Biosorption Performance of Multimetal Resistant Fungus Penicillium chrysogenum XJ-1 for Removal of Cu2+ and Cr6+ from Aqueous Solutions

Adsorption for heavy metals via biomaterials such as fungal biomass presents a practical remediation technique for polluted water. Among all known filamentous fungi, Penicillium chrysogenum is widespread in nature and can serve as a biosorbent for heavy metals. In the current study, the ability of P. chrysogenum XJ-1 to remove copper (Cu²⁺) and chromium (Cr⁶⁺) from water was evaluated. The maximum biosorption capacity of XJ-1 for Cu²⁺ reached 42.83 ± 0.57 mg g^?1 dry biomass at pH 5.0 after the equilibrium time of 1.5 h. The maximum biosorption capacity for Cr⁶⁺ at pH 3.0 reached 52.69 ± 1.68 mg g^?1 dry biomass after the equilibrium time of 1.5 h. The biosorption data of XJ-1 biomass were well fitted to the Freundlich isotherm model and the pseudo-second-order Lagergren kinetic model. Laundry powder-treated and HCl-treated XJ-1 biomass significantly enhanced its adsorption capacity to Cu²⁺ and Cr⁶⁺, respectively. HCl and NaOH were suitable desorbents for Cu²⁺/Cr⁶⁺ loading biomass, respectively. Fourier transform infrared spectroscopy analyses revealed that hydroxyl, amine, and sulfonyl groups on the biosorbent contributed to binding Cu²⁺ and Cr⁶⁺ and that carbonyl and carboxyl groups were also vital binding sites of Cu²⁺. Scanning electron microscopy and energy-dispersive x-ray (SEM-EDX) analyses confirmed that considerable amounts of metals were precipitated on the cell surface of XJ-1. Our results suggested that XJ-1 might be used to purify multimetal-contaminated water. This low-cost and eco-friendly biomass of XJ-1 seems to have a broad use in the restoration of metal-contaminated water.     

Biosorption of Heavy Metals (Cd2+, Cu2+, Co2+, and Mn2+) by Thermophilic Bacteria,Geobacillus thermantarcticus and Anoxybacillus amylolyticus: Equilibrium and Kinetic Studies

ABSTRACT

Two strains of thermophilic bacteria, Geobacillus thermantarcticus and Anoxybacillus amylolyticus, were employed to investigate the biosorption of heavy metals including Cd²⁺, Cu²⁺, Co²⁺, and Mn²⁺ ions. The effects of different biosorption parameters such as pH (2.0–10.0), initial metal concentrations (10.0–300.0 mg L^?1), amount of biomass (0.25–10 g L^?1), temperature (30–80°C), and contact time (15–120 min) were investigated. Concentrations of metal ions were determined by using an inductively coupled plasma optical emission spectrometry (ICP-OES). Optimum pHs for Cd²⁺, Cu²⁺, Co²⁺, and Mn²⁺ biosorption by Geobacillus thermantarcticus were found to be 4.0, 4.0, 5.0, and 6.0, respectively. For Anoxybacillus amylolyticus, the optimum pHs for Cd²⁺, Cu²⁺, Co²⁺, and Mn²⁺ biosorption were found to be 5.0, 4.0, 5.0, and 6.0, respectively. The Cd²⁺, Cu²⁺, Co²⁺, and Mn²⁺ removals at 50 mg L^?1 in 60 min by 50 mg dried cells of Geobacillus thermantarcticus were 85.4%, 46.3%, 43.6%, and 65.1%, respectively, whereas 74.1%, 39.8%, 35.1%, and 36.6%, respectively, for Anoxybacillus amylolyticus. The optimum temperatures for heavy metal biosorption were near the optimum growth temperatures for both strains. Scatchard plot analysis was employed to obtain more compact information about the interaction between metal ions and biosorbents. The plot results were further studied to determine if they fit Langmuir and Freundlich models.     

