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Glycolysis and Fermentation
Published in Jean-Louis Burgot, Thermodynamics in Bioenergetics, 2019
In the second step, the glucose-6-phosphate is transformed into the fructose-6-phosphate II’: glucose-6-phosphate→phosphohexoseisomerasefructose-6-phosphateII’
Biological Process for Ethanol Production
Published in Jay J. Cheng, Biomass to Renewable Energy Processes, 2017
Under the catalysis of phosphoglucose isomerase, glucose-6-phosphate is isomerized to fructose-6-phosphate. This is a reversible reaction and the ratio of glucose-6-phosphate to fructose-6-phosphate is normally 7:3 at equilibrium. However, the reaction rate is very high.
Chitosan production by Penicillium citrinum using paper mill wastewater and rice straw hydrolysate as low-cost substrates in a continuous stirred tank reactor
Published in Environmental Technology, 2023
M.M.T. Namboodiri, Arul Manikandan, Tanushree Paul, Kannan Pakshirajan, G. Pugazhenthi
The effect of adding acetic acid at initial concentrations of 20, 50, 80, 100 and 150 mg L−1 to the paper mill wastewater supplemented with MSM revealed that 50 mg L−1 acetic acid is optimum for achieving a maximum COD removal of 67% and chitosan yield of 13.7% DCW. The enhancement in chitosan yield and COD removal from paper mill wastewater by P. citrinum due to acetic acid addition can be explained as follows. Paper and pulp wastewater contain cellulose, xylose and hemicellulose residues in low amounts along with the polymers lignin and phenolics. The high values of XR and XDH activity in the presence of acetic acid at low concentrations in this study suggest efficient utilization of xylose present in the wastewater, which subsequently enhanced the fungal growth. Xylose is first converted to xylulose by xylose reductase (XR), then converted to xylitol by xylitol dehydrogenase (XDH). Fructose 6-phosphate formed from xylitol acts as an important intermediate in hemicellulose utilization pathways, including accumulation of chitin and chitosan by fungi. The activities of XR and XDH were also high in the presence of acetic acid at low concentrations [18]. Other than acetic acid, compounds such as formic acid and furfurals at low concentrations in the media, enhance chitosan production by fungi.
Comparative proteomic analysis revealed the metabolic mechanism of excessive exopolysaccharide synthesis by Bacillus mucilaginosus under CaCO3 addition
Published in Preparative Biochemistry & Biotechnology, 2019
Hongyu Xu, Zhiwen Zhang, Hui Li, Yujie Yan, Jinsong Shi, Zhenghong Xu
Glucose-6-phosphate isomerase (Pgi), a second glycolytic enzyme, catalyzed the reversible aldose–ketose isomerization of glucose-6-phosphate to fructose 6-phosphate. This enzyme is also an enzymatic link between glycolysis and the pentose phosphate pathway.[27] 6-Phosphofructokinase (PfkA) was believed to be the most important element for the control of glycolytic flux. This enzyme catalyzes a physiologically reversible interconversion of fructose-6-phosphate and fructose-1,6-bisphosphate.[28] Aconitate hydratase (Acn), which transforms citrate to isocitrate, was the first step of the TCA cycle.[29] Glucose-6-phosphate dehydrogenase (G6PD) directed glucose-6-phosphate into the pentose phosphate pathway and played a pivotal role in cell function.[30] In this study, we found that all the four enzymes were down-regulated with CaCO3 addition and created a decreased carbon flux toward the growth of cells.
Reactor and microreactor performance and kinetics of the aldol addition of dihydroxyacetone to benzyloxycarbonyl-N-3-aminopropanal catalyzed by D-fructose-6-phosphate aldolase variant A129G
Published in Chemical Engineering Communications, 2019
Martina Sudar, Zvjezdana Findrik, Anna Szekrenyi, Pere Clapés, Đurđa Vasić-Rački
D-Fructose-6-phosphate aldolase variant, FSA A129G (Szekrenyi et al., 2014), was investigated for the aldol addition of 2 to 1. Preliminary experiments showed (data not reported) that this variant improved the reaction performance for this aldol addition reaction, although, unexpectedly it increased also the activity and reaction performance for glycolaldehyde additions (Szekrenyi et al., 2014). The influence of pH (7.0–8.6) on enzyme activity was investigated. The results showed a typical bell-like dependence (Figure 1). The highest enzyme activity was obtained in 50 mmol dm−3 TEA HCl buffer pH 7.5. These conditions were further used for kinetic measurements and other experiments. Since 1 has limited solubility in water, the presence of an organic co-solvent in the reaction media was needed. Hence, the effect of co-solvent, ethyl acetate or acetonitrile, on FSA A129G activity was evaluated in the range of 5–50% v/v (Figure 2). Increasing the concentration of co-solvent caused a significant decrease of enzyme activity and thus only lower concentration (5 and 10% v/v) were used in all further experiments to assure the balance between maximum enzyme activity and solubility of 1. The highest enzyme activity was obtained in ethyl acetate (Figure 2), which was used for all kinetic measurements and experiments in the batch reactor. This co-solvent was not suitable for the use in microreactor because a stable parallel or segmented flow could not be achieved (Sudar et al., 2013a) and thus the experiments in microreactor were carried out with acetonitrile. The aldolase retains 80% of its activity in 5% of acetonitrile and 100% in ethyl acetate (Figure 2). Furthermore, the selection of organic solvent does not influence the equilibrium substrate conversion at concentrations below 10% v/v, consistent with the results shown in our previous work (Sudar et al., 2013a).