J. de la Noüe

Factors affecting protein release from alginate-chitosan coacervate microcapsules during production and gastric/intestinal simulation.

A series of experiments was performed to evaluate the influence of a number of physico-chemical factors on the diffusion of a model protein, bovine serum albumin (BSA), from dried chitosan-coated alginate microcapsules. Diffusion of BSA was quantified during the microcapsule manufacture processes (gelation, washing, rinsing) and during incubation in conditions simulating the pH encountered during the gastric (0.1 N HCl; pH 1.5) and intestinal (200 mM Tris-HCl; pH 7.5) phases of digestion. Factors tested included alginate and chitosan concentration, calcium chloride (CaCl2) concentration in the gelation medium, loading rate, chitosan molecular mass and pH of the gelation medium. Microcapsule size and gelation time were altered in order to determine their effects on protein retention. Alginate and chitosan concentration significantly influenced BSA retention during microcapsule manufacture and acid incubation, as did calcium chloride concentration in the gelation medium (P<0.05). BSA retention during manufacture was not significantly altered by protein loading rate or pH of the encapsulation medium, however, protein retention during acid incubation decreased significantly with increasing protein loading rate and encapsulation medium pH (P<0.05). Microcapsules that were washed with acetone following manufacture demonstrated significantly increased protein retention during acid incubation (P<0.05). In microcapsules that had been acetone-dried to a point whereby their mass was reduced to 10% of that immediately following encapsulation, protein retention was over 80% following 24-h acid incubation vs. only 20% protein retention from non acetone-dried microcapsules. The presence of calcium in the neutral buffer medium significantly reduced BSA diffusion in a concentration-dependent manner (P<0.05).

Digestibility in fish: Improved device for the automatic collection of feces

Abstract An improved apparatus for the quantitative automatic collection of fish feces is presented. The drainage water from fish tanks is filtered through metallic screens that separate feces from water as they move linearly. With an abrupt stop of the screens, the feces are injected into a refrigerated pan where they are automatically frozen. The system is limited only by the capacity of the collector pans. With this quantitative recovery of feces, the direct method may be used for digestibility determinations on natural or artificial foodstuffs. Furthermore, this apparatus may be used with species where feces collection by abdominal pressure for digestibility measurements is not possible.

Histological and histochemical changes in the digestive tract of white sturgeon larvae during ontogeny

Ontogenetic changes in digestive tract histology and digestive enzyme histochemistry were investigated 11 to 36 days post-hatch in white sturgeon Acipenser transmontanus larvae. From initiation of exogenous feeding (12 days post-hatch), larvae were fed a commercial salmonid diet for the ensuing 24 days. The digestive system of white sturgeon displayed a high degree of morphologic organization and functionality at the onset of exogenous feeding. An enhancement of digestive capacities occurred with transition to active feeding. On day 2 of feeding, there was a clear increase of alkaline phosphatase, aminopeptidase M, dipeptidyl peptidase IV, and γ-glutamyl transpeptidase activity in the brush border of the spiral intestine. This strong activity is an apparent confirmation of the importance of this segment of the intestine for protein digestion and nutrient absorption. The functional development of the pyloric intestine occurred on day 4 and was concomitant with an increase in the activity of brush border and cytoplasmic enzymes such as acetylcholinesterase, dipeptidyl peptidase II, α- and β-galactosidases. The absence of acetylcholinesterase, lactase, nonspecific esterase, and weak activity of exopeptidases and alkaline phosphatase in the anterior intestine suggests that this segment of the intestine may be less important in nutrient absorption than the pyloric and spiral intestines. The observed quantitative and qualitative differences in enzyme activity along the intestine indicate a high degree of specialization of each segment for specific digestive and absorptive processes.

