Reduction In Biomass Concentration Research Articles

Algal bloom inhibition through cobalt nano particles to control Oscillatoria growth in fresh water lakes

Cobalt nano particles (CoNPs) were synthesized and tested against microalgae isolated from fresh water cyanobacterial blooms by assessing the effects on growth rate, biomass concentration and biochemical parameters. Oscillatoria was identified as the predominant isolate from algal blooms and treated with varying concentrations (1, 2, 3, 4 and 5 mg L-1) of CoNPs. Steady decline in the growth rate of microalgae was observed at the end of 5 days indicating the toxicity of CoNPs on microalgal growth. At the end of cultivation period, 88% of reduction in biomass concentration of Microcystis and Oscillatoria were observed at 5 mg L-1 of CoNPs. Both protein and carbohydrate contents of the microalgae were reduced with increasing concentration of nano particles. Based on the findings, this study demonstrates the efficiency of cobalt nano particles (CoNPs) on inhibition of fresh water algal blooms thereby reducing the eutrophication problem.

Evaluation of Neochloris oleoabundans as sustainable source of oil-rich biomass

In microalgae biotechnology, several strategies have been used aiming to increase biomass productivity and oil content, for example, by exploring novel bioreactor design and cultivation techniques. In the present study, the influence of stressing agents (sodium thiosulphate, sodium chloride, and glycerol), under nitrogen starvation, were evaluated for lipid accumulation in Neochloris oleoabundans. Additionally, different light regimes and the use of LED were also evaluated. The results showed that sodium thiosulfate, glycerol, and sodium chloride addition resulted in a reduction in biomass concentration, but, at the same time, an increase in lipid content. 2.5 mM of sodium thiosulfate provided the highest percentage of lipid content up to 44.7%. In a tubular photobioreactor, despite the twofold increase in biomass concentration, there was a decrease in lipid content, compared with cultures in Erlenmeyer flasks. Also, the use of white LED in combination with traditional fluorescent lamp (12 h:12 h) could efficiently replace 24 h light with fluorescent lamp for producing oil-rich N. oleoabundans biomass.

Inhibition Effects of Cobalt Nano Particles Against Fresh Water Algal Blooms Caused by <i>Microcystis</i> and <i>Oscillatoria</i>

Cyanobacterial blooms deplete nutrients, reduce water clarity, exhaust carbon di oxide and produces secondary metabolites which negatively affect aquatic organisms and water quality. Control of algal blooms using metal nano particles is one effective method for the safety of water environment. Cobalt nano particles (CoNPs) were synthesized and tested against microalgae isolated from fresh water cyanobacterial blooms by assessing the effects on growth rate, biomass concentration, photosynthetic pigments concentration and antioxidant enzyme activity. <i>Microcystis</i> and <i>Oscillatoria</i> were identified as the predominant isolates from algal blooms and treated with varying concentrations (1, 2, 3, 4 and 5 mg·L^-1) of CoNPs. Steady decline in the growth rate of microalgae was observed at the end of 5 days indicating the toxicity of CoNPs on microalgal growth. At the end of cultivation period, 78% and 88% of reduction in biomass concentration of <i>Microcystis</i> and <i>Oscillatoria</i> were observed at 5 mg·L^-1 of CoNPs. The chlorophyll content was reduced from 1.53 to 0.24 mg·L^-1 in <i>Microcystis</i> and 1.63 to 0.29 mg·L^-1 in <i>Oscillatoria</i>. There was a 69.3% and 73.2% decrease in carotenoid content of <i>Microcystis</i> and <i>Oscillatoria</i> respectively. Both protein and carbohydrate contents of the microalgae were reduced with increasing concentration of nano particles. The decrease in Super oxide dismutase (SOD) activity with increased nanoparticle concentration reveals the formation of stress in the microalgae. The increasing GSH activity proved the effect of CoNPs on the activation of antioxidative enzymes to protect the cells. This study demonstrates the efficiency of cobalt nano particles (CoNPs) on inhibition of fresh water algal blooms thereby reducing the eutrophication problem.

