Evaluation of the Anti-Cancer Potential of Rosa damascena Mill. Callus Extracts against the Human Colorectal Adenocarcinoma Cell Line.

Chemotherapy is an aggressive form of chemical drug therapy aiming to destroy cancer cells. Adjuvant therapy may reduce hazards of chemotherapy and help in destroying these cells when obtained from natural products, such as medical plants. In this study, the potential therapeutic effect of Rosa damascena callus crude extract produced in vitamin-enhanced media is investigated on colorectal cancer cell line Caco-2. Two elicitors, i.e., L-ascorbic acid and citric acid at a concentration of 0.5 g/L were added to the callus induction medium. Callus extraction and the GC-MS analysis of methanolic crude extracts were also determined. Cytotoxicity, clonogenicity, proliferation and migration of Caco-2 colorectal cancer cells were investigated using MTT cytotoxicity, colony-forming, Ki-67 flow cytometry proliferation and Migration Scratch assays, respectively. Our results indicated that L-ascorbic acid treatment enhanced callus growth parameters and improved secondary metabolite contents. It showed the least IC50 value of 137 ug/mL compared to 237 ug/mL and 180 ug/mL in the citric acid-treated and control group. We can conclude that R. damascena callus elicited by L-ascorbic acid improved growth and secondary metabolite contents as well as having an efficient antiproliferative, anti-clonogenic and anti-migratory effect on Caco-2 cancer cells, thus, can be used as an adjuvant anti-cancer therapy.

Detection of Cr6+ by the sulfur oxidizing bacteria biosensor: effect of different physical factors.

A biosensor based on sulfur-oxidizing bacteria (SOB) for detection of toxic chemicals in water was developed. SOB are acidophilic microorganisms that get their energy through the oxidation of reduced sulfur compounds in the presence of oxygen to produce sulfuric acid. The reaction results in an increase in electrical conductivity (EC) and a decrease in pH. The bioassay is based on the inhibition of SOB in the presence of toxic chemicals by measuring changes in EC and pH. The effect of different physical factors such as HRT, inorganic sulfur (S°) particle size, and temperature on detection of Cr(6+) was studied. The detection of Cr(6+) (50 ppb) was improved by decreasing the hydraulic retention time (HRT) from 30 to 10 min and increasing S° particle size from 1 to 4.75 mm. Detection time was shorter at 30 °C compared to 45 °C and the SOB were active over a wide range of temperatures with a maximum temperature for growth at 45 °C. This novel biosensor is simple, highly sensitive to low Cr(6+) concentrations (50 ppb), and also minimizes detection time. The present findings can be applied to the proper continuous screening of water ecosystem toxicity.

Process optimization of batch biosorption of lead using Lactobacillius bulgaricus in an aqueous phase system using response surface methodology.

Response surface methodology (RSM) based on central composite rotatable design was used to investigate the effects of operating variable, mainly, pH, weight of biomass, and initial lead ion concentration on the lead adsorption capacity at ambient temperature using dried cells of Lactobacillius bulgaricus. Using RSM, quadratic polynomial equation was obtained for predicting the percent of lead ion removal. Analysis of variance showed that the effects of pH and weight of dried biomass were concluded to be the key factors influencing the capacity of lead ion removal. At pH lower than 2 (high acidic condition) and in alkaline condition, there is no significant biosorption. The optimum percent of lead ion removal was found at pH of 6.78, biomass concentration of 6.58 g/l and initial lead concentration 36.22 ppm. In this condition, percent of lead ion removal was 86.21%. This study showed RSM effectiveness for modeling of biosorption process.

Statistical optimization, kinetic, equilibrium isotherm and thermodynamic studies of copper biosorption onto Rosa damascena leaves as a low-cost biosorbent.