Nitrogen and phosphorus removal by high latitude mat-forming cyanobacteria for potential use in tertiary wastewater treatment

As part of a program to develop biological wastewatertreatment systems for cold climate areas four strainsof filamentous, mat-forming cyanobacteria isolatedfrom Arctic and Antarctic environments were evaluatedfor their nutrient stripping and growth capabilities. A tropical strain, Phormidium bohneri, known forits excellent performance in wastewater treatment, wasused as a comparison. Experiments were done inartificial media under controlled batch cultureconditions to avoid interactions with indigenousmicroorganisms such as bacteria and protozoa. Theculture medium simulated real effluents containinghigh concentrations of nitrate and phosphate.Temperatures (5, 15 and 25°C) and irradiances(80, 210, 350, 640 and 1470 µmol photon m-2s-1) wereselected according to situations encountered in avariety of field conditions. For all irradiancelevels, growth was satisfactory at 15 and 25 °C,but limited at 5 °C. At 25 °C a satisfactory nitrogen removal rate (3.5and 4.0 mg N L-1d-1) was obtained forone polar strain (Phormidium tenue) and thecontrol P. bohneri. At 15 °C, the bestnitrogen removal rate (3.5 mg N L-1d-1)was measured with P. bohneri while the best ratefor the polar strains was around 2.3 mg NL-1d-1. At 15 °C, a phosphorusremoval rate of 0.6 mg P L-1d-1 wasobtained with P. bohneri and polar strains P. tenue and Oscillatoria O-210. Nitrogen(NO3-) and phosphorus (PO43-)uptake rates increased as a function of irradianceover the range 80 to 350 μmolphoton m-2s-1. Our results indicate thattertiary biological wastewater treatment at lowtemperatures (5 °C) cannot be anticipated withthe polar strains tested, because they arepsychrotrophic rather than psychrophilic and thus growtoo slowly under conditions of extreme cold. However, it appears that these cyanobacteria would beuseful for wastewater treatment at moderately cooltemperatures (c. 15 °C), which are commonduring spring and fall in northern climates.

Harvesting marine microalgae species by chitosan flocculation

Abstract Marine microalgae are still an important larval feeding source. One of the most promising harvesting techniques of the algae produced appears to be chemical flocculation. We report results obtained with chitosan flocculation of five marine species of microalgae of importance to mariculture (Skeletonema costatum, Dunaliella tertiolecta, Thalassiosira nordenskoldii, Chlorella sp. and Thalassionema sp.). The algae were grown in the laboratory in 20-liter batch cultures under normal conditions in artificial seawater. Without pH control, a 100% flocculation efficiency was reached at fairly high chitosan concentrations (above 40 mg liter−1). When the final pH was adjusted to around 7·8–8·0, a 100% flocculation efficiency was obtained with chitosan concentrations of 40 mg liter−1 or more. However, when pH was adjusted to around 7 or less, prior to chitosan addition for S. costatum and Chlorella sp., the concentration of chitosan required to obtain a 95–100% flocculation efficiency was reduced to 20 mg liter−1 for Chlorella and 2 mg liter−1 for S. costatum. The results are discussed in the light of the currently accepted theories on flocculation.

Efficiency of immobilized hyperconcentrated algae for ammonium and orthophosphate removal from wastewaters

SummaryHyperconcentrated microalgae cultures (up to 3,29 g dry weight/L) were immobilized in kappa-carrageenan beads. It appears that entrapped algae are able to remove efficiently nitrogen and phosphorus from urban secondary effluent and then perform a tertiary wastewater treatment.

Tertiary treatment of wastewater with Phormidium bohneri (Schmidle) under various light and temperature conditions

Experiments were carried out on secondary effluents under different conditions of light and temperature with the aim of evaluating the potential and limits of the epilithic filamentous cyanobacterium Phormidium bohneri (Schmidle) for biotreatment of domestic wastewaters. Aerated cultures were incubated at 10 and 30°C in a chamber fitted with a photic gradient plate receiving 120 and 720 μE/m2s. Results indicate that the strain used prefers elevated temperatures, and can withstand considerable variation in light intensity. Response at 30°C with regard to NH3 and PO4−3 removal agrees with that reported for unicellular chlorophytes. A complete exhaustion of these nutrients was obtained after 3 and 5 days, respectively. It appears that NH3 stripping contributed substantially (38–100%) to the overall NH3 removal efficiency observed in the system. In addition, the protein and carbohydrate content of the biomass produced suggests potential feedstock use.

