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Development of Industrial Strain, Medium Characteristics and Biochemical Pathways
Published in Debabrata Das, Soumya Pandit, Industrial Biotechnology, 2021
The Entner–Doudoroff pathway (ED pathway) is a process similar to glycolysis that is active in bacterial systems. It involves the conversion of glucose to pyruvic acid through a phosphogluconate intermediate. The phosphogluconate is converted to KDPG, an important intermediate of the reaction. The yield is one molecule of pyruvate and 1 glyceraldehyde-3-phosphate (G3P). The G3P molecule follows the glycolysis pathway to form pyruvate. The site of the reaction is the cytoplasm of the cell. The net yield of the pathway is 1 ATP, 1 NADH and 1 NADPH from one glucose molecule. Distinct features of the Entner–Doudoroff pathway are that it occurs only in prokaryotes and it uses 6-phosphogluconate dehydratase and 2-keto-3-deoxyphosphogluconate aldolase to create pyruvate from glucose. These are the regulatory enzymes of the pathway which controls the progression of the reaction (Stafford and Stephanopoulos, 2001).
Medium Design for Cell Culture Processing
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Galactose and fructose do not get phosphorylated at their C6 position and enter the glycolysis pathway directly. They can serve as the main hexose source for cells through alternative entry points to glycolysis. Galactose is phosphorylated at C1 to become galactose 1-phosphate, and then through a transferase and an epimerase catalyzed reaction it becomes glucose 1-phosphate, which is converted to glucose 6-phosphate. Fructose, once in the cytosol, is converted to fructose 1-phosphate and split into dihydroxyacetone 3-phosphate and glyceraldehyde by aldolase. Both are then converted to glyceraldehyde 3-phosphate and enters glycolysis (Figure 7.4).
Glycolysis and Fermentation
Published in Jean-Louis Burgot, Thermodynamics in Bioenergetics, 2019
Fructose and galactose can enter into the glycolytic chain. fructose enters into glycolytic chain through the formation of fructose-1-phosphate with the aid of fructokinase. Then, the fructose-1-phosphate is cut into two parts: the glyceraldehyde plus the dihydroxyacetonephosphate. Here, again, there is a cleavage by retroaldolisation catalysed by a specific fructose-1-phosphate aldolase. The glyceraldehyde is then phosphorylated in glyceraldehyde-3-phosphate by a triose kinase. Hence, it can enter into the glycolysis: galactose enters through the glycolysis chain once it is transformed into glucose-6-phosphate by a process in four steps. There is first the transformation galactose → galactose-1-phosphate: galactose + ATP→galactokinasegalactose-1-phosphate + ADP + H+Secondly, the galactose-1-phosphate reacts with the uridine diphospho-glucose (UDP-glucose) and gives the UDP-galactose and the glucose-1-phosphate. The reaction is catalyzed by the galactose-1-phosphate uridyl transferase. Transformation of galactose-1-phosphate into glucose-1-phosphate.
Insights into the microbiomes for medium-chain carboxylic acids production from biowastes through chain elongation
Published in Critical Reviews in Environmental Science and Technology, 2022
Xingdong Shi, Lan Wu, Wei Wei, Bing-Jie Ni
Generally, pyruvate plays an important intermediate in generating various primary fermentation products (Figure 1). The conversion of glucose or other carbohydrate to pyruvate is the central ATP synthesis pathway, which includes Embdem-Meyerhof-Parnas (EMP), Entner-Doudoroff (ED) glycolysis and pentose-phosphate pathway (PPP) (Figure 1A) (de Vrije et al., 2007; Garrett & Grisham, 2017). EMP is more efficient in forming ATP than ED and PPP (Hoelzle et al., 2014). In EMP glycolysis, 1 mol glucose are initially oxidized to 2 mol glyceraldehyde-3-phosphate (G3P) which are then transformed to 2 mol pyruvate, liberating 2 mol ATP simultaneously. Produced pyruvate would be further converted to various SCCAs during primary fermentation (Figure 1B–E). Table S2 summarizes the fermentation processes of pyruvate and its typical dominant microorganisms. These processes are widely present in the mixed-culture reactor because its products, SCCAs, are the precursors of CE.
Enhancing the production of poly-γ-glutamate in Bacillus subtilis ZJS18 by the heat- and osmotic shock and its mechanism
Published in Preparative Biochemistry & Biotechnology, 2020
Yichao Song, Yishu Zhang, Min He, Hang Liu, Chunyu Hu, Liuzhen Yang, Ping Yu
As shown in Figure 3a, the activity of glucose-6-phosphate dehydrogenase under all three conditions was decreased with the fermentation time prolonged, indicating that the concentrations of the carbon sources and other nutrients decreased as the cells grew. This also made the concentration of enzyme-catalyzed substrate decreased, resulting in reducing the activity of enzyme. Glucose-6-phosphate dehydrogenase first participates in the pentose phosphate pathway in the endogenous glutamate metabolism. Its role is to catalyze the conversion of 6-phosphoglucose to 6-phosphogluconate. Glyceraldehyde-3-phosphate and fructose-6-phosphate are generated in the pentose phosphate pathway, and reentered the glycolysis pathway [24]. The activity of glucose-6-phosphate dehydrogenase was the highest under unshocked condition compared to the other two shock conditions (Figure 3a), which increased the metabolic rate of the pentose phosphate pathway and resulted in loss of carbon sources toward the biosynthesis of γ-PGA. Thus, it was speculated that heat- and osmotic shock could improve the biosynthesis of γ-PGA by decreasing the activity of glucose-6-phosphate dehydrogenase.