Cr6+ bioremediation efficiency of Oscillatoria laete-virens (Crouan & Crouan) Gomont and Oscillatoria trichoides Szafer: kinetics and equilibrium study

Two species of cyanobacteria, Oscillatoria laete-virens (Crouan & Crouan) Gomont and Oscillatoria trichoides Szafer, were isolated from a polluted environment and studied for their Cr⁶⁺ removal efficiency from aqueous solutions. The parameters studied included the solution pH, contact time, initial concentration of Cr⁶⁺ and culture density. Living biomass is more efficient than dead biomass in Cr⁶⁺ removal. Removal by living biomass involves bioreduction and biosorption. Below pH 3.1, bioreduction is favored and biosorption is dominant at higher pH. The highest removal through biosorption for living biomass was achieved between pH 5 and 5.9 and for dead biomass at pH 2. The maximum removal was on the tenth day of exposure for both the species. Cr⁶⁺ removal increased from 0.2 to 0.4 g L^?1 of culture biomass with a decrease with further increase in biomass. Increased Cr⁶⁺ concentration decreases growth of both the species over time. Both species tolerate a concentration as high as 30 mg L^?1 Cr⁶⁺. There was no evidence of bioreduction in the case of dead biomass. Living biomass of O. laete-virens followed both Langmuir and Freundlich models with maximum sorptive capacity (q _max) of 21.88 mg g^?1. The results of dead biomass were well fitted only to Langmuir isotherm. O. trichoides living biomass did not follow either of the isotherms, but removed the metal to a maximum extent of 38.7mg g^?1. The removal was better described by Freundlich isotherm in case of dead biomass. The pseudo-first-order model describes the kinetics better than the pseudo-second-order model in the case of living biomass. Participation of carboxylic, carbonyl, and amino groups in Cr⁶⁺ removal was confirmed by FTIR analysis. Both species seem to be promising biosorbents for Cr⁶⁺.     

Fermentation waste of Aspergillus terreus: a potential copper biosorbent

Aspergillus terreus mycelial waste produced during lipase production showed good copper biosorption capacity (160–180 mg Cu²⁺ biosorbed/g dry biomass). The sorption process followed fast kinetics and the absorption behaviour could be explained by a Freundlich isotherm model. The process was temperature independent and unaffected by the presence of many competing ions in a multi-ion situation. Maximum biosorption occurred between pH 4 and 5. The biomass could efficiently remove copper from mine effluents. Moreover the loaded biomass could easily be desorbed by a simple acid wash and could be reused a number of times without a decline in its biosorbing potential, thus making the process cost-effective.     

Influence of Cu2+ on the Amino Acids Profile of Saccharomyces cerevisiae RD1 during Growth

The growth and the amino acid composition of the strain Saccharomyces cerevisiae RD1 were studied in the presence of copper ions. The accumulation of biomass was inhibited with the increase of Cu²⁺ concentration. It should be noted that the synthesis of aromatic amino acids was promoted at lower Cu²⁺ concentration (100 mg·L^?1), but at higher concentrations the inhibiting effect was significant. The decreases of the amino acid contents with the increase of Cu²⁺ concentration varied upon their type. The total amount of amino acids was much lower at 300 and 400 mg·L^?1 Cu²⁺.     

Cu2+ Removal and recovery by Spi SORB: batch stirred and up-flow packed bed columnar reactor systems

The biosorption of Cu²⁺ by free and poly acrylamide gel (PAG) immobilized Spirulina platensis (SpiSORB) was characterized under batch and continuous packed bed columnar reaction systems. The biosorption of Cu²⁺ was shown to be highest at pH of 6.0 for both types of biomass. The PAG immobilization process did not interfere with the Cu²⁺ binding sites present on biomass leading to cent percent (ca. 250 mg g⁻¹ of dry biomass) retention of biosorption as compared to free cells. Transmission electron microscopy on Cu²⁺ localization revealed that majority of metal is being sequestered by the cell wall only. The infrared spectrum of metal treated S. platensis biomass indicated the possible involvement of amide, amino, and carboxyl groups in metal binding. Up-flow packed bed columnar reactor containing 2.0 g of PAG immobilized S. platensis shown a maximum of 143-fold volume reduction factor at the residence time of 4.6 min for Cu²⁺ alone and found to decrease dramatically when Zn²⁺ is present in a bimetallic solution.     

Multi-metal biosorption and bioaccumulation by Exiguobacterium sp. ZM-2

The present work deals with the biosorption performance of dried and non-growing biomasses of Exiguobacterium sp. ZM-2, isolated from soil contaminated with tannery effluents, for the removal of Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ from aqueous solution. The metal concentrations studied were 25 mg/l, 50 mg/l, 100 mg/l, 150 mg/l and 200 mg/l. The effect of solution pH and contact time was also studied. The biosorption capacity was significantly altered by pH of the solution. The removal of metal ions was conspicuously rapid; most of the total sorption occurred within 30 min. The sorption data have been analyzed and fitted to the Langmuir and Freundlich isotherm models. The highest Q_max value was found for the biosorption of Cd²⁺ at 43.5 mg/g in the presence of the non-growing biomass. Recovery of metals (Cd²⁺, Zn²⁺, Cu²⁺ and Ni²⁺) was found to be better when dried biomass was used in comparison to non-growing biomass. Metal removal through bioaccumulation was determined by growing the bacterial strain in nutrient broth amended with different concentrations of metal ions. This multi-metal resistant isolate could be employed for the removal of heavy metals from spent industrial effluents before discharging them into the environment.     

DETERMINATION OF METHYLENE BLUE BIOSORPTION BY Rhizopus arrhizus IN THE PRESENCE OF SURFACTANTS WITH DIFFERENT CHEMICAL STRUCTURES

Methylene blue (MB) biosorption properties of Rhizopus arrhizus were investigated in the presence of surfactants. The effects of cationic and anionic surfactants on MB removal by dead biomass (1 g L^?1) were determined. MB removal was tested as a function of initial pH (2–12), contact time (5–1440 min), and dye (37.4–944.7 mg L^?1) and surfactant (0–10 mM) concentrations. The opposite charged anionic surfactant dodecylbenzenesulfonic acid sodium salt (DBS) enhanced sorption of cationic MB by biomass dramatically. Maximum biosorption capacity was 471.5 mg g^?1 at pH 8 with 0.5 mM DBS at 944.7 mg L^?1 MB concentration. The surfactant-stimulated fungal decolorization method may provide a highly efficient, inexpensive, and time-saving procedure in biological wastewater treatment technologies.     

Isolation of highly copper‐tolerant fungi from the smelter of the Naganobori copper mine,an historic mine in Japan

Aims: Copper is a critical metal of modern industry, and is the most widespread heavy metal contaminant in wastewater. Therefore, isolation of copper‐tolerant microbes having the potential as biosorbent is fascinating not only from an environmental microbiology, but also from a biotechnology view point. In this study, we attempted to isolate highly copper‐tolerant microbes from soil samples of the Nabanobori copper mine, the oldest mine in Japan. Methods and Results: As a result of an enrichment culture, two fungal strains were isolated from soil of the smelter remains. The isolates could grow in a maximum of 200 mmol l^?l Cu²⁺, and grew under a wide pH range. The Cu²⁺‐binding capacity of nontreated biomass of the isolates was around 35 mg Cu²⁺ g^?1‐biomass. Analysis of 18S rDNA suggested that the isolates belong to the Aspergillus/Penicillium clade, but they represented a distinct lineage against known neighbours. Conclusion: The isolates were highly copper‐tolerant, and their Cu²⁺‐binding capacity was comparable to well‐studied fungal sorbents. The isolates were implied as novel species. Soil of the historic old mine under weather‐beaten conditions might be a suitable source for metal‐tolerant microbes. Significance and Impact of the Study: The present results advance our understanding of metal‐tolerant microbes, and offer a new tool for both environmental control and metal recovery operations.     

Characterization of cadmium removal by Rhodotorula sp. Y11

Experiments were conducted studying the removal of Cd²⁺ from water via biosorption using Rhodotorula sp. Y11. The effects of temperature and initial pH of the solution on biosorption were studied. Caustic and heat treatments showed different influences on the biosorption capacity, and the highest metal uptake value (19.38 mg g⁻¹) was obtained by boiling treated yeast cells. The presence of competing cations, such as Ag⁺, Cu²⁺, and Mg²⁺, except Na⁺ ions, significantly interfered with the metal uptake. Results indicate that the Langmuir model gave a better fit to the experimental data than the Freundlich equation. The q ₁₀ value was 11.38 mg g⁻¹ for Cd²⁺ uptake by Y11. Chemical modifications of the biomass demonstrated that carboxyl and amide groups play an important role in Cd²⁺ biosorption.     

Fixed-bed biosorption of Cu2+ by polyacrylonitrile-immobilized dead cells of Saccharomyces cerevisiae

Dead cells of Saccharomyces cerevisiae 54 were immobilized by entrappment in polyacrylonitrile. The beads obtained were used to adsorb copper in an up-flow fixed-bed column. The effect of polymer content and cell loading were studied to optimize the porosity and the efficiency in copper removal of the biosorbent beads in a batch system. The optimal concentration of the polyacrylonitrile was assumed to be 12%(w/v) and a concentration of 0.5 g cell dry weight in 1 g polymer was most effective in adsorption of Cu²⁺. The adsorption capacity of this biosorbent was 27 mg Cu²⁺/g dry biomass at 200 mg/l initial concentration of copper ions. Adsorption of Cu²⁺ in a batch system was studied using different initial concentrations of the solute. The optimal conditions in the up-flow column of the following parameters were determined: flow rate, bed height, and initial concentration of Cu²⁺ of the solutions. Results of fixed-bed biosorption showed that breakthrough and saturation time appeared to increase with the bed height, but decrease with the flow rate and the initial concentration. The linearized form of the Thomas equation was used to describe dynamic adsorption of metal ions. As a result, the adsorption capacity of the batch system and the column system was compared. Desorption of copper ions was achieved by washing the column biomass with 0.1 M HCl at an eluent flow rate of 1 ml/min. The reusability of the immobilized biomass was tested in five consecutive adsorption-desorption cycles. The regenerated beads retained over 45% of their original adsorption capacity after five A/D cycles. This revised version was published online in August 2006 with corrections to the Cover Date.     

pH effects on the removal of Cu2+, Cd2+ and Pb2+ from aqueous solution by waste brewery biomass

An industrial strain of Saccharomyces cerevisiae collected from the waste of a brewing industry was used to remove lead, cadmium and copper from aqueous solutions (1?mm). Metal removal efficiency by using either biomass suspension directly diluted into the metal solutions or biomass previously incubated and washed in distilled water was compared. In all experiments with unwashed biomass a shift in the medium pH from 4.5 to a final value in the 7.0–8.0 range occurred. This pH increase was responsible for a metal precipitation effect associated to the metal biosorption. A very different pH profile was observed when washed biomass was used leading to different removal profiles for Cd²⁺ and Pb²⁺ and a similar one for Cu²⁺. In the absence of biomass, medium components and/or the excreted intracellular products proved to interfere in the metal removal and to be responsible for 80% Pb²⁺ precipitation, in the pH 4.5–5.0 range. To initial metal solution pH, leading to the lowest residual ion concentrations, after 96?h of contact with unwashed biomass and in the absence of pH adjustment, was 4.5–5.0. Continuous or stepwise adjustment of medium pH to this range during the process was unfavourable for metal removal, being the continuous adjustment the worst procedure. In this case, Cd²⁺ was not biosorbed and Cu²⁺ removal decreased from 76 to 33%. However, Pb²⁺ was always extensively removed (89%) and only slightly affected by pH control. The global results suggest different removal mechanisms for each cation. Cu²⁺ was removed by both metal sorption and precipitation, due to the pH shift that occurred during the process, while Cd²⁺ removal showed to be completely dependent of this pH shift. Pb²⁺ was totally and quickly removed, by precipitation, in the presence of the biomass suspension and at pH 4.5. Moreover, the biosorbent changes occurring during the process played an important role in the metal removal when non-viable microbial biomass is used.     

Waste water treatment and metal (Pb<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>) removal by microalgal based stabilization pond system

A case study was undertaken for the treatment of domestic wastewater generated at village of Sanghol, Distt. Fatehgarh Sahib, Punjab (India), using a schematic designed algal and duckweed based stabilization pond system, which is discussed here for winter months only (November to March) as there was no growth of duckweeds and only algae dominated the whole system. A proficient increase in pH and dissolved oxygen was observed after the treatment with reduction in chemical oxygen demand and biochemical oxygen demand by 93% and 79% respectively. Chlorella sp. was the dominating algal species in the stabilization pond water during entire period and was studied for its Zn²⁺ and Pb²⁺ metal removal efficiency. 60–70% removal of Zn²⁺ was observed from culture medium containing 5–20 mg L^?1 Zn²⁺, which declined to 42% at 50 mg L^?1. A constant decline in cell number from 538 × 10⁵ to 8 × 10⁵ cells ml^?1 was observed indicating zinc toxicity to Chlorella. Lead was maximally removed by 66.3% from culture medium containing 1 mg L^?1. The lead removal efficiency was 45 50 % at higher 5 to 20 mg L^?1 of external lead concentrations. The increase in cell number indicated no signs of Pb²⁺ toxicity up to 20 mg L^?1. The maximum uptake (q _max) by live Chlorella biomass for both Zn²⁺ and Pb²⁺ was 34.4 and 41.8 mg/g respectively.     

COPPER TOLERANCE OF CHLAMYDOMONAS ACIDOPHILA (CHLOROPHYCEAE) ISOLATED FROM ACIDIC,COPPER-CONTAMINATED SOILS1

Cells of Chlamydomonas acidophila Negoro, isolated from three soils with different available copper contents (74, 80, and 87 μg·g^?1), were assayed for their responses to copper. Soil pH ranged from 3.3–3.9. Responses were evaluated using algistatic assays involving five day exposure to copper concentrations from 0.1–100 mg·L^?1 at pH 3.8 and 6.6 in defined liquid media. Interspecies and intraspecies comparisons were made between the soil isolates and laboratory strains of C. reinhardtii and C. acidophila, respectively. Algistatic copper concentrations of soil isolates were 20–125 times greater than those of the laboratory strain of C. reinhardtii. Concentrations of 0.1 mg Cu·L^?1, or greater, killed the laboratory strain of C. acidophila. Soil isolates of C. acidophila appeared to be copper tolerant; however, there was no conclusive evidence to indicate that the level of copper tolerance in the soil isolates was positively correlated with the level of available copper in the soil.     

EFFECT OF COPPER ON ALGAL COMMUNITIES FROM OLIGOTROPHIC CALCAREOUS STREAMS1

Two sets of experiments were done to quantify the effects of chronic copper exposure on natural peri‐ phyton in a nonpolluted calcareous river. The results of short‐term (up to 6 h exposure) experiments corroborated the significance of pH on copper toxicity. Copper toxicity increased when pH was reduced from 8.6 to 7.7, and this was related to the effect of pH on copper speciation (free copper concentration increased from 0.2% to 2.3% of total copper). Longer term experiments demonstrated that periphyton communities exposed to copper under pH variation (8.2–8.6) were already affected at 10 μg·L ^{? 1} (20–80 ng·L ^{? 1} Cu^{2 +} ) after 12 days of exposure. Copper exposure caused stronger effects on structural (algal biomass and community structure) than on functional (photosynthetic efficiency) parameters of peri‐ phyton. Changes in community composition included the enhancement of some taxa (Gomphonema gracile), the inhibition of others (Fragilaria capucina and Phormidium sp.), and the appearance of filament malformations (Mougeotia sp.). The results of our study demonstrated that several weeks of exposure to copper (10–20 μg·L ^{? 1}) were sufficient to cause chronic changes in the periphyton of oligotrophic calcareous rivers. This degree of copper pollution can be commonly found in the Mediterranean region as a result of agricultural practices and farming activities.     

Biosorption of heavy metal ions by brown seaweeds from southern coast of Korea

Heavy metal ions (Pb²⁺, Cd²⁺, Mn²⁺, Cu²⁺, and Cr₂O₇ ^2?) were biosorbed by brown seaweeds (Hizikia fusiformis, Laminaria japonica, and Undaria pinnatifida) collected from the southern coast of South Korea. The biosorption of heavy metal ions was pH-dependent showing a minimum absorption at pH 2 and a maximum biosorption at pH 4 (Pb²⁺, Cd²⁺, Mn²⁺, and Cr₂O₇ ^2?) or pH 6 (Cu²⁺). Biosorption increased most noticeably for pH changes from 2 to 3. In the latter pH range, biosorption increased, because a higher pH decreased the electrostatic repulsion between metal ions and functional groups on the seaweed. In the pH range of 2 ～ 4, biosorption of negatively-charged chromium species (Cr₂O₇ ^?2) followed the pattern of positively-charged metal ions (Pb²⁺, Cd²⁺, Mn²⁺, and Cu²⁺). This suggests that the most prevalent chromium species were positively-charged Cr³⁺, reduced from Cr⁶⁺ in Cr₂O₇ ^?2. Whereas positively-charged heavy metal ions (Pb²⁺, Cd²⁺, Mn²⁺, and Cu²⁺) reached a plateau after the maximum level, biosorption of chromium ions decreased noticeably between pH 5 and 8. Kinetic data showed that biosorption by brown seaweed occurred rapidly during the first 10 min, and most of the heavy metals were bound to the seaweed within 30 min. Equilibrium adsorption data for a lead ion could fit well in the Langmuir and Freundlich isotherm models with regression coefficients (R ²) between 0.93 and 0.98.     

Biosorption of copper(II) from aqueous solutions by green alga <Emphasis Type="Italic">Cladophora fascicularis</Emphasis>

Biosorption is an effective means of removal of heavy metals from wastewater. In this work the biosorption behavior of Cladophora fascicularis was investigated as a function of pH, amount of biosorbent, initial Cu²⁺ concentration, temperature, and co-existing ions. Adsorption equilibria were well described by Langmuir isotherm models. The enthalpy change for the biosorption process was found to be 6.86 kJ mol⁻¹ by use of the Langmuir constant b. The biosorption process was found to be rapid in the first 30 min. The presence of co-existing cations such as Na⁺, K⁺, Mg²⁺, and Ca²⁺ and anions such as chloride, nitrate, sulfate, and acetate did not significantly affect uptake of Cu²⁺ whereas EDTA substantially affected adsorption of the metal. When experiments were performed with different desorbents the results indicated that EDTA was an efficient desorbent for the recovery of Cu²⁺ from biomass. IR spectral analysis suggested amido or hydroxy, C=O, and C–O could combine strongly with Cu²⁺.     

Zn2+ biosorption by Oscillatoria anguistissima

Oscillatoria anguistissima showed a very high capacity for Zn²⁺ biosorption (641 mg g⁻¹ dry biomass at a residual concentration of 129·2 ppm) from solution and was comparable to the commmercial ion-exchange resin IRA-400C. Zn²⁺ biosorption was rapid, pH dependent and temperature independent phenomenon. Zn²⁺ adsorption followed both Langmuir and Freundlich models. The specific uptake (mg g⁻¹ dry biomass) of metal decreased with increase in biomass concentration. Pretreatment of biomass did not significantly affect the biosorption capacity of O. anguistissima. The biosorption of zinc by O. anguistissima was an ion-exchange phenomenon as a large concentration of magnesium ions were released during zinc adsorption. The zinc bound to the biomass could be effectively stripped using EDTA (10 mM) and the biomass was effectively used for multiple sorption–desorption cycles with in-between charging of the biomass with tap water washings. The native biomass could also efficiently remove zinc from effluents obtained from Indian mining industries.     

