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Biohydrogen
Published in Ozcan Konur, Bioenergy and Biofuels, 2017
For any fermentative process, supplementation of suitable metal ions in media is essential. These metal ions act as enzyme cofactors and are also involved in the cellular transport processes. Hydrogenase, the key enzyme involved in hydrogen production, contains a bimetallic Fe-Fe center. It is also surrounded by FeS protein clusters (Nicolet et al., 2002). Therefore, several researchers have studied the effect of supplementation of iron on biohydrogen production. For example, Lee et al. (2001) studied the effect of iron concentration on hydrogen fermentation and found that higher Fe-ion concentration influences the system. The maximum rate of hydrogen production of 24 mL/g volatile suspended solids (VSS) h was obtained when the media were supplemented with 4,000 mg/L FeCl2 (Lee et al., 2001). In addition, during the glycolysis process, the magnesium ion acts as an important cofactor for 10 different enzymes, including hexokinase, phosphofructokinase, and phosphoglycerate kinase. Lin and Lay (2004) also studied the effect of various trace elements (Mg, Na, Zn, Fe, K, I, Co, Mn, Ni, Cu, Mo, and Ca) on hydrogen production using Cl. pasteurianum. The study showed that suitable concentrations of Mg, Na, Zn, and Fe were necessary for a higher hydrogen yield (Lin and Lay, 2004).
Biochemistry
Published in Ronald Fayer, Lihua Xiao, Cryptosporidium and Cryptosporidiosis, 2007
Because of the lack of a Krebs cycle, Cryptosporidium may rely solely on glycolysis as its energy source. It can utilize polysaccharides, including amylopectin, amylose, and hexoses such as glucose and fructose (Figure 3.1). All enzymes catalyzing reactions from hexose to pyruvate are present in the genome, in which hexokinase (HK) consumes one ATP in activating hexose, whereas phosphoglycerate kinase (PGK) and pyruvate kinase (PK) may each produce two ATPs when a single hexose is completely converted into two pyruvate molecules. Unlike humans or other typical aerobic organisms that use an ATP-dependent phosphofructokinase (ATP-PFK), but similar to some other microanaerobic protists including Trichomonas and Giardia, Cryptosporidium uses a pyrophosphate-dependent PFK (PPi-PFK) to economize ATP consumption, for which the activity was previously detected in oocysts (Denton et al., 1996). Because Cryptosporidium does not have a Krebs cycle to completely oxidize carbohydrates, this parasite can generate only 3 net ATP molecules from a single hexose, which is much fewer than those generated by the aerobic pathway (up to 36 ATPs), but significantly higher than typical glycolysis that uses ATP-PFK (only 2 net ATPs). Phosphoenolpyruvate (PEP) may be directly converted to pyruvate by PK, or indirectly via PEP carboxylase (PEPCL), malate dehydrogenase (MDH), and malic enzyme (ME). Although a weak activity of glycerol kinase (GK) catalyzing the formation of glycerol from glycerol-3P was previously reported in oocyst extracts (Entrala and Mascaro, 1997), its gene ortholog cannot be found in either the C. parvum or C. hominis genome, suggesting that glycerol is not one of the end products for generating another ATP as seen in some other protists including trypanosomes (Kralova et al., 2000). However, Cryptosporidium is able to use glycerol-3P to synthesize phospholipid or other complex lipids.
Biological Process for Ethanol Production
Published in Jay J. Cheng, Biomass to Renewable Energy Processes, 2017
Under the catalysis of phosphoglycerate kinase assisted by Mg2+ and the presence of ADP, 1,3-diphosphoglycerate transfers a high energy phosphorus to ADP to form 3-phosphoglycerate.
Modeling and simulation of single droplet drying in an acoustic levitator
Published in Drying Technology, 2023
Martin Doß, Nadja Ray, Eberhard Bänsch
As an essential enzyme for glycolysis, phosphoglycerate kinase (PGK) can be found in all living organisms. Inside the cells, it catalyzes the production of adenosine triphosphate (ATP) and thus energy from sugar. Having too little or too much PGK within the human body promotes diseases like hemolytic anemia or gastric cancer.[54,55] Compared to other proteins, PGK is rather small counting only 416 amino acids in its polypeptide chain. Therefore, and due to its pharmaceutical relevance, PGK is chosen as a representative model protein for our single droplet drying study.