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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clostridium thermohydrosulfuricum consumed glucose in preference to cellobiose as an energy source for growth. The rates of substrate uptake in glucose- and cellobiose-grown cell suspensions were 45 and 24 nmol/min per mg (dry weight), respectively, at 65 degrees C. The molar growth yields (i.e., grams of cells per mole of glucose equivalents) were similar on cellobiose and glucose (19 and 16, respectively). Both glucose- and cellobiose-grown cells contained a glucose permease activity and high levels of hexokinase (greater 0.34 mumol/min per mg of protein at 40 degrees C). Growth on cellobiose was associated with induction of a cellobiose permease activity. In contrast, Clostridium thermocellum metabolized cellobiose in preference to glucose as an energy source and displayed lower growth rates on both substrates. The substrate uptake rates in cellobiose- and glucose-grown cell suspensions were 18 and 17 nmol/min per mg (dry weight), respectively. The molar yields were 38 on cellobiose and 20 on glucose. Extracts of glucose- and cellobiose-grown cells both contained cellobiose phosphorylase and phosphoglucomutase activities, whereas only glucose-grown cells contained detectable levels of glucose permease and hexokinase activities. The general catalytic and kinetic properties of the glucose- and cellobiose-catabolizing enzymes in the two species are described, and a model is proposed to distinguish differential saccharide metabolism by these thermophilic ethanologens.
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PMID:Differential metabolism of cellobiose and glucose by Clostridium thermocellum and Clostridium thermohydrosulfuricum. 621 Jun 89

An adhE, ldhA double mutant Escherichia coli strain, SBS110MG, has been constructed to produce succinic acid in the presence of heterologous pyruvate carboxylase (PYC). The strategic design aims at diverting maximum quantities of NADH for succinate synthesis by inactivation of NADH competing pathways to increase succinate yield and productivity. Additionally an operational PFL enzyme allows formation of acetyl-CoA for biosynthesis and formate as a potential source of reducing equivalents. Furthermore, PYC diverts pyruvate toward OAA to favor succinate generation. SBS110MG harboring plasmid pHL413, which encodes the heterologous pyruvate carboxylase from Lactococcus lactis, produced 15.6 g/L (132 mM) of succinate from 18.7 g/L (104 mM) of glucose after 24 h of culture in an atmosphere of CO(2) yielding 1.3 mol of succinate per mole of glucose. This molar yield exceeded the maximum theoretical yield of succinate that can be achieved from glucose (1 mol/mol) under anaerobic conditions in terms of NADH balance. The current work further explores the importance of the presence of formate as a source of reducing equivalents in SBS110MG(pHL413). Inactivation of the native formate dehydrogenase pathway (FDH) in this strain significantly reduced succinate yield, suggesting that reducing power was lost in the form of formate. Additionally we investigated the effect of ptsG inactivation in SBS110MG(pHL413) to evaluate the possibility of a further increase in succinate yield. Elimination of the ptsG system increased the succinate yield to 1.4 mol/mol at the expense of a reduction in glucose consumption of 33%. In the presence of PYC and an efficient conversion of glucose to products, the ptsG mutation is not indispensable since PEP converted to pyruvate as a result of glucose phosphorylation by the glucose specific PTS permease EIICB(glu) can be rediverted toward OAA favoring succinate production.
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PMID:Efficient succinic acid production from glucose through overexpression of pyruvate carboxylase in an Escherichia coli alcohol dehydrogenase and lactate dehydrogenase mutant. 1580 71