In this study, Rosa damascena leaf powder was evaluated as a biosorbent for the removal of copper from aqueous solutions. Process variables such as the biosorbent dose, pH, and initial copper concentration were optimized using response surface methodology. A quadratic model was established to relate the factors to the response based on the Box-Behnken design. Analysis of variance (ANOVA) was used to assess the experimental data, and multiple regression analysis was used to fit it to a second-order polynomial equation. A biosorbent dose of 4.0 g/L, pH of 5.5, and initial copper concentration of 55 mg/L were determined to be the best conditions for copper removal. The removal of Cu2+ ions was 88.7% under these optimal conditions, indicating that the experimental data and model predictions were in good agreement. The biosorption data were well fitted to the pseudo-second-order and Elovich kinetic models. The combination of film and intra-particle diffusion was found to influence Cu2+ biosorption. The Langmuir and Dubinin-Radushkevich isotherm models best fit the experimental data, showing a monolayer isotherm with a qmax value of 25.13 mg/g obtained under optimal conditions. The thermodynamic parameters showed the spontaneity, feasibility and endothermic nature of adsorption. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the biosorbent before and after Cu2+ biosorption, revealing its outstanding structural characteristics and high surface functional group availability. In addition, immobilized R. damascena leaves adsorbed 90.7% of the copper from aqueous solution, which is more than the amount adsorbed by the free biosorbent (85.3%). The main mechanism of interaction between R. damascena biomass and Cu2+ ions is controlled by both ion exchange and hydrogen bond formation. It can be concluded that R. damascena can be employed as a low-cost biosorbent to remove heavy metals from aqueous solutions.

Kinetic, Isotherm and Thermodynamic Aspects of Zn2+ Biosorption by Spirulina platensis: Optimization of Process Variables by Response Surface Methodology.

The aim of this study was to assess the efficiency of Spirulina platensis for removing Zn2+ ions from the aqueous solutions. The optimized conditions of 4.48 g/L algal dose, pH of 6.62 and initial zinc concentration of 29.72 mg/L obtained by response surface methodology were employed for Zn2+ biosorption by S. platensis and up to 97.90% Zn2+ was removed, showing that there is a favorable harmony between the experimental data and model predictions. Different kinetic and equilibrium models were used to characterize the biosorption manner of Spirulina as a biosorbent. The kinetic manner of Zn2+ biosorption was well characterized by the pseudo-second-order, implying that the adsorption process is chemical in nature. The Langmuir and Dubinin-Radushkevich isotherm models were best fit to the equilibrium data. The maximum adsorption capacity of the Langmuir monolayer was 50.7 mg/g. Furthermore, the thermodynamic analysis revealed that Zn2+ biosorption was endothermic, spontaneous and feasible. As a result of biosorption process, FTIR, SEM, and EDX investigations indicated noticeable alterations in the algal biomass's properties. Therefore, the dried Spirulina biomass has been shown to be cost-effective and efficient for removing the heavy metals, particularly zinc ions from wastewater, and the method is practicable, and environmentally acceptable.

Environmentally azithromycin pharmaceutical wastewater management and synergetic biocompatible approaches of loaded azithromycin@hematite nanoparticles.

Pharmaceutical wastewater contamination via azithromycin antibiotic and the continuous emergence of some strains of bacteria, cancer, and the Covid-19 virus. Azithromycin wastewater treatment using the biosynthesized Hematite nanoparticles (α-HNPs) and the biocompatible activities of the resulted nanosystem were reported. Biofabrication of α-HNPs using Echinacea purpurea liquid extract as a previously reported approach was implemented. An evaluation of the adsorption technique via the biofabricated α-HNPs for the removal of the Azr drug contaminant from the pharmaceutical wastewater was conducted. Adsorption isotherm, kinetics, and thermodynamic parameters of the Azr on the α-HNPs surface have been investigated as a batch mode of equilibrium experiments. Antibacterial, anticancer, and antiviral activities were conducted as Azr@α-HNPs. The optimum conditions for the adsorption study were conducted as solution pH = 10, 150 mg dose of α-HNPs, and Azr concentration 400 mg/L at 293 K. The most fitted isothermal model was described according to the Langmuir model at adsorption capacity 114.05 mg/g in a pseudo-second-order kinetic mechanistic at R2 0.9999. Thermodynamic study manifested that the adsorption behavior is a spontaneous endothermic chemisorption process. Subsequently, studying the biocompatible applications of the Azr@α-HNPs. Azr@α-HNPs antibacterial activity revealed a synergistic effect in the case of Gram-positive more than Gram-negative bacteria. IC50 of Azr@α-HNPs cytotoxicity against MCF7, HepG2, and HCT116 cell lines was investigated and it was found to be 78.1, 81.7, and 93.4 µg/mL respectively. As the first investigation of the antiviral use of Azr@α-HNPs against SARS-CoV-2, it was achieved a safety therapeutic index equal to 25.4 revealing a promising antiviral activity. An admirable impact of the use of the biosynthesized α-HNPs and its removal nanosystem product Azr@α-HNPs was manifested and it may be used soon as a platform of the drug delivery nanosystem for the biomedical applications.

