Characterization of CcMANS1, a putative Mannan synthase from \u3ci\u3eCoffea canephora\u3c/i\u3e

Mannans are a type of hemicellulosic plant cell wall polysaccharide that offer structural support and serve as energy reserves for developing plants. Coffee seeds are rich in mannans, and mannan content of coffee seeds impacts brew quality. Mannan backbones are synthesized by CSLA proteins. This study aims to characterize a CSLA enzyme from Coffea canephora (mannan synthase 1; CcMANS1) that has been implicated in the biosynthesis of backbones of coffee seed mannans. This enzyme has not been biochemically characterized and characterizing its activity will help contribute to an understanding of the differences between CSLA proteins that dictate the composition of carbohydrate products. Recombinant CcMANS1 was produced using transgenic Pichia pastoris and Saccharomyces cerevisiae. Despite the use of multiple assays, including biochemical assays, fluorophore assisted carbohydrate electrophoresis, and mass spectroscopy, it was not possible to confirm mannan synthase activity of recombinant CcMANS1. Future studies that characterize additional putative mannan synthases or that focus on identifying the cause(s) of inactivity of CcMANS1 may prove beneficial

Comprehensive examination of acid leaching behaviour of mineral phases from red mud: Recovery of Fe, Al, Ti, and Si

Red mud represents an environmental and economic liability for the alumina industry in the form of wasted raw material. Although some leaching studies have been performed, there are deficiencies in the current literature regarding the amounts of metals extracted relative to each other, and minimal information regarding silicon contamination of extracts. There is also limited knowledge of extraction efficiencies of different acids (particularly in the case of phosphoric acid) under the same experimental conditions. This study focused on the leaching behaviour of the four most extractable elements present within red mud (iron, titanium, aluminium and silicon). By varying the experimental conditions, acid concentration, and type of acid, a comprehensive dataset of leaching trends was obtained. This allowed for direct comparison of leaching efficiency for the four elements under the same conditions, which was difficult previously due to the variation of experimental conditions and red mud composition between studies. The patterns in recoveries were explained in terms of the reactivities of the mineral phases within red mud and the interaction between the different acids and the reaction surfaces. Out of the four acids studied (nitric, hydrochloric, sulfuric, and phosphoric) phosphoric and hydrochloric acids produced some of the best recoveries for iron (76–78%) and titanium (23–24%), and phosphoric acid also produced the highest recoveries for silicon (49%) and aluminium (50%). The differences observed between the acid types and reaction conditions revealed potential for development of element selective extraction methods.\ud Additionally, explaining leaching behaviour in terms of the mineral phases present allowed easier prediction of expected leaching trends for these four elements, which made this study applicable to red muds with a wide variety of compositions

Vibrational spectroscopy of the multianion mineral Kemmlitzite (Sr,Ce)Al3(AsO4)(SO4)(OH)6

Some minerals are colloidal and show no X-ray diffraction patterns. Vibrational spectroscopy offers one of the few methods for the assessment of the structure of these types of mineral. Among this group of minerals is kemmlitzite (Sr,Ce)Al3(AsO4)(SO4)(OH)6. The objective of this research is to determine the molecular structure of the mineral kemmlitzite using vibrational spectroscopy. Raman microscopy offers a useful method for the analysis of such colloidal minerals. Raman and infrared bands are attributed to the AsO43- , SO42- and water stretching vibrations. The Raman spectrum is dominated by a very intense sharp band at 984 cm-1 assigned to the SO42- symmetric stretching mode. Raman bands at 690, 772 and 825 cm-1 may be assigned to the AsO43- antisymmetric and symmetric stretching modes. Raman bands observed at 432 and 465 cm-1 are attributable to the doubly degenerate 2 (SO4)2- bending mode. Vibrational spectroscopy is important in the assessment of the molecular structure of the kemmlitzite, especially when the mineral is non-diffracting or poorly diffracting

Weathering behaviour of bauxite residue with pH: Experimental and geochemical modelling

This study attempted to predict the weathering behaviour of bauxite residue, which is of primary concern to understanding the environmental risks of leachates from the ever-growing quantity of reserves. Leaching experiments for bauxite residue were carried out with deionised water at various solution pHs between 5-13. A model with no adjustable parameters was developed using PHREEQC with the XRD mineralogical composition being used as direct inputs to the model. Acid neutralisation curves obtained experimentally compared favourably with PHREEQC modelling results over the entire pH range. Sodalite (7.5-5.7) and calcite (8.0-5.5) were found to be critical buffering minerals during weathering of bauxite residue. Leaching experiments showed that Na, Al, V and, to some extent Ca, posed a threat to the environment as their concentrations in the leachate exceeded permissible limits outlined by WHO. The PHREEQC model was validated by the experimental trends for Na, Ca and Al. The pH was found to strongly influence the distribution of the species of different elements in the leachate. Above a pH of 6.5, Al(OH) was the dominant Al species; HCO dominated up to a pH of 9.0 before CO became the dominant C species. HSiO was found to be the dominant Si species before HSiO - became prominent at pH > 10 and HSiO at pH > 12.5. The kinetics of the weathering process at solution pH 8.35, 9.23, 10.12 and 11.06 showed first order chemical reaction resistance to be rate-controlling