Hyperconcentrated cultures of Scenedesmus obliquus: A new approach for wastewater biological tertiary treatment?

Abstract Algal cultures of Scenedesmus obliquus at low concentrations (0.1–0.2 g dry wt l −1 ) provide adequate biological tertiary treatment of wastewaters. This research was aimed at studying the possibility of increasing the system performance by using hyperconcentrated cultures of S. obliquus (up to 2.6 g dry wt l −1 ) at the laboratory scale. The algal culture grown on secondary effluent was first chemically flocculated with chitosan (30 mg l −1 ) and decanted; the sedimented culture (5 g dry wt l −1 ) was then resuspended in secondary effluent to obtain algal suspensions at various concentrations, the performance of which was compared to that of a control culture (0.13 g dry wt l −1 ). The rate of exhaustion of nitrogen (N-NH 4 + ) was proportional to the algal concentration and a complete removal could be obtained within 15 min (at 2.6 g dry wt algae l −1 ); this result compares favorably to the 2.5 h or so required by the control culture. The unit uptake rate for nitrogen (N-NH 4 + ) had a tendency to increase with the algal concentration, whereas that of phosphorus (P-PO 4 3− ) showed the opposite relationship. Considering the results obtained, it appears that hyperconcentrated algal cultures have a high potential for the tertiary treatment of wastewaters; a significant reduction of pond surface for large scale operations can be anticipated.

Biotreatment of anaerobically digested swine manure with microalgae

Abstract Anaerobic treatment of swine manure generates effluents that must be further treated before their final discharge. The required tertiary treatment can be effected by growing microalgae on the anaerobic effluent. We tested the ability of three species (two Chlorophyceae, Chlorella sp. and Scenedesmus obliquus , and a cyanobacterium, Phormidium bohneri ) to exhaust inorganic nitrogen and orthophosphate and to produce biomasses from anaerobically digested swine manure obtained from a 5-m 3 farm digester. The effluent to be treated (COD: 7·7 g/liter; NNH 4 + : 3·3 g/liter; PPO 4 3− : 0·3 g/liter; pH: 8·0) was diluted with tap-water to final manure concentrations of 0·6-3·0%. Batch culture was carried out in 1-liter flasks for 12 days at 228 μE/m 2 s (L:D, 12:12), at 10 and 20°C, starting with inocula of 80 mg dry wt algae per liter. Semicontinuous cultures were also performed with P. bohneri (1·0% manure, dilution rate of 50% per 4 days, 20°C, 14 days). The results show that biomass production was good (up to 500–750 mg dry wt per liter after 12 days) for all three species at 20°C with productivities (mg dry wt per liter per day) averaging 31 for P. bohneri , 37 for Chlorella sp. and 53 for S. obliquus . Total NNH 4 + exhaustion was obtained at 20°C with all three species (2·0% manure) within 12 days; corresponding reduction of PPO 4 3− was over 90%, and COD abatement was 60–90%, depending on the species. Under natural conditions, the best candidate for batch treatment would appear to be Chlorella sp. Under semicontinuous conditions, P. bohneri , which can be easily harvested, is indeed interesting, with removal rates (10·4 mg NNH 4 + /g dry wt per day and 0·6 mg PPO 4 3− /g dry wt per day) similar to those obtained with Chlorella sp. grown in batch at similar manure concentrations.

Biotreatment of fish farm effluents using the cyanobacterium Phormidium bohneri

The potential environmental impact of effluent from fish farms is of increasing environmental concern. Although concentrations in total nitrogen and phosphorus are usually low, their impact on the environment cannot be ignored because of the high nutrient mass flows utilized during fish farming. In this paper we investigated the use of a non-toxic cyanobacterium, Phormidium bohneri, to remove dissolved inorganic nutrients from fish farm effluents. Wastewater was directed toward three completely mixed 70 1 photobioreactors with retention time of 8, 12 and 24 h, respectively. Average efficiencies of ammonia nitrogen removal from rainbow trout (Oncorhynchus mykiss) effluent was 82% and 85% for soluble orthophosphate, over a 1 month period. From these results, the potential use of P. bohneri as an alternative for the tertiary treatment of fish farm effluents is analyzed.