Enhanced Oil Biodegradation Using Immobilised Rhodococcus-Dietzia Consortium on Agricultural Waste

Modeling Of Alcohol Fermentation In Brewing – Comparative Assessment Of Flavor Profile Of Beers Produced With Free And Immobilized Cells

Biodegradation of Crude Oil in Contaminated Soils by Free and Immobilized Microorganisms

Atrazine removal in agricultural infiltrate by bioaugmented polyvinyl alcohol immobilized and free Agrobacterium radiobacter J14a: A sand column study

Atrazine remediation in agricultural infiltrate by bioaugmented polyvinyl alcohol immobilized and free Agrobacterium radiobacter J14a

Petroleum contamination of marine environments due to exploitation and accidental spills causes serious harm to ecosystems. Bioremediation with immobilized microorganisms is an environmentally friendly and cost-effective emerging technology for treating oil-polluted environments. In this study, Bacillus licheniformis was entrapped in Ca alginate beads using the electrospray technique for light crude oil biodegradation. Three important process variables, including inoculum size (5-15% v/v), initial oil concentration (1500-3500ppm), and NaCl concentration (0-30g/L), were optimized to obtain the best response of crude oil removal using response surface methodology (RSM) and Box-Behnken design (BBD). The highest crude oil removal of 79.58% was obtained for 1500ppm of crude oil after 14days using immobilized cells, and it was lower for freely suspended cells (64.77%). Our result showed similar trends in the effect of variables on the oil biodegradation rate in both free cell (FC) and immobilized cell (IC) systems. However, according to the analysis of variance (ANOVA) results, the extent of the variables' effectiveness was different in FC and IC systems. In the immobilized cell system, all variables had a greater effect on the rate of light crude oil degradation. Moreover, to evaluate the effectiveness of free and immobilized B. licheniformis in bioremediation of an actual polluted site, the crude oil spill in natural seawater was investigated. The results suggested the stability of beads in the seawater, as well as high degradation of petroleum hydrocarbons by free and immobilized cells in the presence of indigenous microorganisms.

Cadmium biosorption by free and immobilized cells from activated sludge was studied in batch experiments to determine the effects of immobilization on the biosorption properties of the microorganisms. The method of immobilization consisted of the entrapment of the microorganisms in calcium alginate beads. In a first step, the time course of cadmium uptake and the effects of pH and temperature on biosorption were studied in each case. Then the biosorption pattern and the effect of biosorbent concentration were investigated. It was found that the magnitudes of the effects of pH and temperature on biosorption were reduced by the entrapment of the cells, but the major effects of the entrapment consisted of a very high reduction of the biosorption rate and a modification of the biosorption pattern. On the one hand, cadmium biosorption by free cells followed the pattern of the Freundlich isotherm over wide ranges of cell and cadmium concentrations in solution. On the other hand, biosorption by the beads could be described by the Freundlich isotherm only when bead concentration was kept constant because the parameters K and n varied with bead concentration. Finally, it was found that, as expected, the entrapment of the cells significantly reduced their intrinsic biosorption capacity due to a loss of available binding sites. For cases where biosorption is the primary objective, free cell systems should therefore be preferred to entrapped cell processes to remove cadmium from aqueous effluents by using activated sludge. Biosorption isotherms show that cadmium can be biosorbed up to more than 20,000 times above water concentrations utilizing free cells at 30 °C and pH 6.6. However, the numerous advantages of immobilized cells in reactor operation should also be considered to select the appropriate technology.

One of the foremost environmental issues having a key role in the feasibility study of polycyclic aromatic hydrocarbons (PAHs) biodegradation is the concern of the toxicity of the formed intermediate metabolites. In this study, biodegradability of phenanthrene (PHE) at initial concentrations of 100-500ppm and its hydroxylated intermediate metabolites (IMs) in aqueous phase were investigated using free cells (FC) and immobilized cells (IC) in polyvinyl alcohol (PVA) cryogel beads. Results showed that both FC and IC systems were capable of complete PHE biodegradation at initial concentrations lower than 250ppm after 7days, though IC system showed a higher PHE removal rate. The maximum IM concentrations observed at initial PHE concentrations of 100 and 250ppm were 20 and 49ppm for FC system, whereas 7.4 and 19ppm were obtained for IC system, respectively, and IMs were finally removed after 7days. Similarly, at 500ppm, IC system resulted in higher removal of PHE compared to FC system. However, during the 7-day period for FC system, IMs concentration rose up to 59ppm, while for IC system, IMs concentration reaches a maximum at day 5 and thereafter it follows a negative rate. It was also shown that resorcinol as an indicator of hydroxylated aromatic metabolites at concentrations of 0-100ppm can well be biodegraded by free and immobilized cell systems. No prohibition on PHE biodegradation could hence occur due to IMs formation. Additionally, stability of IC system was examined in repeated-batch cultures, showing the effective removal of PHE up to nine reuse cycles.

