Carob pod: A new substrate for citric acid production by Aspergillus niger

The production of citric acid from carob pod extract byA. niger in surface fermentation was investigated. A maximum citric acid concentration (85.5 g/L), citric acid productivity (4.07 g/L/d), specific citric acid production rate (0.18 g/g/d), and specific sugar uptake rate (0.358 g/g/d) was achieved at an initial sugar concentration of 200 g/L, pH of 6.5, and a temperature of 30°C. Other kinetic parameters, namely, citric acid yield, biomass yield, specific biomass production rate, and fermentation efficiency were maximum at pH 6.5, temperature 30°C, and initial sugar concentration 100 g/L. The external addition of methanol into the carob pod extract at a concentration up to 4% (v/v) improved the production of citric acid.     

Immobilization,characterization, and laboratory-scale application of bovine liver arginase

Arginase isolated from beef liver was covalently attached to a polyacrylamide bead support bearing carboxylic groups activated by a water-soluble carbodiimide. The most favorable carbodiimide wasN-cyclohexyl-Nt’-(methyl-2-p-nitrophenyl-2-oxoethyl) aminopropyl carbodiimide methyl bromide, but for practical purposes,N-cyclohexyl-Nt’-morpholinoethyl carbodiimide methyl tosylate was used. The optimal conditions for the coupling procedure were determined. The catalytic activity of the immobilized arginase was 290–340 U/g solid or 2.9–3.4 U/mL wet gel. The pH optimum for the catalytic activity was pH 9.5, the apparent temperature maximum was at 60°C and K_mapp was calculated to be 0.37M L-arginine. Immobilization markedly improved the conformational stability of arginase. At 60°C, the pH for maximal stability was found to be 8.0. The immobilized arginase was used for the production of L-ornithine and D-arginine.     

Interactions of water and methanol with a mixture of copper and zinc metals: a theoretical <Emphasis Type="Italic">ab initio</Emphasis> study

Ab initio cluster quantum chemical calculations at the Hartree–Fock and second-order Møller–Plesset perturbation theory levels were carried out to mimic the interactions of water and methanol with a mixture of Cu and Zn metals. It was shown that both molecular and dissociative adsorption of methanol on a mixture of Cu and Zn metal catalyst are preferred over the corresponding adsorptions of water. Estimated transition-state structures for dissociation of methanol into CH·₃ and OH· lie about 9.0 and 22.0 kcal/mol higher compared to the dissociated (forward reaction) and molecular adsorption (reverse reaction) complexes, respectively. Based on distinct radicals' bond energies with the active sites of the catalyst considered, it is suggested that hydrogen molecules could be formed through a chain of homogeneous reactions of methyl radicals released into the gas phase with the water and/or methanol molecules.     

A new diarylheptanoid and a new diarylheptanoid glycoside isolated from the roots of Juglans mandshurica and their anti-inflammatory activities

A new diarylheptanoid, (2S,3S,5S)-2,3,5-trihydroxy-1,7-bis(4-hydroxy- 3-methoxyphenyl)heptane (1), and a new diarylheptanoid glycoside, (2S,3S,5S)-2,3-dihydroxy-5-O-β-d-xylopyranosyl-7-(4-hydroxy-3-methoxyphenyl)-1-(4-hydroxyphenyl)heptane (2), together with three known compounds, rhoiptelol C (3), rhoiptelol B (4) and 3′,4″-epoxy-2-O-β-d-glucopyanosyl-1-(4-hydroxyphenyl)- 7-(3-methoxyphenyl)heptan-3-one (5) were isolated from the roots of Juglans mandshurica (Juglandaceae). The structures of compounds 1 and 2 were identified based on HR-ESI-MS, 1D and 2D NMR spectroscopic methods. Compounds 1–5 were assayed for their inhibitory effects on the production of NO, TNF-α and IL-6 in LPS-stimulated RAW264.7 cells.     

Production of α-keto acids Part I. Immobilized cells ofTrigonopsis variabilis containing D-amino acid oxidase

Whole cells ofTrigonopsis variabilis were immobilized by entrapment in Ca²⁺-alginate and used for the production of α-keto acids from the corresponding D-amino acids. The D-amino acid oxidase within the immobilized cells has a broad substrate specificity. Hydrogen peroxide formed in the enzymatic reaction was efficiently hydrolyzed by manganese oxide co-immobilized with the cells. The amino acid oxidase activity was assayed with a new method based on reversed-phase HPLC. Oxygen requirements, bead size, concentration of cells in the beads, flow rate, and other factors were investigated in a “ trickle-bed ” reactor.     

