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Biocatalytic Upgrading of Opportunity Crudes
Published in Wael Ahmed Ismail, Jonathan Van Hamme, Hydrocarbon Biotechnology, 2023
Cytochrome c is a soluble hemeprotein, which catalyzes oxidation reactions on a number of hydrophobic compounds such as substituted phenols, organic sulfides, thiophenes, and PAHs. Cytochrome c has some advantages as a biocatalyst when compared with peroxidases for its application. It is stable in organic solvents, and even water-immiscible organic solvents, over a wide range of pH (2 to 11). Furthermore, Ryu et al. indicated economic advantages (Ryu et al., 2002). The catalytically interesting features of cytochrome c are centered in its heme active site (Figure 9.12). The functions of heme (iron-protoporphyrin IX) prosthetic groups in nature include a wide range of reactions such as electron transfer, oxygen transport and storage, catalysis, gas sensing, and gene regulation. The variable that defines the type of heme group is the nature of substituents on the porphyrin macrocycle. In the case of heme c, it is characterized by the presence of two covalent thioether bonds formed between Cys side chains and the heme vinyl groups at positions 2 and 4. The stereochemistry of heme attachment is the same in all known examples of heme c, and the vinyl groups at positions 2 and 4 are attached to the N- and C-terminal Cys of the CXXCH motif, respectively (Bowman and Bren, 2008).
Whether glycine betaine improves the thermotolerance of mesophilic anammox consortia
Published in Environmental Technology, 2020
Xiao-Ling Zhu, Yu-Hui Bai, Jing Wu, Lian-Zeng-Ji Xu, Ya-Fei Cheng, Nian-Si Fan, Ren-Cun Jin
According to the present working hypothesis, the anammox process is composed of three consecutive redox reactions: (1) nitrite is reduced to NO, (2) hydrazine is synthesized from ammonium and NO, and (3) hydrazine is oxidized to N2. Three heme proteins were identified at the main catalysts in this process: nitrite reductase (Nir), HZS and a variant of HAO [23]. Unlike other heme derivatives, heme c is covalently bound to its protein backbone and plays a very important role in electron-transfer and electron-storage, implying that heme c in the anammox biomass has a clear relationship with the anammox metabolism rate [38]. In this study, according to the analysis of heme c content, the amount of heme c showed a downward trend in both reactors. Throughout the experiment stages (Days 8–82), the heme c in T0 decreased by 51.8%, while in T1, heme c decreased by 59.6% with additions of 0.1, 1, and 2 mM GB. Furthermore, the SAA in T0 and T1 decreased significantly at 45°C (p < 0.05). The SAA in T1 decreased from 392.1 ± 12.1–6.0 ± 0.8 mg N g−1 VSS d−1. During the corresponding stages of GB addition (0.1, 1, and 2 mM), the SAA in T1 was not significantly higher than that in T0 (p > 0.05). Finally, according to the qPCR results, the number of copies of total bacteria and hzsA in T0 and T1 were negatively affected by high temperature, the relative abundances of total bacteria and hzsA had a significant decrease. Overall, the nitrogen removal capacity of the anammox reactors almost ceased, and the relative abundances of total bacteria and hzsA decreased at the higher temperature in both T0 and T1. In conclusion, the addition of GB did not improve the tolerance of an anammox biomass to high temperature.