China
Africa
Explore chapters and articles related to this topic
Syngas as a Sustainable Carbon Source for PHA Production
Published in Martin Koller, The Handbook of Polyhydroxyalkanoates, 2020
Véronique Amstutz, Manfred Zinn
Acetate is produced from acetyl-CoA via an acetyl-phosphate intermediate on the basis of catalysis by phosphotransacetylase and acetate kinase as the first and the second step, respectively. This second enzyme involves substrate-level phosphorylation and therefore yields an ATP molecule, the source of energy in the bacteria. This conversion is thus expected to be growth related [63]. In autotrophic conditions (H2 + CO2), cultures of Acetobacterium woodii and two genetically modified strains for overexpression of WL pathway enzymes in a continuous stirred tank reactor (CSTR) yielded 8.2–9.6 g/L acetate, with a specific production rate of 20.5–21.8 g g–1 d–1 [64]. A yield of 44 g/L (0.8 M) of acetate could be obtained with a maximum specific production rate of 6.9 g g–1 d–1 using the same microorganism and a CO2 and H2 substrate [65].
Biological Process for Butanol Production
Published in Jay J. Cheng, Biomass to Renewable Energy Processes, 2017
Maurycy Daroch, Jian-Hang Zhu, Fangxiao Yang
Acidogenesis starts in two major branch points of the metabolism acetyl-CoA and butyryl-CoA. During the acid-producing phase, acetate and butyrate are produced from acetyl-CoA and butyryl-CoA with two analogous, yet distinct sets of enzymes. Formation of acetate from acetyl-CoA is a two-step reaction catalyzed by phosphate acetyltransferase (phosphotransacetylase) and acetate kinase. The first of the two reactions yields acetyl phosphate from acetyl-CoA; the second one dephosphorylates acetyl phosphate to acetate yielding ATP as the second product. Analogously, formation of butyrate from butyrate-CoA follows the same pattern catalyzed by phosphate butyryltransferase (phosphotransbutyrylase) and butyryl kinase. Reaction catalyzed by phosphate butyryltransferase yields butyryl phosphate, while subsequent dephosphorylation reaction yields butyrate and ATP. Although in principle C. acetobutylicum can also convert pyruvate to lactate under certain conditions, this reaction is not considered an acidogenic reaction as this pathway is not operational under normal conditions (Jones and Woods, 1986). The two main sets of reactions originating from acetyl- and butyryl-CoA are important sources of ATP for the metabolism, but yield in the formation of highly acidic byproducts (acetate, butyrate) that in high concentrations of fermentation become toxic to the cells and induce metabolic shift from acidogenesis to solvengenesis.
Dark Fermentative Hydrogen Production:
Published in Farshad Darvishi Harzevili, Serge Hiligsmann, Microbial Fuels, 2017
Patrícia Madeira da Silva Moura, Joana Resende Ortigueira, Idania Valdez-Vazquez, Ganesh Dattatray Saratale, Rijuta Ganesh Saratale, Carla Alexandra Monteiro da Silva
In the acetate and butyrate fermentation, acetyl-CoA is an important metabolic intermediate, constituting a branching point for acetate and butyrate formation pathways (Liu et al., 2006). In the acetate pathway, acetyl-CoA and 2 mol H2/mol glucose are produced from the phosphoroclastic reaction catalyzed by Pfor from pyruvate oxidation. Acetate production from acetyl-CoA is then catalyzed by phosphotransacetylase (Pta) and acetate kinase (Ack), with the intermediate formation of acetyl-phosphate and two additional moles of ATP (Liu et al., 2006; Zhang et al., 2009). In this pathway, however, more H2 is evolved than is pyruvate oxidized (Thauer et al., 1977). When the H2 partial pressure is low, hydrogenase oxidizes reduced ferredoxin, producing H2. This increases the Fd/FdH2 ratio, and Nfor couples NADH oxidation to ferredoxin reduction (Kim and Gadd, 2008). Acetyl-CoA is no longer needed as the electron acceptor for NADH reoxidation, and it is converted to acetyl-phosphate and further to acetate and ATP. Since 2 mol NADH are generated during glycolysis, a maximum of two additional moles of H2 can be produced per mole of glucose (Hallenbeck and Ghosh, 2009). Hence, obligate anaerobes are theoretically able to produce a maximum of 4 mol H2/mol glucose consumed, with reductant provided by 2 mol NADH and 4 mol reduced Fd, when glucose is catabolized solely to acetate (Schut and Adams, 2009) (Equation 7.9).
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.
Effect of Fe3O4 nanoparticles on the performance of anaerobic digestion through electrochemical analysis
Published in Environmental Technology, 2022
Lei Gong, Tong Zuo, Yi Qian, Jianbo Liu, Jun Zhou, Haonan Zhang, Jin Wang, Ying Zhou, Xiaoqi Yang, Luyu Wang, Qinwei Jia
The enzyme electrodes were put into the propionic acid electrolyte to explore the activity of acetate kinase. Acetic acid kinase decomposes propionic acid into acetic acid for methanogens to use. Figure 6(a) showed that the enzyme electrode of the group of 200 mg/L Fe3O4 NPs produced the highest quantity of electric charge was 0.006 mC. At this time, the electrochemically active area was the largest, and the activity of acetate kinase was the highest. After 8 days, the quantity of electric charge produced by all the groups began to increase, the activity of acetate kinase was enhanced, and propionic acid was decomposed to the greatest extent. As the AD time increased, the quantity of electric charge produced by each group gradually decreased, and then the activity of acetate kinase also decreased.
Effect of sodium dodecyl benzene sulfonate (SDBS) on the performance of anaerobic co-digestion with sewage sludge, food waste, and green waste
Published in Chemical Engineering Communications, 2020
Xiaofang Pan, Jian Sun, Youchi Zhang, Gefu Zhu
The enzymes for hydrolysis (acidic protease, neutral protease, alkaline protease, and α-glucosidase), acetogenesis (acetate kinase), methanogenesis (coenzyme F420), and the activity of microorganisms (dehydrogenase) were examined in this study. As shown in Table 2, the presence of SDBS improved the activities of hydrolytic enzymes either for protease or α-glucosidase. Furthermore, in the treatment with 0.05 g/g SDBS, the activity of neutral protease, acid protease, and α-glucosidase were higher than other treatments. For acetate kinase, dehydrogenase, and coenzyme F420, the presence of SDBS decreased the activity of either enzyme. For instance, in the treatment with 0.2 g/g SDBS, the activity of dehydrogenase, acetate kinase, and coenzyme F420 were decreased by 55%, 85%, and 49%. The presence of SDBS would affect the growth and activities of microorganisms, resulting in the variation of enzymes activities.