J. M. Novais

Supercritical CO2 extraction of carotenoids and other lipids from Chlorella vulgaris

Freeze-dried samples of the microalga Chlorella vulgaris were submitted to supercritical CO2 at temperatures of 40 and 55 °C and pressures up to 35.0 MPa. This study was carried out on whole and crushed algae. The extraction yields of carotenoids and other lipids were low in the former case and improved significantly in the latter one. Extraction yields of carotenoids and other lipids increased with pressure. The fraction of carotenoids in the oil was also greater at higher pressures. On the other hand, supercritical CO2 extraction of carotenoids compared favourably with hexane and acetone extractions.

Effect of some operational parameters on textile dye biodegradation in a sequential batch reactor.

The combination of anaerobic and aerobic periods in the operation cycle of a Sequencing Batch Reactor (SBR) was chosen to study biological color removal from simulated textile effluents containing reactive, sulfonated, monoazo and diazo dyes, respectively, Remazol Brilliant Violet 5R and Remazol Black B. 90% color removal was obtained for the violet dye in a 24-h cycle with a Sludge Retention Time (SRT) of 15 days and an aerated reaction phase of 10 h. For the black dye only 75% color removal was achieved with the same operational conditions and no improvement was observed with the increase of the SRT to 20 days. For the violet dye a reduction of the color removal values from 90 to 75% was observed with the increase of the aerated reaction phase from 10 to 12 h. However, this increase did not promote the aerobic biodegradation of the produced aromatic amines. Abiotic tests were performed with sterilized SBR samples and no color removal was observed in cell-free supernatants. However color removal values of 30 and 12% were observed in the presence of sterilized cells and supernatants with violet and black dye, respectively and could be attributed to the presence of active reducing principles in the sterilized samples.

Constructed wetlands for the treatment of organic pollutants

BackgroundConstructed wetlands (wetland treatment systems) are wetlands designed to improve water quality. They use the same processes that occur in natural wetlands but have the flexibility of being constructed. As in natural wetlands vegetation, soil and hydrology are the major components. Different soil types and plant species are used in constructed wetlands. Regarding hydrology surface flow and subsurface flow constructed wetlands are the main types. Subsurface flow constructed wetlands are further subdivided into horizontal or vertical flow. Many constructed wetlands deal with domestic wastewater where BOD and COD (Biochemical and Chemical Oxygen Demand respectively) are used as a sum parameter for organic matter. However, also special organic compounds can be removed.ObjectiveThe objectives are to summarise the state-of-the-art on constructed wetlands for treatment of specific organic compounds, to the present the lack of knowledge, and to derive future research needs.MethodsCase studies in combination with a literature review are used to summarise the available knowledge on removal processes for specific organic compounds.Results and DiscussionCase studies are presented for the treatment of wastewaters contaminated with aromatic organic compounds, and sulphonated anthraquinones, olive mill wastewater, landfill leachate, and groundwater contaminated with hydrocarbons, cyanides, chlorinated volatile organics, and explosives. In general the removal efficiency for organic contaminants is high in all presented studies.ConclusionConstructed wetlands are an effective and low cost way to treat water polluted with organic compounds. There is a lack of knowledge on the detailed removal pathways for most of the contaminants. Removal rates as well as optimal plant species are substance-specific, and also typically not available. If a constructed wetland provides different environmental conditions and uses different plant species the treatment efficiency can be improved.Recommendations and OutlookThere is a great need to lighten the black box ‘constructed wetland’ to obtain performance data for both microbial activity and the contribution of the plants to the overall removal process. Also genetic modified plants should be considered to enhance the treatment performance of constructed wetlands for specific compounds.

Evolution of pigment composition in Chlorella vulgaris

The onset of carotenogenesis in Chlorella vulgaris and the change in nature and concentration of pigments with time was studied. The succession of pigments observed was interpreted in terms of relative efficiencies of carotenoid interconversion pathways, and this might be used to monitor the progress of the carotenogenic process. This work is relevant to the use of dry Chlorella biomass, as a naturally encapsulated form of a natural colouring ingredient, in animal feed.

Degradation of phenol by immobilized cells ofFusarium flocciferum

SummaryThe degradation of phenol by cells ofFusarium flocciferum immobilized by entrapment in agar, K — carrageenan, alginate and polyurethane, and by adsorption on preformed polyurethane foams was investigated. Entrapped and adsorbed cells in polyure —thane were able to degrade phenol up to 4g/l and 2.5g/l respectively with no loss of their activity under repetead use for more than two months.

