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2-Capture and Conversion Technologies
Published in Ashok Kumar, Swati Sharma, 2 Utilization, 2020
Tanvi Sharma, Abhishek Sharma, Swati Sharma, Anand Giri, Ashok Kumar, Deepak Pant
Carbon monoxide (CO) is considered as waste gas, yet it is a vital feedstock for the synthesis of many fuels and chemicals. Mostly, the conversion of CO2 to CO occurs in the presence of a catalyst, which results in a decrease in reaction rate and an increase in reaction velocity. Recently, the rhenium tricarbonyl catalyst attracted the attention of researchers for the conversion of CO2 to CO. Carbon monoxide dehydrogenase from Moorella thermoacetica was the first reported biological catalyst for the electrochemical reduction of CO2, and it exhibits no overpotential. However, the direct electrochemical reduction of CO2 requires 1–2-V overpotential. Carbon monoxide dehydrogenase is another important metalloenzyme that contains nickel and iron in its inactive site, which catalyses the reversible oxidation of CO to CO2. Several metal-centred catalysts such as nickel, iron, cobalt, and ruthenium catalyse the conversion of CO2 into a value-added product (Agarwal et al. 2012; Shin et al. 2003). Further insights in this field are required to develop an effective catalytic system in terms of selectivity and overpotential.
Effects of Fe3O4 nanoparticles on anaerobic digestion enzymes and microbial community of sludge
Published in Environmental Technology, 2023
Jun Zhou, Haonan Zhang, Jianbo Liu, Lei Gong, Xiaoqi Yang, Tong Zuo, Ying Zhou, Jin Wang, Xiaogang You, Qinwei Jia, Luyu Wang
Yang et al. [18] found that there was a linear relationship between cumulative biogas production and protein degradation, and protease plays a vital role in protein degradation. Wang et al. [19] found that cellulase pretreatment could improve the hydrolysis process of cellulose by reducing the crystallinity of cellulose and promoting methane production. Parawira et al. [20] found that with the enhancement of amylase, when there is a large amount of starch in the substrate, the formation rate of reducing sugar and oligosaccharide is accelerated, which was beneficial to the role of acetic acid-producing bacteria. The acidification process is the preparatory stage of the methanogenic process, in which many enzymes such as dehydrogenase and acetate kinase (AK) were involved [21]. As an oxidoreductase, dehydrogenase can activate hydrogen ions in organic compounds and transfer them to specific receptors [22]. Tao et al. [23] found that a low voltage electric field can promote the relative activity of functional enzymes such as acetate kinase, thus promoting the effect of hydrogen production by anaerobic fermentation. The process of methanogenesis requires the joint action of a variety of enzymes and coenzymes, such as carbon monoxide dehydrogenase, acetyl coenzyme, coenzyme F420 etc. [24]. Tian et al. [25] found that the addition of nano-graphene could significantly increase the content of coenzyme F420 in anaerobic digestion and accelerate the conversion of acetic acid to methane.
Optimization of cobalt, nickel, and iron supplement for mesophilic and thermophilic anaerobic digestion treating high-solid food waste
Published in Environmental Technology, 2022
Trace metals that are considered the most essential in AD are transition metals, e.g. cobalt (Co), nickel (Ni), and iron (Fe) [10]. Co is a core trace metal of vitamin B12 and is involved in methyltransferase activity required for methyl group transfer from methanol-containing compounds in methanogenesis [6, 11]. Ni is a key component of carbon monoxide dehydrogenase and in cofactor F430 in methyl-coenzyme M reductase [6]. Ni addition has been extremely important for increasing uptake of volatile fatty acids (VFAs) and production of biogas [6]. CH4-forming bacteria and anaerobic digesters have often been reported to require Ni [12]. Fe supplementation can increase acetate utilization by methanogens and promote conversion of CO2 to CH4 [13, 14]. However, excessive trace metal concentrations cause inhibition of methanogenesis [8].
Lemna minor, a hyperaccumulator shows elevated levels of Cd accumulation and genomic template stability in binary application of Cd and Ni: a physiological and genetic approach
Published in International Journal of Phytoremediation, 2021
Ibrahim Ilker Ozyigit, Lutfi Arda, Bestenur Yalcin, Ibrahim Ertugrul Yalcin, Bihter Ucar, Asli Hocaoglu-Ozyigit
Among the heavy metals, Cd is shown as having comparatively highest toxic effects while Ni is identified as being essential/beneficial, especially in low concentrations and therefore, considered as an essential nutrient required in small quantities (25–35 µg/day for human and 0.05–5 μg g−1 dry weight for plants) (Jan et al.2015; Karahan et al.2020). Ni acts as cofactor in several enzymes including urease, hydrogenase, carbon monoxide dehydrogenase and other Ni-containing enzymes (Doganlar et al.2012). Chovancová et al. (2011) reported that Ni application has significant beneficial effects on the microscopic structure and thickness of the cortical bone in rats. The presence of Ni in low levels significantly improves plant growth and root development in great extents by the effects of enzyme activations (Andreeva et al.2001; Da silva et al.2012).