Response Surface Modeling for Co-Remediation of Cr6+ and Pentachlorophenol by Bacillus cereus RMLAU1: Bioreactor Trial and Structural and Functional Characterization by SEM-EDS and FT-IR Analyses

This is the first report on optimization of process variables for simultaneous bioremediation of pentachlorophenol (PCP) and Cr⁶⁺ employing traditional and response surface methodology (RSM). In a one-factor-at-a-time approach, the effect of PCP level exhibited maximum bacterial growth and Cr⁶⁺ (82%) and PCP (91.5%) removal at initial 100 mg PCP L^?1 with simultaneous presence of 200 mg Cr⁶⁺ L^?1 within a 36-h incubation. However, at varied Cr⁶⁺ concentrations, maximum growth and Cr⁶⁺ (97%) and higher PCP (59%) removal were achieved at 50 mg Cr⁶⁺ L^?1 with simultaneous presence of 500 mg PCP L^?1 within a 36-h incubation. The Box-Behnken design suggested 100% Cr⁶⁺ and 95% PCP remediation at 36 h under optimum conditions of 75?mg PCP and 160 mg Cr⁶⁺ L^?1, pH 7.0, and 35°C; Cr⁶⁺ removal was further enhanced to 97% in bioreactor trial. Fourier transform infrared (FT-IR) analysis revealed the likely involvement of hydroxyl, amide, and phosphate groups in Cr³⁺ binding. Scanning electron microscopy and energy-dispersive x-ray spectroscopy (SEM-EDS) showed biosorption of reduced chromium on bacterial cell surface. This isolate can be employed for eco-friendly and effective in situ bioremediation of Cr⁶⁺ and PCP simultaneously.     

Inorganic carbon and pH effect on growth and lipid productivity of Tetraselmis suecica and Chlorella sp (Chlorophyta) grown outdoors in bag photobioreactors

There has been considerable interest in cultivation of green microalgae (Chlorophyta) as a source of lipid that can alternatively be converted to biodiesel. However, almost all mass cultures of algae are carbon-limited. Therefore, to reach a high biomass and oil productivities, the ideal selected microalgae will most likely need a source of inorganic carbon. Here, growth and lipid productivities of Tetraselmis suecica CS-187 and Chlorella sp were tested under various ranges of pH and different sources of inorganic carbon (untreated flue gas from coal-fired power plant, pure industrial CO₂, pH-adjusted using HCl and sodium bicarbonate). Biomass and lipid productivities were highest at pH 7.5 (320?±?29.9 mg biomass L^?1 day^?1and 92?±?13.1 mg lipid L^?1 day^?1) and pH 7 (407?±?5.5 mg biomass L^?1 day^?1 and 99?±?17.2 mg lipid L^?1 day^?1) for T. suecica CS-187 and Chlorella sp, respectively. In general, biomass and lipid productivities were pH 7.5?>?pH 7?>?pH 8?>?pH 6.5 and pH 7?>?pH 7.5?=?pH 8?>?pH 6.5?>?pH 6?>?pH 5.5 for T. suecica CS-187 and Chlorella sp, respectively. The effect of various inorganic carbon on growth and productivities of T. suecica (regulated at pH?=?7.5) and Chlorella sp (regulated at pH?=?7) grown in bag photobioreactors was also examined outdoor at the International Power Hazelwood, Gippsland, Victoria, Australia. The highest biomass and lipid productivities of T. suecica (51.45?±?2.67 mg biomass L^?1 day^?1 and 14.8?±?2.46 mg lipid L^?1 day^?1) and Chlorella sp (60.00?±?2.4 mg biomass L^?1 day^?1 and 13.70?±?1.35 mg lipid L^?1 day^?1) were achieved when grown using CO₂ as inorganic carbon source. No significant differences were found between CO₂ and flue gas biomass and lipid productivities. While grown using CO₂ and flue gas, biomass productivities were 10, 13 and 18 %, and 7, 14 and 19 % higher than NaHCO₃, HCl and unregulated pH for T. suecica and Chlorella sp, respectively. Addition of inorganic carbon increased specific growth rate and lipid content but reduced biomass yield and cell weight of T. suecica. Addition of inorganic carbon increased yield but did not change specific growth rate, cell weight or content of the cell weight of Chlorella sp. Both strains showed significantly higher maximum quantum yield (F_v/F_m) when grown under optimum pH.