Neochloris oleoabundans Growth Evaluation Under Different Nitrogen:Phosphorus:Carbon Feeding Strategies.

Microalgae are photosynthetic microorganisms known for their variety of compounds that can be useful for food, feed, pharmaceuticals, and fuel industries. Microalgae production costs have been one of the major obstacles to large-scale commercial production. Therefore, several studies are still being performed aiming to increase biomass by developing novel photobioreactor design and microalgae cultivation techniques. This work's purpose is to increase Neochloris oleoabundans biomass. Different nutrient-feeding regimes were tested in N. oleoabundans cultivation in Erlenmeyer flasks and bench-scale tubular photobioreactor. In Erlenmeyer flasks, the best concentrations of nitrate and phosphate were 8.82 mM and 5.16 mM, respectively. In bench-scale tubular photobioreactor, NaNO3 proved to be the best nitrogen source, in comparison with (NH4)2SO4 and NH4NO3. Still in the photobioreator, the addition of nitrate by fed-batch process combined with automated system of CO2 feeding showed to be of utmost importance for insuring a high density of N. oleoabundans. The essential nutrients evaluated in this work play an important role on N. oleoabundans biomass accumulation, as well as the photobioreactor configuration and feeding regimes.

Simultaneous use of urea and potassium nitrate for Arthrospira (Spirulina) platensis cultivation.

Urea has been considered as a promising alternative nitrogen source for the cultivation of Arthrospira platensis if it is possible to avoid ammonia toxicity; however, this procedure can lead to periods of nitrogen shortage. This study shows that the addition of potassium nitrate, which acts as a nitrogen reservoir, to cultivations carried out with urea in a fed-batch process can increase the maximum cell concentration (X(m) ) and also cell productivity (P(X) ). Using response surface methodology, the model indicates that the estimated optimum X(m) can be achieved with 17.3 mM potassium nitrate and 8.9 mM urea. Under this condition an X(m) of 6077 ± 199 mg/L and a P(X) of 341.5 ± 19.1 mg L(-1) day(-1) were obtained.

Kinetic and growth parameters of Arthrospira (Spirulina) platensis cultivated in tubular photobioreactor under different cell circulation systems.

Arthrospira platensis was cultivated in tubular photobioreactor in order to evaluate growth and biomass production at variable photosynthetic photon flux density (PPFD = 60, 120, and 240 µmol photons m(-2)s(-1)) and employing three different systems for cell circulation, specifically an airlift, a motor-driven pumping and a pressurized system. The influence of these two independents variables on the maximum cell concentration (X(m)), cell productivity (P(x)), nitrogen-to-cell conversion factor (Y(X/N) ), photosynthetic efficiency (PE), and biomass composition (total lipids and proteins), taken as responses, was evaluated by analysis of variance. The statistical analysis revealed that the best combination of responses' mean values (X(m) = 4,055 mg L(-1), P(x) = 406 mg L(-1)day(-1), Y(X/N) = 5.07 mg mg(-1), total lipids = 8.94%, total proteins = 30.3%, PE = 2.04%) was obtained at PPFD = 120 µmol photons m(-2)s(-1); therefore, this light intensity should be considered as the most well-suited for A. platensis cultivation in this photobioreactor configuration. The airlift system did not exert any significant positive statistical influence on the responses, which suggests that this traditional cell circulation system could successfully be substituted by the others tested in this work.

LPS removal from an E. coli fermentation broth using aqueous two-phase micellar system.

In biotechnology, endotoxin (LPS) removal from recombinant proteins is a critical and challenging step in the preparation of injectable therapeutics, as endotoxin is a natural component of bacterial expression systems widely used to manufacture therapeutic proteins. The viability of large-scale industrial production of recombinant biomolecules of pharmaceutical interest significantly depends on the separation and purification techniques used. The aim of this work was to evaluate the use of aqueous two-phase micellar system (ATPMS) for endotoxin removal from preparations containing recombinant proteins of pharmaceutical interest, such as green fluorescent protein (GFPuv). Partition assays were carried out initially using pure LPS, and afterwards in the presence of E. coli cell lysate. The ATPMS technology proved to be effective in GFPuv recovery, preferentially into the micelle-poor phase (K(GFPuv) < 1.00), and LPS removal into the micelle-rich phase (%REM(LPS) > 98.00%). Therefore, this system can be exploited as the first step for purification in biotechnology processes for removal of higher LPS concentrations.

Kinetics and bioenergetics of Spirulina platensis cultivation by fed-batch addition of urea as nitrogen source.

The cyanobacterium Spirulina platensis was cultivated in bench-scale miniponds on bicarbonate/carbonate solutions using urea as nitrogen source. To minimize limitation and inhibition phenomena, urea was supplied semicontinuously using exponentially increasing feeding rates. The average growth rates obtained alternately varying the total mass of urea added per unit reactor volume (275 < mT < 725 mg/L) and the total feeding time (9 < tT < 15 d) clearly evidenced nitrogen limitation for mT< 500 mg/L and excess nitrogen inhibition above this threshold. The time behavior of the specific growth rate at variable urea feeding patterns allowed estimation of the time-dependent Gibbs energy dissipation for cell growth under the actual depletion conditions of fed-batch cultivations. Comparison of the yield of growth on Gibbs energy obtained using either urea or KNO3 pointed to the preference of S. platensis for the former nitrogen source, likely owing to more favorable bioenergetic conditions.