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Biodegradation and Biocatalysis Aspects of Direct Bioethanol Production by Fungi in a Single Step Named Consolidated Bioprocessing
Published in Ayerim Y. Hernández Almanza, Nagamani Balagurusamy, Héctor Ruiz Leza, Cristóbal N. Aguilar, Bioethanol, 2023
Luis Fernando Amador Castro, Danay Carrillo Nieves
Versatile peroxidases (VPs) (EC 1.11.1.16) are ligninolytic heme peroxidases that are not only specific to Mn2+ as in the case of MnPs, but also can oxidase phenolic and non-phenolic substrates that are commonly employed by LiPs without the presence of manganese [56]. VPs have mainly been reported to be produced natively by fungi species of the genera Bjerkandera and Pleurotus [56, 57]. Similarly, to lignin and MnPs, multiple isoforms of VPs exists [58]. The molecular structure of VP possesses characteristics of both LiPs and MnP, however, it is more like LiP than MnP [59]. VPs have a mass around 37 kDa, an isoelectric point of ~3.5, and an acidic optimum pH of about 4.5 [60]. This type of peroxidases can oxidize substrates in a broad range of potentials, including low and high redox potentials compounds. The catalytic cycle of VP is like that of previously described lignin and manganese heme peroxidases. It involves the first two-electron oxidation followed by two reduction reactions in which intermediate compounds are formed to return the enzyme to its native oxidation state. The main difference is that these enzymes have the versatility of oxidizing either Mn2+ or other substrates to carry out their reduction reactions [59].
Manganese Particles in Freshwaters
Published in Jacques Buffle, Herman P. van Leeuwen, Environmental Particles, 2018
Richard R. De Vitre, William Davison
Although manganese particles are mainly present in freshwater as oxyhydroxides associated with bacteria, other particles often contain minor amounts of manganese. Typically 0.01% (range 0.001 to 0.1%) of the dry weight of phytoplankton is manganese,52,53 so for productive waters, with particulate organic carbon of 200 mmol/dm-3, only 5% of the observed particulate manganese of 0.2 mmol/dm-3 could be attributed to the organic material.54 Consequently, even in productive lakes, there is no apparent relationship between the concentrations of particulate organic carbon and particulate manganese,20,54 nor is manganese in material collected in sediment traps correlated with carbon.19 This settling flux of particulate Mn has been shown in several studies16,18,19,55 to be strongly influenced by redox cycling of the oxyhydroxides within the lake. Microprobe analysis of iron oxide particles which formed at a redox boundary in a lake showed them to contain 0.7 to 1.4% manganese,56 and iron sulfide particles isolated from the bottom waters of a lake were found to be up to 8% manganese.57 It is not known whether this manganese represents adsorbed Mn(II) or an association of manganese oxyhydroxides with the iron particles. Most minerals, including quartz and alumino silicates, can have a surface coating of oxidized iron and manganese.58,59
Critical Assemblies: Dragon Burst Assembly and Solution Assemblies
Published in Nuclear Technology, 2021
Robert Kimpland, Travis Grove, Peter Jaegers, Richard Malenfant, William Myers
Among the many noteworthy experiments performed with the water boiler was a manganese (Mn) foil irradiation experiment.33 A number of Mn foils were placed at various locations throughout the water boiler assembly and irradiated to map the flux as a function of radial position r. Manganese-55 absorbs a thermal neutron33 producing 56Mn that decays with a 2.8-h half-life and emits an 846.8-KeV gamma ray 99% of the time. The goal of this experiment was to provide data to compare with the predictions of diffusion34 and age theory.35 One interesting result was the determination of the equivalent untamped water boiler core. From diffusion theory, the water boiler experimenters expected the spatial distribution of the flux in an untamped spherical core to be expressed as follows: