Initial Biomass Concentration Research Articles

Alkaline-assisted Microwave Pretreatment of Tetraselmis suecica Biomass for Fed-batch Enzymatic Hydrolysis

A two-part study on pretreatment and fed-batch enzymatic hydrolysis of pretreated Tetraselmis suecica using a high initial biomass concentration was conducted. First, the effect of different pretreatment processes, i.e. microwave (MC), dilute alkaline (AK), and microwave-alkaline assisted (MAK) pretreatment, on enzymatic hydrolysis of T. suecica biomass was evaluated. Furthermore, high initial biomass concentration enzymatic hydrolysis improvement via a fed-batch strategy was performed. Among the pretreatments tested, the MAK pretreatment produced the highest sugar concentration at 9.83 ± 0.24 mg/mL, corresponding to a conversion yield of up to 85.58% of carbohydrate content available in the pretreated biomass. The solid fraction generated after pretreatment was characterized using Fourier transform infrared (FTIR) spectroscopy. The FTIR analysis revealed a significant change in the functional hydroxyl and acetyl groups of the biomass, which is favorable for enzymatic hydrolysis. Introducing an initial microalgal biomass concentration beyond 15% (w/v) exhibited a low enzymatic hydrolysis yield. The fed-batch enzymatic hydrolysis strategy of the MAK pretreated T. suecica was further investigated by adding the substrate at different time intervals. The findings indicate that the fed-batch operation system could enhance sugar production and enzymatic hydrolysis yield one-fold.

Dihydroxyacetone production from glycerol using Gluconobacter oxydans: Study of medium composition and operational conditions in shaken flasks.

The production of dihydroxyacetone from glycerol employing aerobic cultures of Gluconobacter oxydans is studied. Dihydroxyacetone is one of the most important value-added products obtained from glycerol, a by-product of biodiesel production. The effect of organic nitrogen source and initial substrate concentrations has been studied together with the possibility of product inhibition. Afterward, the influence of the main operating conditions (temperature, shaking speed, and initial biomass concentration) on in vivo glycerol dehydrogenase activity has also been considered. The results show no evidence of glycerol inhibition, but an important product inhibition was detected, which has been taken into account in a kinetic model for enzymatic activity description. In terms of operating conditions, pH was found to exert a great impact on glycerol conversion, being necessary to keep it above 4 to ensure complete glycerol conversion. The minimum temperature that maximized enzymatic activity was found to be 30°C. In addition, a surprising decoupling between biomass concentration and dihydroxyacetone production rate was observed when adding increasing nitrogen source concentrations at a fixed shaking speed. Glycerol dehydrogenase activity remains constant despite the increase in biomass concentration, contrary to what would be expected. This fact revealed the existence of a rate limiting factor, identified subsequently as oxygen transfer rate depending on the biomass concentration.

Sources of anammox granular sludge and their sustainability in treating low-strength wastewater

Anaerobic ammonium oxidation (anammox) has been widely applied in the treatment of high-strength nitrogen wastewaters. However, few engineering practices were reported to treat low-strength nitrogen wastewaters. In this study, three types of anammox granular sludge (GS) were separately collected from the expanded granular sludge bed (EGSB) reactors treating nitrogen wastewaters at high (H-), moderate (M-) and low (L-) nitrogen loading rates (NLRs), and employed for the treatment of low-strength nitrogen wastewater in sequencing batch advanced nitrogen removal (ANR) systems. The ANR system with M-GS (namely M-ANR system) was most useful. At the initial biomass concentration of 2.43 g-VSS·L−1, cycle length of 8 h and influent total nitrogen (TN) concentration of less than 15 mg·L−1, the performance data were as follows: effluent TN of less than 1 mg·L−1, TN removal efficiency of more than 92.8%, the nitrogen removal rate (NRR) of 0.039 kg-N·m−3·d−1. The efficient performance lasted as long as 46 cycles, indicating the sustainability of the M-ANR system. The advanced microscopic analysis and metagenomic analysis were applied to reveal the successful but non-permanent treatment by the M-ANR system. The long-time lag between biomass decay and sludge activity decay provided a window period for the good performance of M-ANR system. However, the weak support of oligotrophic habitat for anaerobic ammonium oxidizing bacteria community was doomed to the degradation of anammox GS, resulting in gradual loss of their activities. A periodic addition of fresh M-GS or a periodic rejuvenation cultivation in the eutrophic habitat is necessary to achieve a permanent performance.

Role of hydrogen (H2) mass transfer in microbiological H2-threshold studies.

Gas-to-liquid mass transfer of hydrogen (H2) was investigated in a gas-liquid reactor with a continuous gas phase, a batch liquid phase, and liquid mixing regimes relevant to assessing kinetics of microbial H2 consumption. H2 transfer was quantified in real-time with a H2 microsensor for no mixing, moderate mixing [100 rotations per minute (rpm)], and rapid mixing (200rpm). The experimental results were simulated by mathematical models to find best-fit values of volumetric mass transfer coefficients-kLa-for H2, which were 1.6/day for no mixing, 7/day for 100rpm, and 30/day for 200rpm. Microbiological H2-consumption experiments were conducted with Methanobacterium bryantii M.o.H. to assess effects of H2 mass transfer on microbiological H2-threshold studies. The results illustrate that slow mixing reduced the gas-to-liquid H2 transfer rate, which fell behind the rate of microbiological H2 consumption in the liquid phase. As a result, the liquid-phase H2 concentration remained much lower than the liquid-phase H2 concentration that would be in equilibrium with the gas-phase H2 concentration. Direct measurements of the liquid-phase H2 concentration by an in situ probe demonstrated the problems associated with slow H2 transfer in past H2 threshold studies. The findings indicate that some of the previously reported H2-thresholds most likely were over-estimates due to slow gas-to-liquid H2 transfer. Essential requirements to conduct microbiological H2 threshold experiments are to have vigorous mixing, large gas-to-liquid volume, large interfacial area, and low initial biomass concentration.

Outdoor microalgae cultivation at different biomass concentrations — Assessment of different daily and seasonal light scenarios by modeling

An efficient microalgae outdoor cultivation is hindered by the fluctuation of the photon flux density (PFD) during one day and the natural day-night-rhythm. As the light intensity is not directly adjustable, the adjustment of biomass concentration is often used for the indirect distribution of available photons to an appropriate number of cells.For this study, repeated fed batch cultivations were conducted in 28 L flat panel airlift reactors in Stuttgart, Germany between August and October 2015. The influence of the initial biomass concentration (1.5–9 g L−1) on the productivity of Chlorella sorokiniana was investigated.Two models (basing on different underlying assumptions) were developed, which used the results of a previous laboratory study to explain the effects of different PFD courses on the productivity outdoors. Both models were validated by using the results of the outdoor cultivation. With the model based on the light yield, an adequate prediction of the productivity was achieved. This leads to an assessment of the outdoor process with paradigmatic courses of the PFD.The application of the model on recorded outdoor PFD courses proved that not only the amount of photons has an impact on the productivity, but also their distribution during the day. Longer photoperiods with lower maximum PFD values (summer) lead to a higher productivity compared to shorter photoperiods with higher maximum PFD values (spring/fall). Additionally, the biomass concentration should be at least as low as 1.5 g L−1; this leads on the one hand to an improved light yield, as there is less self-shading of the algae culture, on the other hand, there is less night biomass loss at lower biomass concentrations.

Biodegradation of Quinoline by Hydrogel Beads of Activated Sludge in the Air-Lift Bioreactor

Quinoline is a nitrogen heterocyclic compound (NHC) with a molecular formula of C9H7N. Microbial degradation of quinoline occurs under both aerobic and anaerobic conditions. In this study, the aerobic biodegradation of quinoline was investigated with activated sludge which was taken from a municipal sewage wastewater treatment plant in the air-lift bioreactor (ALBR).The activated sludge was entrapped in poly-vinyl-alcohol-calcium alginate (PVA-Ca alginate) hydrogel beads. The optimal conditions for microbial cells entrapment, such as Ca-alginate concentration, biomass concentration in the hydrogel bead and bead size, were determined with concerning to improve the quinoline degradation rate. Also, the initial quinoline concentration was determined. The optimum temperature and initial pH for quinoline degradation were 30°C and pH 7–8, respectively. During the biodegradation process, the culture broth became yellow and brown in turn, which indicated that several intermediates were generated. The results showed that the diversity of microbial cells improves and accelerates the quinoline biodegradation. The repeated use of the hydrogel beads for quinoline degradation was performed and the results revealed that the beads were active and intact up to 4 successive cycles without breakage or loss their stability in the continuous mode. Thus, (PVA-Ca alginate) hydrogel beads have great potential to be a matrix for the cell immobilization in quinoline biodegradation. The various initial concentrations of quinoline (50, 100, 250, and 500mg/L) were completely degraded in batch-mode experiments; under optimal conditions: PVA conc., 80%w/v; calcium alginate conc., 20%w/v; initial biomass concentration the hydrogel bead, 3mL / 10 mL of gel solution; and the hydrogel bead size, about 3mm in diameter, at different time intervals (4, 6, 10, and 14h), respectively.