Process optimization and modeling of Cd2+ biosorption onto the free and immobilized Turbinaria ornata using Box-Behnken experimental design.

The release of effluents containing cadmium ions into aquatic ecosystems is hazardous to humans and marine organisms. In the current investigation, biosorption of Cd2+ ions from aqueous solutions by freely suspended and immobilized Turbinaria ornata biomasses was studied. Compared to free cells (94.34%), the maximum Cd2+ removal efficiency reached 98.65% for immobilized cells obtained via Box-Behnken design under optimized conditions comprising algal doses of 5.04 g L-1 and 4.96 g L-1, pH values of 5.06 and 6.84, and initial cadmium concentrations of 25.2 mg L-1 and 26.19 mg L-1, respectively. Langmuir, Freundlich, and Temkin isotherm models were suitably applied, providing the best suit of data for free and immobilized cells, but the Dubinin-Radushkevich model only matched the immobilized algal biomass. The maximum biosorption capacity of Cd2+ ions increased with the immobilized cells (29.6 mg g-1) compared to free cells (23.9 mg g-1). The Cd2+ biosorption data obtained for both biomasses followed pseudo-second-order and Elovich kinetic models. In addition, the biosorption process is controlled by film diffusion followed by intra-particle diffusion. Cd2+ biosorption onto the free and immobilized biomasses was spontaneous, feasible, and endothermic in nature, according to the determined thermodynamic parameters. The algal biomass was further examined via SEM/EDX and FTIR before and after Cd2+ biosorption. SEM/EDX analysis revealed Cd2+ ion binding onto the algal surface. Additionally, FTIR analysis confirmed the presence of numerous functional groups (hydroxyl, carboxyl, amine, phosphate, etc.) participating in Cd2+ biosorption. This study verified that immobilized algal biomasses constitute a cost-effective and favorable biosorbent material for heavy metal removal from ecosystems.

Cefotaxime removal enhancement via bio-nanophotocatalyst α-Fe2O3 using photocatalytic degradation technique and its echo-biomedical applications.

The present paper evaluates the photocatalytic degradation (PCD) performance of the biofabricated hematite nanoparticles (α-HNPs) for the degradation approach of the Cefotaxime (Cfm). The optimum pH of the solution to achieve the best PCD was found to be 10.5. The kinetics study for the PCD of the Cfm via α-HNPs has been investigated and the reaction was found to be fellow pseudo-first-order at R2 = 0.992. The mass loading impact of α-HNPs was investigated and estimated for the maximum degradation of Cfm 0.4 mg/mL. UV-Vis confirmed that α-HNPs had a direct transition bandgap at 3.78 eV at a maximum absorption wavelength of 362 nm with suspension stability for 7 days. The probable mechanism of the Cfm PCD via α-HNPs and the degradation pathway was conducted. The validation of the suspension stability of the α-HNPs (-68.6 ± 11.8 mV) was determined using the zeta potential investigation test. XRD investigation was conducted after Cfm PCD showing an average crystallite size of 27.0 nm. XRD, TEM, SEM, EDX, and FT-IR analyses have been conducted for the α-HNPs before and after Cfm PCD confirming the high efficiency for the reusability of the current biocatalyst α-HNPs for further use. TEM results of the particle sizes of α-HNPs were found at 19.2 ± 4.4 and 20.6 ± 7.4 nm respectively before and after Cfm PCD. The efficiency of the Cfm PCD was found to be 99.1% after 6 h. High potent as an antibacterial agent of α-HNPs was investigated either α-HNPs alone or after its PCD activity against Cfm. The antibacterial activity revealed high sensitivity, especially toward Gram-positive species indicating its promising ability against pathogenic issues. Interestingly, Cfm@α-HNPs showed superior anti-proliferative activity as tested by MTT assay and were able to induce apoptosis in MCF7 and HepG2 cell lines using the flow cytometry technique at 20.7% and 17% respectively. Also, The IC50 of hydrogen peroxide scavenging was estimated and it was manifested that 635.8 and 665.6 µg/mL of α-HNPs before and after the PCD process of Cfm respectively.

Detecting oxidized contaminants in water using sulfur-oxidizing bacteria.

For the rapid and reliable detection of oxidized contaminants (i.e., nitrite, nitrate, perchlorate, dichromate) in water, a novel toxicity detection methodology based on sulfur-oxidizing bacteria (SOB) has been developed. The methodology exploits the ability of SOB to oxidize elemental sulfur to sulfuric acid in the presence of oxygen. The reaction results in an increase in electrical conductivity (EC) and a decrease in pH. When oxidized contaminants were added to the system, the effluent EC decreased and the pH increased due to the inhibition of the SOB. We found that the system can detect these contaminants in the 5-50 ppb range (in the case of NO(3)(-), 10 ppm was detected), which is lower than many whole-cell biosensors to date. At low pH, the oxidized contaminants are mostly in their acid or nonpolar, protonated form which act as uncouplers and make the SOB biosensor more sensitive than other whole-cell biosensors which operate at higher pH values where the contaminants exist as dissociated anions. The SOB biosensor can detect toxicity on the order of minutes to hours which can serve as an early warning so as to not pollute the environment and affect public health.

Assessing acute toxicity of effluent from a textile industry and nearby river waters using sulfur-oxidizing bacteria in continuous mode.

Bioassays are becoming an important tool for assessing the toxicity of complex mixtures of substances in aquatic environments in which Daphnia magna is routinely used as a test organism. Bioassays outweigh physicochemical analyses and are valuable in the decision-making process pertaining to the final discharge of effluents from wastewater treatment plants as they measure the total effect of the discharge which is ecologically relevant. In this study, the aquatic toxicity of a textile plant effluent and river water downstream from the plant were evaluated with sulfur-oxidizing bacterial biosensors in continuous mode. Collected samples were analysed for different physicochemical parameters and 1,4-dioxane was detected in the effluent. The effluent contained a relatively high chemical oxygen demand of 60 mg L(-1), which exceeded the limit set by the Korean government for industrial effluent discharges. Results showed that both the effluent and river waters were toxic to sulfur-oxidizing bacteria. These results show the importance of incorporating bioassays to detect toxicity in wastewater effluents for the sustainable management of water resources.

A review of green methods for phyto-fabrication of hematite (α-Fe2O3) nanoparticles and their characterization, properties, and applications.

The aim of the current work is the introduction of a quick and simple literature survey about the bio-fabrication of the Alpha Hematite nanoparticles (α-Fe2O3) using the plant extracts green method. The survey manifested the utilities of the environmentally friendly biosynthesis methods via extracting different plant species, some of its important physicochemical properties, various instrumental analysis characterization tools, and potential applications.

Biosorptive capacity of Cd(II) and Cu(II) by lyophilized cells of Pseudomonas stutzeri.

The biosorptive capacity of Cd(II) and Cu(II) by lyophilized cells of Pseudomonas stutzeri was investigated based on Langmuir and Freundlich isotherms and biosorption kinetics were analyzed using first order kinetic with different initial metal concentrations. Biosorptive capacity for Cd(II) and Cu(II) decreased with an increment of metal concentration, reaching 43.5 and 36.2 mg/g at the initial concentration of 300 mg/L. Biosorption capacity for both metal ions was increased with increasing pH. The optimum pH for biosorption rate of Cu(II) and Cd(II) was pH 5; above pH 5.0 the metal cations came to be precipitated. The experimental data showed a better fit with the Langmuir model over the Freundlich model for both metal ions throughout the range of initial concentrations. The maximum sorptive capacity (q max) obtained from the Langmuir equation for Cd(II) and Cu(II) were 47.86 (r(2)=0.99) and 33.16 (r(2)=0.99), respectively. The bacterial cells have more affinity to adsorb cadmium than copper. The first order kinetic was well fitted to the experimental data for initial concentrations from 30 to 100 mg/L during reaction times of 250 min. These results suggest that biosorption of Cu(II) and Cd(II) by lyophilized cells of P. stutzeri is a potential metal removal strategy.

Rapid detection of heavy metal-induced toxicity in water using a fed-batch sulfur-oxidizing bacteria (SOB) bioreactor.

A fed-batch bioreactor based on sulfur-oxidizing bacteria (SOB) was tested for rapid detection of heavy metal-induced toxicity in water. For this evaluation, SOB were exposed to water contaminated by selenium, mercury, hexavalent chromium, arsenic, cyanide, cadmium, and lead for 2 h and their inhibition rates were analyzed based on changes in electrical conductivity (EC). The results demonstrate that SOB were highly inhibited by selenium, mercury, hexavalent chromium, and arsenic but not by cyanide, cadmium, and lead. The 2 h half maximum effective concentrations (EC50) of SOB for selenium, mercury, hexavalent chromium, and arsenic were estimated to be 0.33, 0.89, 1.18, and 0.24 mg/L, respectively, which are comparable or lower than earlier reports in the literature. However, the EC50 or EC20 values of SOB for cyanide, cadmium, and lead were notably higher compared to findings from previous toxicity tests that employed other microorganisms. The findings from the current study suggest that the fed-batch SOB bioreactor is suitable for rapid detection of toxicity induced by selenium, mercury, hexavalent chromium, and arsenic in water.