FLOCS VS GRANULES: DIFFERENTIATION BY FRACTAL DIMENSION

Abstract High rate anaerobic wastewater treatment systems usually give rise to biomass structured in different types of aggregates, depending on prevalent environmental conditions. Although highly dependent on wastewater characteristics, granules are generally formed and found in UASB reactors, whereas flocs are mainly found in fixed bed reactors. Different structures usually have different shapes and surface roughness. The aim of this work is to provide a contribution to the differentiation of those kinds of aggregates. A numerical parameter, the fractal dimension, was used to quantify the surface roughness. The fractal dimension, of two families of particles, was measured by two methods: (i) a box counting method; (ii) a method based on an area-size relationship. In both cases, the differences were highly statistically significant. Using the box counting method, for each of the 54 particles of each family, the average fractal dimension was 1.90 ± 0.02 for flocs and 1.95 ± 0.01 for granules (±99% confidence interval). The log-log plot of area vs longest size was linear and the calculated fractal dimensions from this plot were 1.84 ± 0.13 and 2.14 ± 0.08 (±99% confidence interval) for flocs and granules, respectively. Fractal dimension was proven to be a suitable parameter to quantify and differentiate surface roughness of different microbial aggregates present in high rate anaerobic digesters.

Chlorella vulgarisused to Colour Egg Yolk

Dry biomass obtained from stressed cells of Chlorella vulgaris (rich in carotenoid pigments) was used as such in animal feed, instead of the commercial synthetic pigment. The in vivo effect of microalgal biomass as substitute pigment was ascertained with Hisex brown hens kept laying during 37 days under conventional conditions, and strongly suggested that yolk pigmentation was comparable to that obtained using commercial pigments, when comparable weight of colourant was formulated into the feed.

Influence of nitrogen source and photoperiod on exopolysaccharide synthesis by the microalga Botryococcus braunii UC 58

The high exopolysaccharide (EPS) producing microalga Botryococcus braunii UC 58 produced, under continuous illumination, higher concentrations of EPS (2.5 g l−1 after 14 days of growth) when nitrate was used as the nitrogen source instead of urea or ammonium (2 mm of nitrogen). In addition, broth viscosity decreased sharply with ammonium or urea when cultures entered the stationary phase, suggesting biopolymer hydrolysis. In the range 0.5–8 mm NO−3, nitrogen appeared to be the growth-limiting nutrient, as suggested by the onset of the stationary phase and the final biomass concentration. Over 30 days of culture, the specific EPS production (EPS produced per unit of biomass) was minimal for 8 mm NO−3 and similar for 0.5 and 2 mm possibly related to the increase in specific EPS synthesis along the exponential phase, reaching the highest levels after growth had stopped. Broth viscosity increased with growth accompanying EPS accumulation but sharply decreased a few days after the cultures entered the stationary phase. This decrease was observed earlier for cultures with lower NO−3 concentration. Considering a culture period above 10 days, the increase of NO−3 concentration up to 2 mm is recommended to reach higher EPS concentrations, but the use of 8 mm NO−3 is only of possible interest for extended growth periods (above 15 days). The introduction of a photoperiod led to delayed growth and EPS production. However, the specific production is similar when the same phase of growth is considered.

Temperature profiles of cellular growth and exopolysaccharide synthesis by Botryococus braunii Kütz. UC 58

Temperature profiles (range 20–33 °C) were obtained for growth and exopolysaccharide (EPS) biosynthesis of the microalga Botryococcus braunii strain UC 58 under photoautotrophic conditions. The maximum temperature for growth was 32 °C and the temperature dependence of the specific growth rate was described by the Hinshelwood equation based on the Arrhenius relationship. The optimal range of temperatures for growth and extracellular EPS synthesis (25–30 °C) concurred and production of 4.5–5 g l−1 of EPS was obtained routinely, leading to high broth viscosities. Below 23 °C EPS biosynthesis was negligible, although the specific growth rate maintained high values. At supraoptimal temperatures EPS biosynthesis decreased, accompanying the increase in doubling time.The polymers formed at temperatures within the optimal range for production, when dissolved in water, produced solutions (2 gl−1) with the highest viscosity, suggesting that their molecular weight showed the highest values. The degree of polymerization of the EPS synthesized at suboptimal and supraoptimal temperatures was significantly below the values within the optimal range.

Production of high concentration of ethanol from mash, juice and pulp of Jerusalem artichoke tubers by Kluyveromyces fragilis

The profile of batch ethanol production of Jerusalem artichoke tuber mash by a strain of Kluyveromyces fragilis was compared with that of the extracted juice and of the remaining pulp. Alcoholic fermentations were carried out at pH 4.5 without additives. Although K. fragilis is inhibited at added ethanol concentrations above 8% (v/v), the juice allowed the production of 12.8% (v/v) of ethanol in 70 h with the consumption of 95% of initial sugars and an ethanol yield 77% of the theoretical maximum. These high concentrations of ethanol are explained by protein supplementation mechanisms. Mash and pulp, although more difficult to handle than juice, led to the production in 70 h of 11.3 and 8.3% (v/v) of ethanol respectively, with the consumption of 87 and 80% of the initial sugars and ethanol yields of 81 and 84% of the theoretical maximum. Results indicate that the production of ethanol from the mash with and without prior extraction is feasible and may increase the total ethanol obtained by unit mass of tubers.