Effect of Operating Conditions and Immobilization on Butanol Enhancement in an Extractive Fermentation Using Non-ionic Surfactant.

The present study was undertaken in order to investigate effect of diverse parameters such as fermentation media, pH, initial concentration of biomass, different surfactant concentrations, and immobilization on increasing butanol and total solvent production. Cheng's fermentation media was successfully tested and perceived to increase final solvents concentration. Controlled pH at 12th and 24th hours had negative effect on butanol enhancement; however, it resulted in more butyric acid production which remained accumulated. Ten percent (v/v) biomass was evaluated to increase final solvents concentration and hence butanol yield compared to 20% and 30% (v/v) of initial biomass concentrations. Effect of surfactant concentration (3-20%) was studied on butanol production. Six percent (v/v) L62 resulted in 49% higher final butanol concentration compared to control. Simultaneous immobilization and fermentation showed higher butanol production (16.8g/L with 6%) which was attributed to partial immobilization of biomass.

Technical and economic potential evaluation of the strain Escherichia coli MS04 in the ethanol production from glucose and xylose

Currently, the production of energy from fossil fuels is generating great pollution. For this reason, alternatives to these fuels that are less polluting, such as biofuels, have been sought. These can be produced from hydrolysates containing glucose and xylose. Metabolic engineered microorganisms are required to consume both sugars and to improve the feasibility of these processes. In this paper, the production of ethanol is evaluated using a medium that simulates a hydrolysate of corn stover (25 g/L xylose, 35 g/L glucose) with the metabolic engineered Escherichia coli strain MS04. The influence of the initial concentration of biomass on the production of ethanol was analyzed. With the experimental results, a technical and economic analysis of the entire process is performed with the Aspen Plus software. As a result, it is highlighted that the initial concentration of biomass only affects the fermentation time since, at a lower concentration, a longer fermentation time is required to reach a final ethanol concentration of 30 g/L. The scale of the process influences the distribution of costs is influenced by the scale of the process. On a larger scale, the raw materials represent the higher share and the depreciation on the smaller one. The use of a metabolic engineered strain allows the better use of the obtained hydrolysates from agroindustrial residues.

Platinum(II) reduction to platinum nanoparticles in anaerobic sludge.

To help mitigate future problems in the supply of platinum group metals (PGM) due to their scarcity and high demand, new recovery processes must be developed. Microbial processes are a great alternative for the recovery of PGM from waste since they are clean and environmentally friendly techniques. This research studied the microbial reduction of Pt(II) using an anaerobic granular sludge under different physiological conditions. The anaerobic granular sludge was able to reduce Pt(II) to Pt(0) nanoparticles that were deposited intracellularly as well as extracellularly as confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Hydrogen (H2) and formate supported the chemical reduction of Pt(II) while ethanol supported the biologically catalyzed reduction of Pt(II). Increasing initial concentrations of Pt(II), ethanol or biomass were each shown to increase the Pt(II) reduction rates. This study reported for the first time the reduction of Pt(II) using anaerobic granular sludge and provided insights that could help develop biorecovery techniques to alleviate future problems in the supply of PGMs.

Determination of optimal dose of allylthiourea (ATU) for the batch respirometric test of activated sludge.

Allylthiourea is a known specific inhibitor for ammonium oxidiser to suppress its oxygen uptake, and is commonly used for various kinds of batch respirometric tests to detect heterotrophic respiration in activated sludge. However, when high heterotrophs were present in the sample, it appeared the inhibitor was noticeably degraded and reached below the inhibition threshold after a couple of days, which resulted in overestimation of the heterotrophic respiration. The biological decomposition of the inhibitor was expressed with a Monod-type rate expression having a half-saturation coefficient of 980 mg-COD/L and maximum specific growth rate of 1.0 d-1. The developed kinetic model, including the growth and decay of the heterotrophs and nitrifiers, indicated that the ATU with about 90 mg-ATU/L which was initially dosed to the system would reach below the inhibition threshold of 1.0 mg-ATU/L after 10 days when 750 mg-COD/L of heterotrophs were present. From the kinetic model, an empirical formula to calculate a safe minimum ATU dose for the batch respirometric test was elaborated. The model also provided a modified experimental procedure to accurately estimate the initial heterotrophic biomass concentration in the sample and its specific decay rate based on IWA Activated Sludge Models.

Enhancement of hydrogen production rate by high biomass concentrations of Thermotoga neapolitana

The objective of this study was to enhance the hydrogen production rate of dark fermentation in batch operation. For the first time, the hyperthermophilic pure culture of Thermotoga neapolitana cf. Capnolactica was applied at elevated biomass concentrations. The increase of the initial biomass concentration from 0.46 to 1.74 g cell dry weight/L led to a general acceleration of the fermentation process, reducing the fermentation time of 5 g glucose/L down to 3 h with a lag phase of 0.4 h. The volumetric hydrogen production rate increased from 323 (±11) to 654 (±30) mL/L/h with a concomitant enhancement of the biomass growth and glucose consumption rate. The hydrogen yield of 2.45 (±0.09) mol H2/mol glucose, the hydrogen concentration of 68% in the produced gas and the composition of the end products in the digestate, i.e. 62.3 (±2.5)% acetic acid, 23.5 (±2.9)% lactic acid and 2.3 (±0.1)% alanine, remained unaffected at increasing biomass concentrations.

Studying the influence of design and operation mode parameters on efficiency of the systems of biochemical purification of emissions

A procedure for evaluating efficiency of the systems of biological elimination of soluble and insoluble in water harmful gaseous substances as well as dissolved in water contaminants has been devised. The procedure is based on previously developed mathematical models of the corresponding non-stationary bio oxidation processes. Based on the analysis of 27 design versions, real capabilities of biological purification facilities were shown, the effect of design and operation mode parameters on efficiency of the systems of biological destruction of methane, hydrogen sulfide and formaldehyde were assessed. In quantitative terms, the results obtained in numerical experiments indicate the necessity of taking into account variation of the rate of pollutant inflow in the process of vessel filling. It was established that an increase in the facility efficiency in terms of the volume of the gas-air mixture, N, causes a decrease in methane concentration at the bioreactor entry and a reduction of the purification degree to 62 %. An increase in the rate of hydrogen sulfide inflow to the reactor leads to a reduction of the purification degree from 98 to 95 %. An increase in the initial concentration of biomass by a factor of 1.7 causes a decrease in concentration of hydrogen sulfide in water from 2.5 to 1.1 g/m 3 . A significant decrease in the average specific bio oxidative power with an increase in the working space in which the final stage of emission purification from formaldehyde takes place was also observed. The revealed regularities represent a tool for improving quality of design solutions and increasing effectiveness of bio oxidation modes in operation of the systems of biological gas purification.

BIOCHEMICAL RESPONSES FROM BIOMASS OF ISOLATED Chlorella sp., UNDER DIFFERENT CULTIVATION MODES: NON-LINEAR MODELLING OF GROWTH KINETICS

Abstract In this study, the effect of different modes of cultivation viz., photoautotrophic (AT), heterotrophic (HT) and photomixotrophic (MT), on the growth and biochemical responses of Chlorella sp. isolated from local ponds. The performance of microalgal growth was quantified using nonlinear growth models such as Gompertz, logistic, Baranyi-Roberts, Morgan under different cultivation conditions. The results revealed that microalgae could grow better in MT than in other cultivation modes with a major increase in biochemical responses for carbohydrates, which showed higher accumulation under HT. The maximum biomass concentration was 1.24 g L-1 (MT), 1.16 g L-1 (HT), 0.76 g L-1 (AT) with maximum specific growth rates of 0.0083 h-1 (HT), 0.0078 h-1 (MT) and 0.0055 h-1 (AT) respectively. The biomass concentration was higher in the order of MT>HT>AT for which MT yielded 8.8 fold higher biomass, compared with the initial biomass concentration, at the end of experiments (16 days). Concomitant increases in biochemical responses were observed in the three cultivation conditions. Protein and lipid accumulation in the MT mode was higher (1.2 fold) compared with the initial protein yield as well as the other cultivation modes. However, the carbohydrate yield was higher (1.12 fold) in the heterotrophic mode than in other cultivation conditions.