Real-time monitoring of water quality of stream water using sulfur-oxidizing bacteria as bio-indicator.

In aquatic ecosystems, real-time water-quality (WQ) biomonitoring has become the most effective technology for monitoring toxic events by using living organisms as a biosensor. In this study, an online WQ monitoring system using sulfur oxidizing bacteria (SOB) was tested to monitor WQ changes in real-time in natural stream water. The WQ monitoring system consisted of three SOB reactors (one continuous and two semi-continuous mode reactors). The SOB system did not detect any toxicity in relatively-unpolluted, natural stream water when operated for more than six months. When diluted swine wastewater (50:1) was added to the influent of the reactors, the system detected toxic conditions in both the continuous and semi-continuous operational modes, showing 90% inhibition of SOB activity within 1 h of operation. The addition of 30 mg/L NO2--N or 2 mg/L of Cr6+ to the influents of SOB reactors resulted in the complete inhibition of the SOB activity within 1-2 h. The results demonstrated the successful application of an SOB bioassay as an online toxicity monitoring system for detecting pollutants from stream or river waters.

Potentiality of Neopestalotiopsis clavispora ASU1 in biosorption of cadmium and zinc.

In this study, a fungal isolate was isolated from avocado fruit collected from a market in Makkah city, Saudi Arabia, and identified as Neopestalotiopsis clavispora ASU1. The biomass of Neopestalotiopsis clavispora ASU1 was used as a natural bio-sorbent for removal of Cd(II) and Zn(II) from aqueous solutions. Characterization of fungal biomass was performed using Fourier transform infrared spectroscopy, X-ray Diffractometer, and BET surface area. Different factors on Cd(II) and Zn(II) biosorption were studied to evaluate the maximum conditions for metals biosorption. The (qmax) for Cd(II) and Zn (II) by N. clavispora ASU1 calculated from the Langmuir adsorption isotherm was 185.3 ±â€¯0.25 and 153.8 ±â€¯0.21 mg/g, respectively. Based on r2, the equilibrium biosorption isotherms fitted well with Langmuir model than Freundlich isotherm. The adsorption kinetics was studied, and the biosorption followed to the pseudo-second-order model. Thus, the current study indicated that the biomass of N. clavispora ASU1 is an effective adsorbent for the removal of heavy metals from aqueous solutions.

Toxicity assessment using different bioassays and microbial biosensors.

Toxicity assessment of water streams, wastewater, and contaminated sediments, is a very important part of environmental pollution monitoring. Evaluation of biological effects using a rapid, sensitive and cost effective method can indicate specific information on ecotoxicity assessment. Recently, different biological assays for toxicity assessment based on higher and lower organisms such as fish, invertebrates, plants and algal cells, and microbial bioassays have been used. This review focuses on microbial biosensors as an analytical device for environmental, food, and biomedical applications. Different techniques which are commonly used in microbial biosensing include amperometry, potentiometry, conductometry, voltammetry, microbial fuel cells, fluorescence, bioluminescence, and colorimetry. Examples of the use of different microbial biosensors in assessing a variety of environments are summarized.

Feasibility of installing and maintaining anaerobiosis using Escherichia coli HD701 as a facultative anaerobe for hydrogen production by Clostridium acetobutylicum ATCC 824 from various carbohydrates.

Using Escherichia coli for installing and maintaining anaerobiosis for hydrogen production by Clostridium acetobutylicum ATCC 824 is a cost-effective approach for industrial hydrogen production, as it does not require reducing agents or sparging with inert gases. This study was devoted for investigating the feasibility for installing and maintaining anaerobiosis of hydrogen production by C. acetobutylicum ATCC 824 when using E. coli HD701 utilizable versus non utilizable sugars as a-carbon source. Using E. coli HD701 for installing anaerobiosis showed a comparable hydrogen production yield and efficiency to the use of reducing agents and nitrogen sparging in case of hydrogen production from the E. coli HD701 non utilizable sugars. In contrast, using E. coli HD701 for installing anaerobiosis showed a lower hydrogen production yield and efficiency than the use of reducing agents and nitrogen sparging in case of using glucose as a substrate. This is possibly because E. coli HD701 when using glucose compensate for the substrate, and produce hydrogen with lower efficiency than C. acetobutylicum ATCC 824. These results indicated that the use of E. coli HD701 for installing anaerobiosis would not be economically feasible when using E. coli HD701 utilizable sugars as a carbon source. In contrast, the use of this approach for installing anaerobiosis for hydrogen production from sucrose and starch would have a high potency for industrial applications.

