Bioconversion of <i style="">Amorphophallus campanulatus</i> to citric acid by <i style="">Aspergillus niger</i>–Effect of metal ions on fermentation, modelling studies and correlation of theoretical and experimental parameters

246-250 Amorphothallus campanulatus tuber was used as an efficient substrate for citric acid production by batch fermentation using Aspergillus niger. The amount of citric acid produced was compared with that produced from glucose as substrate. To scale up the bioprocess, transition metal ions such as Cr, Mo, Cd and Pb were added at optimum concentration as nutritional supplements and their effect on the biosynthetic route of the citric acid cycle was observed. Experimentally observed growth stages were used for mathematical modelling to evaluate the kinetic parameters. The calculated values agreed well with the observed ones. </smarttagtype

<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place" downloadurl="http://www.5iantlavalamp.com/"> Effect of transition metal ions on the metabolism of <i style="">Aspergillus niger</i> in the production of citric acid with molasses as substrate </smarttagtype></smarttagtype>

125-128 A two-stage process for the treatment of molasses was employed. Early germination with rapid multiplication of the microbe was observed. The nutritional quality of the medium was enriched by the addition of certain transition metal ions (Cr, Fe, Co, Ni, Cu, Mo, Cd & Pb), of which Ni was found to serve as a good nutritional supplement. Batch fermentations by surface culture were carried out and the possible mechanism for the metabolic changes taking place in Aspergillus niger during the production of citric acid is discussed. Using nickel, as high as 269 mg/ml of citric acid was produced. </smarttagtype

<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"> Growth kinetics of heavy metal adapted <i style="">Aspergillus niger</i> during citric acid biosynthesis </smarttagtype></smarttagtype>

610-613 The tolerance limit of Aspergillus niger NRRL 322 for the heavy metals like, Cd, Pb, Cr and Mo is analyzed as a part of the batch fermentation study undertaken. Computation of the kinetic parameters like, growth rate ( ), specific growth rate ( max), the saturation constant for the limiting nutrient (Ks), the growth yield (K), the growth lag (L) and the lag time (Tl) are done and correlated with the microbial metabolism. A detailed study on the growth rate of Aspergillus niger with glucose as the substrate in the presence of transition metals is done and the subsequent excretion of metabolic products associated with the growth in a batch fermentation are discussed. Hitherto reports document the growth yield of a microbe to be constant only with organic sources, but surprisingly, the growth yield of the strain is observed to be constant with an inorganic source like, Cd. Among the metal ions tried for batch fermentation, trial order of growth yield is found to be Mo > Cr > Pb > Cd and the biosynthesis of citric acid is more with Cd as a stimulant. </smarttagtype

Bioconversion of <i>Colocasia antiquorum </i>and <i>Aponogetonnatans </i>to Citric Acid by <i>Aspergillus niger </i>— Effect of Metal Ions and Kinetics

447-452Tuber crops belonging to the family Araceae namely Colocasia antiquorum and Aponogetonnatans are cultivated in large quantities for their edible portion. In this work, tubers are suitably treated and used as efficient substrates for citric acid production by fermentation using Aspergillus niger. The quantities of citric acid produced using these materials as substrates for bioconversion using Aspergillus niger are compared with those produced in synthetic medium comprising glucose as substrate.Transition metal ions such as , chromium, molybdenum, cadmium and lead are added at optimum concentration as nutritional supplements and their effect on the biosynthetic route of the citric acid cycle are discussed. Experimentally observed growth stages are used for mathematical modeling to evaluate the kinetic parameters. The values obtained by calculation agree well with the observed ones

Effect of transition metal cations and anions on the production of citric acid by <i>Aspergillus niger</i>

508-512Interest in studying the effect of microelements on the metabolism of fungi during the bioconversion has led to this work. The present work reports the production of citric acid starting from glucose by Aspergillus niger. The microelements supplemented were cadmium, lead, chromium and molybdenum. The bioconversion path of Aspergillus niger was TCA cycle. The products of the microbial metabolism namely total titrable acidity, citric acid, succinic acid, malic acid, intracellular proteins, extracellular proteins, amylase activity, lipid and biomass contents were determined periodically. Among the nutritional supplements tried cadmium was found to drive the metabolism of Aspergillus niger to produce more amount of citric acid. Experimentally observed growth stages were used for mathematical modelling to explore kinetic parameters. The values calculated based on the model were found to agree well with the observed ones in the case of lead and cadmium as supplements, whereas in the case of molybdenum and chromium deviations occur between the calculated and observed values. This discrepancy in the values of metabolic products was ascribed to the pH, temperature and other inhibitory products formed during fermentation. </span

Aqueous solutions of organic acids as effective solvents for levodopa extraction from mucuna pruriens seeds

Levodopa is an amino acid commonly used in the treatment of Parkinson’s disease found in several plants, such as Mucuna pruriens. The extraction of levodopa from biomass has been achieved using methanol, ethanol:water mixtures in presence of ascorbic acid, chloroform in alkaline media, and acetonitrile. Aiming at finding more sustainable solvents and develop efficient extraction processes, in this work, aqueous solutions of carboxylic acids (acetic, propionic, citric, glycolic, and lactic acid) and (poly)alcohols (ethanol, ethylene glycol and glycerol) were studied for the extraction of levodopa from Mucuna pruriens seeds. An initial screening with aqueous solutions of these compounds (at 50 wt%) was conducted at 50 °C, with an extraction time of 90 min at a solid/liquid (biomass/solvent) ratio of 1:10. Based on these results, citric acid aqueous solutions were identified as the best solvent, and an experimental design was carried out to optimize the temperature (T), solid/liquid ratio (S:L) and concentration of acid (wt.%), with the following optimal extraction conditions found: T = 60 °C, S:L = 1:7 and concentration of acid at 58 wt%. Under these optimal conditions, an extraction efficiency of 9.2 ± 0.1 wt% of levodopa was achieved. The recovery of levodopa from the acidic aqueous solution was achieved using an ion exchange column, allowing the recovery of approximately 84% of levodopa. The solvent was shown to be reusable in three successive extraction cycles, with no significant losses in the extraction efficiency of levodopa. The results here obtained show that citric acid aqueous solutions can lead to the effective extraction of levodopa from seeds of Mucuna pruriens, serving as basis for the development of more effective and environmentally friendly processes to recover natural products with therapeutic properties.publishe