Fermented rice noodle is a major source of food industry generating highly complex organic content (starch) wastewater. This study investigated the treatment of fermented rice noodle wastewater using calcium alginate entrapped yeast cells compared to the free cells. The treatment includes a two-step process: acid hydrolysis for breaking down starch to glucose and fermentation for degrading glucose to ethanol. Yeast culture, Saccharomyces cerevisiae, was used in this study. The experiment was conducted to examine optimum acid concentration and cell entrapment condition for fermentation. Sulfuric acid concentrations ranged from 0.25 to 1.00% by volume were tested while the cells entrapped in calcium alginate at cell-to-matrix (alginate) ratios (by volume) of 1:5, 1:10, and 1:20 were varied. The result showed that the optimum acid concentration of 1.00% provided 5-time higher glucose concentration compared to that in raw wastewater. After the batch fermentation, the entrapped cells reduced total chemical oxygen demand (COD) by 33-46% and glucose concentration by 88-90% while the free cells cannot obviously remove COD and reduced glucose concentration by 62%. The entrapped cells at the cell-to-matrix ratio of 1:5 achieved the best glucose biotransformation performance. The treatment reaction followed second-order kinetics. The entrapped and free cell systems gave the treatments with kinetic constants of 0.007 to 0.010 and 0.001 L/mg/hr, respectively. The entrapped and free yeast cell system potentially produced ethanol of 643 to 801 mg/L.

Nitrile degradation by Candida guilliermondii CCT 7207 using free and immobilized cell systems was compared. Different specific growth rates were observed for immobilized (mumax=0.021 h(-1)) and the free cells (mumax=0.029 h(-1)). The maximum specific rate of acetic acid formation was 0.387 h(-1) and 0.266 h(-1) for free and immobilized cells, respectively. Cell adhesion to the support materials was confirmed by scanning electron microscopy. When immobilized, the yeast was able to use high nitrile and amide concentrations (aliphatic and aromatic) as nitrogen sources. The results suggest that C. guilliermondii CCT 7207 presents a physiological pattern potentially useful for the bioremediation of polluted environments or for the bioproduction of amides and organic acid of high commercial value.

Fruit wine produced from cagaita (Eugenia dysenterica DC) by both free and immobilised yeast cell fermentation

Comparative study of bioethanol production from bagasse pith by Pichia stipitis in free cell system and immobilized electrosprayed micro-beads: SSF and combined hydrolysates fermentation

Biodegradation of propionitrile by Klebsiella oxytoca immobilized in alginate and cellulose triacetate gel

The inulinase-active whole cells of yeast Kluyveromyces marxianus were immobilized by entrapment into agar gel with 76% retention of the enzymatic activity. The enzymatic properties of the immobilized cells were investigated and compared with those of free cells. The immobilization procedure did not alter the optimum pH of the enzymatic preparation. The optimum pH of both free and immobilized cells was 6. The optimum temperature for inulin hydrolysis with the immobilized cells was 5°C higher than that with the free cells. Activation energies for the reaction with the free and immobilized cells were calculated to be 25.62kJ/mol and 13.27kJ/mol, respectively. Km values were 8.3mM inulin for the free cells and 10.5mM for the immobilized cells. Free and immobilized cells showed fairly stable activities between pH 4 to 7 but free cell inulinase was more labile at other pH values compared to the immobilized counterpart. Thermal stability of the enzyme was improved by immobilization. There was no loss of activity of the immobilized cells on storage at 4°C for 30 days.

Pseudomonas aeruginosa UG2Lr, a rifampicin‐resistant strain possessing the luxAB on a chromosomal Tn5 insert, was inoculated into soil microcosms as either free cells or encapsulated in dry alginate beads. A 100‐fold increase in cell number g‐1 dry soil was observed in microcosms inoculated with alginate‐encapsulated UG2Lr after 3 weeks incubation at 22°C compared to microcosms inoculated with free cells. After 98 d, microcosms inoculated with free UG2Lr cells contained 104 cfu g‐1 dry soil compared to 107 cfu g‐1 dry soil in microcosms inoculated with alginate‐encapsulated UG2Lr cells. The effects of disinfectants on both the free and alginate‐encapsulated UG2Lr cells were also examined. 1·0% (w/g dry soil) calcium hypochlorite, formaldehyde and Spectrum Clear Bath, were added to microcosms each week for 4 weeks. Formaldehyde killed both free and alginate‐encapsulated UG2Lr cells within 14 d after only two amendments. Calcium hypochlorite reduced free UG2Lr cell numbers 10‐fold 2 d after initial application; however, the introduced population recovered and was unaffected by subsequent treatments at 7, 14 and 21 d. Alginate‐encapsulated UG2Lr cells were not affected by calcium hypochlorite treatment. Spectrum Clear Bath did not kill either free or alginate‐encapsulated UG2Lr cells in soil. Alginate encapsulation improved survival of introduced bacteria in soil except in the presence of formaldehyde. Killing genetically‐engineered bacteria in soil may be difficult unless a powerful disinfectant such as formaldehyde is used or the genetically‐engineered micro‐organism is allowed to become non‐viable over time.

Bioaugmentation of carbofuran residues in soil using Burkholderia cepacia PCL3 adsorbed on agricultural residues