Aims: To analyse the production of different metabolites by dark-grown Euglena gracilis under conditions found to render high cell growth. Methods and Results: The combination of glutamate (5 g l⁻¹), malate (2 g l⁻¹) and ethanol (10 ml l⁻¹) (GM + EtOH); glutamate (7·15 g l⁻¹) and ethanol (10 ml l⁻¹); or malate (8·16 g l⁻¹), glucose (10·6 g l⁻¹) and NH₄Cl (1·8 g l⁻¹) as carbon and nitrogen sources, promoted an increase of 5·6, 3·7 and 2·6-fold, respectively, in biomass concentration in comparison with glutamate and malate (GM). In turn, the production of α-tocopherol after 120 h identified by LC-MS was 3·7 ± 0·2, 2·4 ± 0·1 and 2 ± 0·1 mg [g dry weight (DW)]⁻¹, respectively, while in the control medium (GM) it was 0·72 ± 0·1 mg (g DW)⁻¹. For paramylon synthesis, the addition of EtOH or glucose induced a higher production. Amino acids were assayed by RP-HPLC; Tyr a tocopherol precursor and Ala an amino acid with antioxidant activity were the amino acids synthesized at higher concentration. Conclusions: Dark-grown E. gracilis Z is a suitable source for the generation of the biotechnologically relevant metabolites tyrosine, α-tocopherol and paramylon. Significance and Impact of the Study: By combining different carbon and nitrogen sources and inducing a tolerable stress to the cell by adding ethanol, it was possible to increase the production of biomass, paramylon, α-tocopherol and some amino acids. The concentrations of α-tocopherol achieved in this study are higher than others reported previously for Euglena, plant and algal systems. This work helps to understand the effect of different carbon sources on the synthesis of bio-molecules by E. gracilis and can be used as a basis for future works to improve the production of different metabolites of biotechnological importance by this organism.

AS‐30D hepatoma cells, a highly oxidative and fast‐growing tumor line, showed glucose‐induced and fructose‐induced inhibition of oxidative phosphorylation (the Crabtree effect) of 54% and 34%, respectively. To advance the understanding of the underlying mechanism of this process, the effect of 5 mm glucose or 10 mm fructose on the intracellular concentration of several metabolites was determined. The addition of glucose or fructose lowered intracellular P_i (40%), and ATP (53%) concentrations, and decreased cytosolic pH (from 7.2 to 6.8). Glucose and fructose increased the content of AMP (30%), glucose 6‐phosphate, fructose 6‐phosphate and fructose 1,6‐bisphosphate (15, 13 and 50 times, respectively). The cytosolic concentrations of Ca²⁺ and Mg²⁺ were not modified. The addition of galactose or glycerol did not modify the concentrations of the metabolites. Mitochondria isolated from AS‐30D cells, incubated in media with low P_i (0.6 mm) at pH 6.8, exhibited a 40% inhibition of oxidative phosphorylation. The data suggest that the Crabtree effect is the result of several small metabolic changes promoted by addition of exogenous glucose or fructose.

Ethanol accumulation during fermentation contributes to the toxic effects in Saccharomyces cerevisiae, impairing its viability and fermentative capab

Mitochondrial calcium overload has been implicated in the irreversible damage of reperfused heart. Accordingly, we studied the effect of an oxygen‐bridged dinuclear ruthenium amine complex (Ru₃₆₀), which is a selective and potent mitochondrial calcium uniporter blocker, on mitochondrial dysfunction and on the matrix free‐calcium concentration in mitochondria isolated from reperfused rat hearts. The perfusion of Ru₃₆₀ maintained oxidative phosphorylation and prevented opening of the mitochondrial permeability transition pore in mitochondria isolated from reperfused hearts. We found that Ru₃₆₀ perfusion only partially inhibited the mitochondrial calcium uniporter, maintaining the mitochondrial matrix free‐calcium concentration at basal levels, despite high concentrations of cytosolic calcium. Additionally, we observed that perfused Ru₃₆₀ neither inhibited Ca²⁺ cycling in the sarcoplasmic reticulum nor blocked ryanodine receptors, implying that the inhibition of ryanodine receptors cannot explain the protective effect of Ru₃₆₀ in isolated hearts. We conclude that the maintenance of postischemic myocardial function correlates with an incomplete inhibition of the mitochondrial calcium uniporter. Thus, the chemical inhibition by this molecule could be an approach used to prevent heart injury during reperfusion.