Aeration energy requirements for lipid production by Scenedesmus sp. in airlift bioreactors

Microalgae have potential to yield various bioenergy products, including algal biodiesel. For algal energy production, the process energy input must be substantially lower than the product energy. Airlift photobioreactors provide controlled environments with good mixing and mass transfer; however, previous work reports a net energy ratio (NER; energy produced divided by energy consumed) less than 1. Here, the energy consumption in these reactors was improved by combined optimisation of superficial gas velocity and its CO2 concentration. Increasing CO2 concentration resulted in increased tolerance to lower superficial gas velocities, down to a critical minimum value. A 75% reduction in aeration power input was obtained by reducing superficial gas velocity from 0.0210 to 0.0052ms−1 at 5 400ppm CO2, without substantial reduction in biomass concentration (2.27 to 1.93gL−1, respectively) or productivity (0.189 to 0.173gL−1d−1, respectively). The NER under these conditions was 5.47 for biomass plus lipid and 1.01 for lipid only. The CO2 supply rate, product of superficial gas velocity and CO2 concentration, correlated with the CO2 transfer rate which influenced algal productivity. The range of NERs measured across the superficial gas velocities studied indicates the ability to optimise algal cultivation in photobioreactors for the improved feasibility of algal bioenergy.

Influence of temperature on the partial nitritation of reject water in a Granular Sequencing Batch Reactor

Two Granular Sequencing Batch Reactors were operated to perform partial nitrification of sludge reject water at different temperatures, from 25–41°C. Every temperature was fixed for about a month in order to evaluate the nitritation rate, morphological features of aggregates and bacterial populations. The optimum temperature was found between 33 and 37°C in terms of nitritation rate. Morphological features of granules did not show significant changes with temperature in the range between 28 and 37°C; Feret diameter remained at 5.8±0.7 mm and roundness was 0.76±0.02. Lower temperatures promoted the appearance of filamentous bacteria, leading to an increase of the sludge volume index (SVI) and a consequent reduction of biomass concentration. When the temperature was increased to 39°C, more than the 80% of aggregates showed a diameter higher than 6 mm but density decreased from 28 to 19 g VSS L−1, resulting in an increase of the SVI from 33 to 80 mL g−1. The establishment of 41°C caused a rapid destabilization of the system and nitritation activity disappeared. Bacterial populations did not experience significant changes during the experimental period and Nitrosomonas was the dominant species at all the temperatures assayed.

Possible synergistic effect between high lactate and insufficient intake of peptides caused biomass reduction during high-cell starter culture production

Lactic starter culture production is normally subjected to the end-product inhibition on growth, which limits the biomass produced per production batch. Removal of lactate ions during the biomass production has improved the biomass production. It allows for the use of higher sugar concentration so that high biomass concentration can be obtained. Lactate removal by ion exchange resin during Lactococcus lactis NZ133 cultivation was applied as a strategy for enhancing the production of lactic starter culture biomass. At high lactose concentrations of 180 g/l, the unexpected reduction in the biomass was evident regardless of the remaining sugar in the fermentation broth. The amount of protein and proteins/polypeptides pattern profile during cultivation were investigated as protein availability was suspected to be the potential cause of biomass reduction during high cell cultivation applying the ion exchange technique. Reduction in biomass concentration, after its maximum of 26 g/l, was observed after the protein concentration was unchanged while the remaining lactose continued to be utilised. A sharp decrease in protein concentration following the addition of resin corresponded to the disappearance of the smear band of protein sized 6,512-26,625 Da when more resin was added to remove lactate. The smear band remained throughout the conventional batch cultivation period. Based on the results, insufficient supply of peptides caused by the loss through adsorption onto ion exchange resin which occurred at high lactate level was postulated as the most probable cause of the biomass reduction. The result also indicated an inefficient use of supplemented protein sources supplied in correspond to the increase in lactose concentration due to the presence of appreciable amounts of residual protein at the end of cultivation process.

Kinetics and modeling of the stereoselective reduction of acetoacetic acid esters by continuously growing cultures of Saccharomyces cerevisiae

Pseudostationary experiments (chemostat cultures) revealed a decrease of D R with increasing concentration of starting material. This is interpreted as an inhibition of respiration by the starting material resulting also in a reduction of biomass concentration: glucose uptake was not affected. The products did not show any inhibitory effect. At all dilution rates > D R no reasonable steady states could be established (washout of the cultures) and the rates of reduction were negligible, as they were also in transient experiments. Maximal values of the volumetric product formation rate were approximately 1 g l −1 h −1 and found at dilution rates close to D R: obviously, the product formation is growth associated. During pulse experiments values between 1 and 2 g l −1 h −1 were measured. Product formation was found to depend strictly on oxidative glucose metabolism. A pseudomechanistic model is proposed considering regulatory effects and product formation: its sensitive parameters were estimated off- and on-line.