Multi-objective optimization in biotechnological processes: application to plant cell suspension cultures of Thevetia peruviana

Bioprocesses productivity is a compromise between two conflicting objectives, maximization of biomass growth rate and minimization of substrate consumption. In this work, a model based multi-objective optimization problem is solved for improving the process productivity in plant cell suspension cultures of Thevetia peruviana. A solution of the multi-objective problem allowed determining the optimal initial concentrations of substrate and biomass for assuring maximal productivity. Model-based optimization is carried out using a mechanistic model, which includes a representation of the intracellular processes taking place on the plant cells. The best solutions were chosen from the Pareto front in agreement with expert criterion. Results indicate that an initial inoculum concentration of 3.91g/L and an initial sucrose concentration of 23.63g/L, are recommended as initial conditions for obtaining a biomass productivity of 1.57g/L*day with an acceptable sucrose uptake. Experimental validation of the optimal found was carried out and the productivity obtained was 1.52g/L using an initial inoculum concentration of 4.27g/L and an initial sucrose concentration of 25.44g/L. Results suggest that the proposed methodology can be extended to increase the productivity in terms of metabolite production from this plant cell cultures and other plant species.

Optimization of Chlorella sorokiniana cultivation condition for simultaneous enhanced biomass and lipid production via CO2 fixation

In this work, the cultivation condition of Chlorella sorokiniana was investigated to optimize biomass and lipid production. The influence of initial biomass content, nitrogen sources and concentration, phosphorus concentration, pH and CO2 concentration was tested. The experimental results indicated that 1.0g/L glycine could be a suitable nitrogen source for Chlorella sorokiniana. Meanwhile, KH2PO4 with the concentration of 11.4mg/L at the pH of 9 was preferable phosphorus source for biomass and lipid accumulation. The maximum lipid concentration and content could achieve 173.73mg/L and 44.1%. When CO2 was added as inorganic carbon source with the gas flow rate of 6sccm, the maximum biomass concentration was 1.0g/L on the fourth day.

Influence of spectral light quality on the pigment concentrations and biomass productivity of Arthrospira platensis

The species in the Arthrospira genus are cultured at a large scale throughout the world primarily for food supplements for human and animal diets. These species are valued for the rich composition of their biomass, which contains minerals, antioxidants, proteins and essential amino acids. This biomass can also be used for high-value product extraction, for example, the pigments chlorophyll a, β-carotene and phycocyanin as well as essential fatty acids. The use of LEDs is a solution for optimizing the productivity and biochemical composition of biomass produced by these microalgae. In this study, an innovative strategy for using LEDs was evaluated for Arthrospira platensis cultivation to increase its biomass productivity and high-value pigments (chlorophyll a, total carotenoids and phycocyanin). Microalgae suspensions were cultured in 250 mL Erlenmeyer flasks containing 120 mL of culture (George-modified Zarrouk's medium, pH 8.90) at 32 ± 1 °C with constant stirring and an initial biomass concentration of 0.03 g L−1. The biomass weights from ten lighting conditions consisting of blue and red LEDs of different compositions were evaluated in relation to the algal productivity and the chlorophyll a, total carotenoid and phycocyanin contents. The best results were obtained using LEDs that had a 70% red and 30% blue composition and a light intensity of 100 μE m−2 s−1, leading to an average biomass productivity of 0.148 g L−1d−1 and average concentrations of 21.35 μg mL−1, 5.45 μg mL−1 and 167.98 μg mL−1 of chlorophyll a, carotenoids and phycocyanin, respectively, in the given culture volume.

Aerobic biodegradation kinetics for 1,4-dioxane under metabolic and cometabolic conditions

Biodegradation of 1,4-dioxane has been studied extensively, however, there is insufficient information on the kinetic characteristics of cometabolism by propanotrophs and a lack of systematic comparisons to metabolic biodegradation. To fill in these gaps, experiments were performed with suspended growth cultures to determine 16 Monod kinetic coefficients that describe metabolic consumption of 1,4-dioxane by Pseudonocardia dioxanivorans CB1190 and cometabolism by the propanotrophic mixed culture ENV487 and the propanotroph Rhodococcus ruber ENV425. Maximum specific growth rates were highest for ENV425, followed by ENV487 and CB1190. Half saturation constants for 1,4-dioxane for the propanotrophs were one-half to one-quarter those for CB1190. Propane was preferentially degraded over 1,4-dioxane, but the reverse did not occur. A kinetic model was used to simulate batch biodegradation of 1,4-dioxane. Propanotrophs decreased 1,4-dioxane from 1000 to 1 μg/L in less time than CB1190 when the initial biomass concentration was 0.74 mg COD/L; metabolic biodegradation was favored at higher initial biomass concentrations and higher initial 1,4-dioxane concentrations. 1,4-Dioxane biodegradation was inhibited when oxygen was below 1.5 mg/L. The kinetic model provides a framework for comparing in situ biodegradation of 1,4-dioxane via bioaugmentation with cultures that use the contaminant as a growth substrate to those that achieve biodegradation via cometabolism.