Glucose utilization by lysine-producing fluoroacetate-sensitive mutants ofCorynebacterium glutamicum

A fluoroacetate-sensitive mutant was isolated fromCorynebacterium glutamicum, ATCC 21513, following mutagenesis with NTG. Batch fermentations show that in terms of growth kinetics, glucose utilization, and lysine formation, there are significant differences between the mutant and the parent. The mutant’s specific growth rate (0.22/h) is lower than that for the parent (0.34/h). Also, the yield expressed as lysine/glucose consumed does not alter as a function of the glucose concentration for the mutant, and is about 0.22, whereas for the parent, this coefficient decreases with increasing glucose concentration. The maximum specific rate of lysine production for the mutant is 1.3 g/L/h that is about two-fold higher than that for the parent.     

Continuous fermentation for the production of citric acid from glucose

Citric acid is finding new areas of use each year and the demand for the acid is constantly increasing. Being a bulk chemical, the continuous production of citric acid would be advantageous. The paper presents the results from ammonia limited batch and continuous fermentations using the yeast strainSaccharomycopsis (Candida) lipolytica (NRRL Y-7576). Mathematical models were developed for growth and glucose utilization in batch and continuous culture. Cell and acid yields appeared to be almost the same in batch and continuous culture. The specific production rates were found to be constant, equal to 0.053 g/g h, in the batch fermentations but varied in the continuous experiments from 0 to 0.11 g/g h depending on the fermentation conditions. Continuous production in a single stage CSTR was studied for over 1,000 hours without shutdown.     

Catalysis in Organic Solvents with Lipase Immobilized by Sol-Gel Technique

A series of immobilized lipases were obtained by sol-gel process, using silica prepolymers prepared from tetramethoxysilane, methyltrimethoxysilane, propyltrimethoxysilane and (3-aminopropyl)triethoxysilane. The activities of these biocatalysts were compared with the lipase adsorbed on poly(methylhydroxysiloxane) and encapsulated into a silicone rubber, lipase entrapped in nanoporous silica matrix and commercial sol-gel lipase. Model reactions were the esterification of stearic acid and Corey lactone bisalcohol (an intermediate of prostaglandin synthesis). The positive effect of hydrophobic-hydrophilic interface, created by the addition of organosilanes, on the activity of biocatalysts was partially reduced by decreasing specific surface of mesopores. Hydrophobic solvents increased the activity of the lipase entrapped in tetramethoxysilane–methyltrimethoxysilane prepolymer in the sequence acetone < toluene < benzene < decane < hexane. The activity of silicone rubber-encapsulated biocatalysts was proportional to polymer swelling in organic solvents (hexane > toluene > acetone).     

Production and energetic use of biogas from energy crops and wastes in Germany

The production of biogas for reducing fossil CO₂ emissions is one of the key strategic issues of the German government and has resulted in the development of new process techniques and new technologies for the energetic use of biogas. Progress has been made in cultivating energy crops for biogas production, in using new reactor systems for anaerobic digestion, and in applying more efficient technologies for combined heat and power production. Recently, integration of fuel cells within the anaerobic digestion process was started, and new technologies for biogas upgrading and conversion to hydrogen were tested. This article describes the trends in Germany for achieving more efficient energy production.     

Autonomously Propelled Motors for Value‐Added Product Synthesis and Purification

A proof‐of‐concept design for autonomous, self‐propelling motors towards value‐added product synthesis and separation is presented. The hybrid motor design consists of two distinct functional blocks. The first, a sodium borohydride (NaBH₄) granule, serves both as a reaction prerequisite for the reduction of vanillin and also as a localized solid‐state fuel in the reaction mixture. The second capping functional block consisting of a graphene–polymer composite serves as a hydrophobic matrix to attract the reaction product vanillyl alcohol (VA), resulting in facile separation of this edible value‐added product. These autonomously propelled motors were fabricated at a length scale down to 400 μm, and once introduced in the reaction environment showed rapid bubble‐propulsion followed by high‐purity separation of the reaction product (VA) by the virtue of the graphene–polymer cap acting as a mesoporous sponge. The concept has excellent potential towards the synthesis/isolation of industrially important compounds, affinity‐based product separation, pollutant remediation (such as heavy metal chelation/adsorption), as well as localized fuel‐gradients as an alternative to external fuel dependency.