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1. The Effect of Dicarboxylic Acid Catalyst Structure on Hydrolysis of CelluloseModel Compound D-Cellobiose in Water

   https://doi.org/10.2174/2213337208666211129090444  

   Fernando, Harshica; Amarasekara, Ananda S. (June 2022, Current Organocatalysis)

   Background:Polycarboxylic acids are of interest as simple mimics for cellulase enzyme catalyzed depolymerization of cellulose. In this study, DFT calculations were used to investigate the effect of structure on dicarboxylic acid organo-catalyzed hydrolysis of cellulose model compound D-cellobiose to D-glucose. Methods:Binding energy of the complex formed between D-cellobiose and acid (Ebind), as well as glycosidic oxygen to dicarboxylic acid closest acidic H distance were studied as key parameters affecting the turn over frequency of hydrolysis in water. Result:α-D-cellobiose - dicarboxylic acid catalyst down face approach showed high Ebind values for five of the six acids studied; indicating the favorability of down face approach. Maleic, cis-1,2-cyclohexane dicarboxylic, and phthalic acids with the highest catalytic activities showed glycosidic oxygen to dicarboxylic acid acidic H distances 3.5-3.6 Å in the preferred configuration. Conclusion:The high catalytic activities of these acids may be due to the rigid structure, where acid groups are held in a fixed geometry. 

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2. Post‐secretory synthesis of a natural analog of iron‐gall ink in the black nectar of Melianthus spp.

   https://doi.org/10.1111/nph.18859  

   Magner, Evin T.; Roy, Rahul; Freund Saxhaug, Katrina; Zambre, Amod; Bruns, Kaitlyn; Snell‐Rood, Emilie C.; Hampton, Marshall; Hegeman, Adrian D.; Carter, Clay J. (March 2023, New Phytologist)

   Summary The black nectar produced byMelianthusflowers is thought to serve as a visual attractant to bird pollinators, but the chemical identity and synthesis of the black pigment are unknown.A combination of analytical biochemistry, transcriptomics, proteomics, and enzyme assays was used to identify the pigment that givesMelianthusnectar its black color and how it is synthesized. Visual modeling of pollinators was also used to infer a potential function of the black coloration.High concentrations of ellagic acid and iron give the nectar its dark black color, which can be recapitulated through synthetic solutions containing only ellagic acid and iron(iii). The nectar also contains a peroxidase that oxidizes gallic acid to form ellagic acid.In vitroreactions containing the nectar peroxidase, gallic acid, hydrogen peroxide, and iron(iii) fully recreate the black color of the nectar. Visual modeling indicates that the black color is highly conspicuous to avian pollinators within the context of the flower.Melianthusnectar contains a natural analog of iron‐gall ink, which humans have used since at least medieval times. This pigment is derived from an ellagic acid‐Fe complex synthesized in the nectar and is likely involved in the attraction of passerine pollinators endemic to southern Africa. 

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3. Biologically Available Phosphorus in Biocrust-Dominated Soils of the Chihuahuan Desert

   https://doi.org/10.3390/soilsystems2040056  

   Crain, Grace; McLaren, Jennie; Brunner, Benjamin; Darrouzet-Nardi, Anthony (December 2018, Soil Systems)

   In desert soils, phosphorus (P) cycling is controlled by both geochemical and biological factors and remains less studied than nitrogen and carbon. We examined these P cycling factors in the context of biological soil crusts (biocrusts), which are important drivers of nutrient cycling in drylands and have the potential to release bound labile P. We adopted the biologically-based P (BBP) method, which allows examination of biologically relevant P fractions. The BBP method incorporates four extractions: dilute calcium chloride (CaCl2), citric acid, phosphatase enzymes, and hydrochloric acid (HCl). We coupled the extractions with a 33P-labeled orthophosphate addition and incubation to assess the fate of freshly available phosphate (PO43−). Low P concentrations in the dilute CaCl2 extractions suggest that drylands lack accessible P in the soil solution, while higher amounts in the citric acid- and enzyme-extractable pools suggest that dryland microbes may acquire P through the release of organic acids and phosphatases. The addition of 33PO43− was, within 24 h, quickly adsorbed onto mineral surfaces or incorporated into hydrolysable organic compounds. Areas with biocrusts showed overall lower P concentrations across all four extractable pools. This suggests that biocrust organisms may prevent P adsorption onto mineral surfaces by incorporating P into their biomass. Overall, our results indicate that organisms may have to employ several viable strategies, including organic acid and enzyme production, to access P in dryland soils. 

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4. Kinetic modeling of anaerobic degradation of plant-derived aromatic mixtures by Rhodopseudomonas palustris

   https://doi.org/10.1007/s10532-021-09932-3  

   Ma, Yanjun; Donohue, Timothy J.; Noguera, Daniel R. (April 2021, Biodegradation)

   null (Ed.)

   Abstract Rhodopseudomonas palustris is a model microorganism for studying the anaerobic metabolism of aromatic compounds. While it is well documented which aromatics can serve as sole organic carbon sources, co-metabolism of other aromatics is poorly understood. This study used kinetic modeling to analyze the simultaneous degradation of aromatic compounds present in corn stover hydrolysates and model the co-metabolism of aromatics not known to support growth of R. palustris as sole organic substrates. The simulation predicted that p -coumaroyl amide and feruloyl amide were hydrolyzed to p -coumaric acid and ferulic acid, respectively, and further transformed via p -coumaroyl-CoA and feruloyl-CoA. The modeling also suggested that metabolism of p -hydroxyphenyl aromatics was slowed by substrate inhibition, whereas the transformation of guaiacyl aromatics was inhibited by their p -hydroxyphenyl counterparts. It also predicted that substrate channeling may occur during degradation of p -coumaroyl-CoA and feruloyl-CoA, resulting in no detectable accumulation of p -hydroxybenzaldehyde and vanillin, during the transformation of these CoA ligated compounds to p- hydroxybenzoic acid and vanillic acid, respectively. While the simulation correctly represented the known transformation of p -hydroxybenzoic acid via the benzoyl-CoA pathway, it also suggested co-metabolism of vanillic acid and syringic acid, which are known not to serve as photoheterotrophic growth substrate for R. palustris . 

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5. Effect of Lead in Antimony and Tin Dissolution from Recycled Lead–Acid Battery Dross in Hydrobromic Acid Solution

   https://doi.org/10.3390/met15040356  

   Hirata-Miyasaki, Arturo; Anderson, Corby G (April 2025, Metals)

   Bertruol, Daniel (Ed.)

   Demand and prices for antimony have increased over the last few years. Recycling supplied 15% of domestic consumption in the US, while the remaining 85% was imported. Hydrometallurgical processes have long used alkaline sulfide systems and hydrochloric acid, closing doors on new approaches. Bromine compounds have been recently used to recover PGMs and REEs successfully; thus, antimony leaching with bromine compounds is theoretically feasible. This research was conducted to develop a viable technology for hydrobromic acid between 50 °C and 70 °C as a leaching reagent on dross through single- and two-stage leaching using design of experiment (DoE) and adding sustainability to current industrial processes while minimizing waste products in recycling processes. The preliminary results showed that bromine, specifically hydrobromic acid, can be used as a leaching reagent for antimony dissolution. By decreasing the lead content in the solids and increasing the concentration, temperature, and reaction time, antimony leaching from the dross was increased from 20% to 50%. The findings, coupled with acid regeneration, can be implemented as an alternative to other reagents in industrial plants. 

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