mg/L, and astaxanthin productivity of 2.188 ± 0.069 g/L/day. These findings provide insights into astaxanthin production using red yeast strains from Thailand and highlight the potential of R. paludigena SP9-15 for further application

Efficient, Green, and Low-Cost Conversion of Bivalve-Shell Wastes to Value-Added Calcium Lactate

This work presents the efficient, green, and low-cost preparation of calcium lactate by using bivalve-shell wastes (cockle, mussel, and oyster shells) as raw materials. Three bivalve shells, a cockle, mussel, and oyster, were used separately as an alternative calcium-source material for the preparation of calcium lactate. The bivalve-shell waste was cleaned and milled, obtaining calcium carbonate (CaCO3) powder, which reacted to the lactic acid, forming calcium lactate. The effects of different calcium sources (cockle, mussel, and oyster) and different lactic acid concentrations (6, 8, and 10 mol/L) on the physicochemical properties of the synthesized calcium lactates were then investigated. The results pointed out that the highest solubility of the product was observed when 6 mol/L lactic acid and cockle-shell derived CaCO3 were employed for the calcium lactate preparation. The thermal decompositions of all calcium lactates occurred in three processes: dehydration, ethyl-lactate elimination, and decarbonization, respectively. The results, obtained from an infrared spectrometer, X-ray diffractometer, thermogravimetric analyzer, and scanning electron microscope, confirmed the formation of calcium lactate pentahydrate (Ca(CH3CHOHCOO)2·5H2O). The diffractograms also indicated the presence of two enantiomers of Ca(CH3CHOHCOO)2·5H2O, namely, of dl- and l-enantiomers, which depended on the lactic acid concentration used in the preparation process. The morphologies of calcium lactates show the firewood-like crystals in different microsizes, together with smaller irregular crystals. In summary, this work reports an effective process to prepare the valuable calcium lactates by using the cheap bivalve-shell-derived CaCO3 as a renewable calcium source