Copper removal by dry and re-hydrated biomass of Spirulina platensis.

Dried and re-hydrated biomass of Spirulina platensis was employed as a sorbent in tests of copper removal from water. Biomass re-hydrated for 24 h before use exhibited a shorter adsorption time as well as an increased percentage removal when compared with simply dried biomass. The combined effects of the concentrations of re-hydrated biomass (from 1.0 to 4.0 g l-1) and copper (from 0.1 to 0.4 g l-1) were then investigated. Copper was almost entirely removed (91% removal) at relatively high biomass levels (X0>or=2.0 gDM l-1), while 1.0 gDM l-1 removed only 81% of copper present initially, suggesting a situation of excess metal with respect to the adsorption capacity of biomass. Additional tests performed with biomass re-hydrated for variable time demonstrated that no less than 48 h of this treatment are needed to ensure a satisfactory copper removal, while no significant improvement was detected using biomass re-hydrated for longer times.

Synthesis of ethyl phenylacetate by lyophilized mycelium of Aspergillus oryzae.

Lyophilized mycelia of Aspergillus oryzae CBS 102.07, Aspergillus oryzae MIM, Rhizopus oryzae CBS 112.07, Rhizopus oryzae CBS 391.34, Rhizopus oryzae CBS 260.28 and Rhizopus oryzae CBS 328.47 were tested in this study to select the best biocatalysts for ethanol acylation with phenylacetic acid. The mycelium-bound carboxylesterase activity of A. oryzae MIM, which exhibited the best performances, was initially investigated at 50 degrees C, either in 0.1 M phosphate buffer or in n-heptane to catalyse the hydrolysis or the synthesis, respectively, of ethyl phenylacetate. The results in terms of product and substrate concentrations versus time were used to estimate the maximum molar conversions at equilibrium, the equilibrium constants, and the times needed to reach half maximum conversions, thus providing sufficient information about this biotransformation. The values of the apparent equilibrium constants, estimated at 20 degrees C

Nitrate and phosphate removal by Spirulina platensis.

The cyanobacterium Spirulina platensis was used to verify the possibility of employing microalgal biomass to reduce the contents of nitrate and phosphate in wastewaters. Batch tests were carried out in 0.5 dm3 Erlenmeyer flasks under conditions of light limitation (40 micromol quanta m(-2) s(-1)) at a starting biomass level of 0.50 g/dm3 and varying temperature in the range 23-40 degrees C. In this way, the best temperature for the growth of this microalga (30 degrees C) was determined and the related thermodynamic parameters were estimated. All removed nitrate was used for biomass growth (biotic removal), whereas phosphate appeared to be removed mainly by chemical precipitation (abiotic removal). The best results in terms of specific and volumetric growth rates (mu=0.044 day(-1), Qx=33.2 mg dm(-3) day(-1)) as well as volumetric rate and final yield of nitrogen removal (Q(N-NO3-)=3.26 mg dm(-3) day(-1), Y(N-NO3-)=0.739) were obtained at 30 degrees C, whereas phosphorus was more effectively removed at a lower temperature. In order to simulate full-scale studies, batch tests of nitrate and phosphate removal were also performed in 5.0 dm3 vessels (mini-ponds) at the optimum temperature (30 degrees C) but increasing the photon fluence rate to 80 micromol quanta m(-2) s(-1) and varying the initial biomass concentration from 0.25 to 0.86 g/dm3. These additional tests demonstrated that an increase in the inoculum level up to 0.75 g/dm3 enhanced both NO3- and PO4(3-) removal, confirming a strict dependence of these processes on biomass activity. In addition, the larger surface area of the ponds and the higher light intensity improved removal yields and kinetics compared to the flasks, particularly concerning phosphorus removal (mu=0.032-0.050 day(-1), Qx=34.7-42.4 mg dm(-3) day(-1), Q(N-NO3-)=3.24-4.06 mg dm(-3) day(-1), Y(N-NO3-)=0.750-0.879, Q(P-PO4(3-))=0.312-0.623 mg dm(-3) day(-1), and Y(P-PO4(3-))=0.224-0.440).

Effects of temperature, inoculum size and starch hydrolyzate concentration on butanediol production by Bacillus licheniformis.

An optimization study has been performed on 2,3-butanediol production by Bacillus licheniformis NCIMB 8059 from different carbon sources (glucose, sucrose and cornstarch hydrolyzate), alternately varying temperature (34

Treatment of effluent containing micropollutants by means of activated carbon.

Different amounts of granular activated carbon (GAC) have been tested for the removal of aliphatic and aromatic micropollutants contained in a liquid stream coming from an industrial plant. Tests have been carried out in a JAR-Test apparatus, using plugged flasks, in order to eliminate the oxygen influence on the adsorption process and to obtain information for studying the process in a pilot plant. The removal of aliphatic compounds resulted better than aromatic ones, probably because these substances are enveloped by water molecules which make adsorption on the GAC surface easier; in contrast, aromatic compounds show a lower affinity for the GAC, owing to their steric conformation. The good results obtained confirm that the proposed system is applicable to the examined effluent, even when the concentration of the pollutant load varies. In the latest part of this work, a plan for the construction of a full-scale plant to treat the examined wastewater has been developed.

Kinetics of alcohol fermentations carried out in rotating biological surface reactors.

This article aims at deriving kinetic models for the RBS reactor operating with and without cell porous support. Since derivation of the kinetic equations from the Monod model is very complex, an empirical derivation from experimental data of continuous alcohol fermentations is used in this work.

A kinetic study of Saccharomyces strains: Performance at high sugar concentrations.

Alcoholic fermentation represents a significant example of production of compounds utilizable as alternative energy sources. High ethanol concentration in the fermented wort is needed in order to reduce the energy consumption in the process of alcohol recovery. A particular Saccharomyces strain, of the oviformis species, obtained from fermented worts exhibiting high ethanol concentrations is studied and compared with a common S. cerevisiae strain in order to show its skill in fermenting very concentrated sugar solutions with an energy saving of ca. 10%.

Continuous alcohol fermentation in an immobilized cell rotating disk reactor.

The increasing interest in alcohol fermentation over these last years because of the energy crisis has been demonstrated by an increase in scientific research. After a brief analysis of the main results of the literature in the field of alcohol fermentation reactors, the use of a new type of immobilized cell reactor [the rotating biological surface (RBS) reactor] was studied. As is well known, the RBS reactor is a form of fixed-film reactor and can be described as a dynamic trickling filter. Our experimental apparatus employed a spongy material to trap the yeast cells on the disks. The results of fermentations carried out in the RBS reactor working in batch, in continuous with cell support, and in continuous without cell support have been presented in order to compare the different productivities and to assess the performance of the RBS immobilized cell reactor. An ethanol productivity of 7.1 g/L h was achieved in the RBS-ICR at a dilution rate of 0.3 h(-1), 2.5 times higher than the maximum productivity obtained in the RBS reactor without support at a lower dilution rate. The adoption of a spongy material as a cell immobilizer, combined with the use of the RBS reactor, enhances the particular advantages of both systems.