Competitive biosorption of heavy metals from aqueous solutions onto Streptomyces rimosus

The aim of this study is the simultaneous biosorption of Cd+2 and Ni+2 on a dead biomass, Streptomyces rimosus pretreated with NaOH (0,1 M). Kinetic tests were carried out for the binary mixture (cadmium-nickel) during 6 hours contact time to ensure that balance was reached. The amounts adsorbed at equilibrium were 22.8 mg Ni2+/g and 9.86 mg Cd2+/g biomass, respectively. The biosorption depends mainly by some parameters, such as the pH, the initial concentration of metal and the initial concentration of biomass. The isotherm of adsorption according to two models, Langmuir and Freundlich, was carried out in our study. The results of the kinetics of adsorption show that the experimental values are well represented by the kinetic model of pseudo-second order. This enables us to determine the behavior of these adsorbents with respect to a real industrial effluent.

Improving the ecological relevance of aquatic bacterial communities in biodegradability screening assessments

Concentrating cells from aqueous samples is a common requirement for the enumeration of biomass, investigations of microbial diversity and detection of relatively rare organisms in the environment. Accurately representing the initial sampled environments in the concentrated cells is of particular importance when the subsequent analyses have tangible environmental, economic and societal consequences, as is the case with environmental exposure and risk assessment of chemicals. This study investigated the potential use of four different cell concentration methods: centrifugation, membrane filtration, tangential flow filtration and column colonisation. These methods were assessed against a series of scientific and practical criteria, including: similarity of concentrated community to initial environmental sample; cell concentration achieved; biodegradation test outcome; sample throughput; and capital and maintenance costs. All methods increased cell concentration by as little as 10-fold to as much as 1000-fold. DGGE and 454 pyrosequencing analysis showed concentrated communities to have >60% similarity to each other, and the initial sample. There was a general trend for a more reliable assessment of 4-nitrophenol biodegradation in 96-well plate biodegradation assays, with increasing cell concentration. Based on the selection criteria, it is recommended that there is not one concentration method fit for all purposes, rather, the appropriate method should be selected on a case-by-case basis. Membrane filtration would be the most suitable method for low sample volumes; the increased throughput capacity of tangential flow filtration renders it most suitable for large volumes; and centrifugation is most suitable for samples with high initial biomass concentrations. The poor similarity in microbial community composition of the column colonised samples compared to the initial samples, suggested a concentration basis; this combined with its low sample throughput precluded this approach for future concentration studies of planktonic bacterial samples.

Flocculation Effect of Alkaline Electrolyzed Water (AEW) on Harvesting of Marine Microalga Tetraselmis sp.

Microalgae hold promise as a renewable energy source for the production of biofuel, as they can convert light energy into chemical energy through photosynthesis. However, cost-efficient harvest of microalgae remains a major challenge to commercial-scale algal biofuel production. We first investigated the potential of electrolytic water as a flocculant for harvesting Tetraselmis sp. Alkaline electrolyzed water (AEW) is produced at the cathode through water electrolysis. It contains mineral ions such as Na+, K+, Ca2+, and Mg2+ that can act as flocculants. The flocculation activity with AEW was evaluated via culture density, AEW concentration, medium pH, settling time, and ionic strength analyses. The flocculation efficiency was 88.7% at 20% AEW (pH 8, 10 min) with a biomass concentration of 2 g/l. The initial biomass concentration and medium pH had significant influences on the flocculation activity of AEW. A viability test of flocculated microalgal cells was conducted using Evans blue stain, and the cells appeared intact. Furthermore, the growth rate of Tetraselmis sp. in recycled flocculation medium was similar to the growth rate in fresh F/2 medium. Our results suggested that AEW flocculation could be a very useful and affordable methodology for fresh biomass harvesting with environmentally friendly easy operation in part of the algal biofuel production process.