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The aim of this study was to investigate the performance of bench-scale packed-bed reactors for hydrogenotrophic denitrification with hydrogen produced from electrolysis of water and electric energy provided by a solar cell. Two configurations were used, a single filter and a triple-column reactor, with gravel of different sizes as support media. The effect of hydrogen and carbon dioxide supply on the performance of the two systems of bioreactors under continuous operation was examined. The multi-filter system achieved high performances as it could safely treat polluted water with a low hydrogen and carbon dioxide consumption. A denitrification rate of 2 kg/m3d was achieved for nitrate nitrogen and hydraulic loading of 1.44 g NO-3-N/d and 11.5 m3/m2d, respectively. Also, a mathematical model was developed by using growth kinetics expressions for four-nutrient limitation (nitrate, nitrite, hydrogen and carbon dioxide) with inhibition by nitrate. The proposed model is capable of describing accurately enough, hydrogenotrophic denitrification under continuous operation. [ABSTRACT FROM AUTHOR]

The article discusses research concerning the use of the oleaginous fungus Mortierella isabellina from a sweet sorghum extract in single-cell oil (SCO) production. Details about the extraction and formulation of culture media are presented. Biomass and nitrogen are some of the elements determined during the evaluation of concentrations. The observed influence of sugars on microbial growth is also explored.

Abstract: Rice hull hydrolysate was used as feedstock for microbial lipids production using the oleaginous fungus Mortierella isabellina. Kinetic experiments were conducted in C/N ratios 35, 44 and 57 and the oil accumulation into fungal biomass was 36%, 51.2% and 64.3%, respectively. A detailed mathematical model was used in order to describe the lipid accumulation process. This model was able to predict reducing sugar and nitrogen consumption, fat-free biomass synthesis and lipid accumulation. Neutral lipids constitute the predominant lipid fraction, while the major fatty acids were oleic, palmitic and linoleic acid. Fatty acids of long aliphatic chain were not detected, thus the microbial oil produced is a promising feedstock for biodiesel production. [Copyright &y& Elsevier]

Abstract: Several approaches of hydrogenotrophic denitrification of potable water as well as technical data and mathematical models that were developed for the process are reviewed. Most of the applications that were tested for hydrogenotrophic process achieved great efficiency, high denitrification rates, and operational simplicity. Moreover, this paper reviews the variety of reactor configurations that have been used for hydrogen gas generation and efficient hydrogen delivery. Microbial communities and species that participate in the denitrification process are also reported. The variation of nitrate concentration, pH, temperature, alkalinity, carbon and microbial acclimation was found to affect the denitrification rates. The main results regarding research progress on hydrogenotrophic denitrification are evaluated. Finally, the commonly used models and simulation approaches are discussed. [Copyright &y& Elsevier]

Abstract: An oleaginous fungus, Mortierella isabellina, able to transform efficiently sugar to storage lipid, was used as a model microorganism which develops a biofilm structure during the semi-solid fermentation process for the production of biodiesel from sweet sorghum. A mathematical model was developed to describe the fungal oil production in M. isabellina biofilm. The model describes diffusion and consumption of sugars and nitrogen of sweet sorghum and single cell oil production in a biofilm, which grows according to the kinetics of double-substrate limitation (sugars and nitrogen) with sugar inhibition. Experimental data from a previous experimental study were used to determine the kinetic parameters of the model. Maximum biofilm thickness and the percentage of lipid inside the biofilm were estimated using the model at 1892μm and 15%, respectively. The proposed mathematical model could prove a useful tool for designing semi-solid fermentation processes. [Copyright &y& Elsevier]

Biodegradation in porous media is studied with carefully controlled and well-characterized experiments in model porous media constructed of etched glass. Porous media of this type allow visual observation of the phenomena that take place at pore scale. An aqueous solution of five organic pollutants (toluene, phenol, o-cresol, naphthalene and 1,2,3-trimethylbenzene) was used as a model NAPL (representing creosote). The bacteria used were Pseudomonas fluorescens, which are indigenous (even predominant) in many contaminated soils. The maximum aqueous concentrations of the specific organic substances, below which biodegradation becomes possible, were determined as a function of temperature from toxicity experiments. Visualization experiments were made under various flow velocities and organic loadings to study the morphology and thickness of the biofilm as a function of the pore size and the distance from the entrance, and the efficiency of biodegradation. The efficiency of biodegradation decreased as the aqueous concentration of NAPL at the inlet increased and/or as the flow velocity increased. The thickness of biofilm decreased as the distance from the inlet increased and/or the pore diameter decreased. A quasi-steady-state theoretical model of biodegradation was used to calculate the values of the mesoscopic biochemical rates and to predict the profile of NAPL concentration in the porous medium and the thickness of biofilm in pores. The agreement between experimental data and model predictions is quite satisfactory. [Copyright &y& Elsevier]