Synthesis and application of polypyrrole/carrageenan nano-bio composite as a cathode catalyst in microbial fuel cells.

A novel nano-bio composite polypyrrole (PPy)/kappa-carrageenan(KC) was fabricated and characterized for application as a cathode catalyst in a microbial fuel cell (MFC). High resolution SEM and TEM verified the bud-like shape and uniform distribution of the PPy in the KC matrix. X-ray diffraction (XRD) has approved the amorphous structure of the PPy/KC as well. The PPy/KC nano-bio composites were then studied as an electrode material, due to their oxygen reduction reaction (ORR) ability as the cathode catalyst in the MFC and the results were compared with platinum (Pt) as the most common cathode catalyst. The produced power density of the PPy/KC was 72.1 mW/m(2) while it was 46.8 mW/m(2) and 28.8 mW/m(2) for KC and PPy individually. The efficiency of the PPy/KC electrode system is slightly lower than a Pt electrode (79.9 mW/m(2)) but due to the high cost of Pt electrodes, the PPy/KC electrode system has potential to be an alternative electrode system for MFCs.

Effect of organics and alkalinity on the sulfur oxidizing bacteria (SOB) biosensor.

The environmental risk assessment of toxic chemicals in stream water requires the use of a low cost standardized toxicity bioassay. Here, a biosensor for detection of toxic chemicals in stream water was studied using sulfur oxidizing bacteria (SOB) in continuous mode. The biosensor depends on the ability of SOB to oxidize sulfur particles under aerobic conditions to produce sulfuric acid. The reaction results in an increase in electrical conductivity (EC) and a decrease in pH. The biosensor is based on the inhibition of SOB in the presence of toxic chemicals by measuring changes in EC and pH. We found that the SOB biosensor can detect Cr(6+)at a low concentration (50 ppb) which is lower than many whole-cell biosensors. The effect of organic material in real stream water on SOB activity was studied. Due to the presence of mixotrophic SOB, we found that the presence of organic matter increases SOB activity which decreases the biosensor start up period. Low alkalinity (22 mg L(-1) CaCO(3)) increased effluent EC and decreased effluent pH which is optimal for biosensor operation. While at high alkalinity (820 mg L(-1) CaCO(3), the activity of SOB little decreased. We found that system can detect 50 ppb of Cr(6+) at low alkalinity (22 mg L(-1) CaCO(3)) in few hours while, complete inhibition was observed after 35 h of operation at high alkalinity (820 mg L(-1) CaCO(3)).

Power generation from cellulose using mixed and pure cultures of cellulose-degrading bacteria in a microbial fuel cell.

Microbial fuel cells (MFCs) have been used to generate electricity from various organic compounds such as acetate, glucose, and lactate. We demonstrate here that electricity can be produced in an MFC using cellulose as the electron donor source. Tests were conducted using two-chambered MFCs, the anode medium was inoculated with mixed or pure culture of cellulose-degrading bacteria Nocardiopsis sp. KNU (S strain) or Streptomyces enissocaesilis KNU (K strain), and the catholyte in the cathode compartment was 50mM ferricyanide as catholyte. The power density for the mixed culture was 0.188 mW (188 mW/m(2)) at a current of 0.5mA when 1g/L cellulose was used. However, the power density decreased as the cellulose concentration in the anode compartment decreased. The columbic efficiencies (CEs) ranged from 41.5 to 33.4%, corresponding to an initial cellulose concentration of 0.1-1.0 g/L. For the pure culture, cellobioase enzyme was added to increase the conversion of cellulose to simple sugars, since electricity production is very low. The power densities for S and K strain pure cultures with cellobioase were 162 mW/m(2) and 145 mW/m(2), respectively. Cyclic voltammetry (CV) experiments showed the presence of peaks at 380, 500, and 720 mV vs. Ag/AgCl for the mixed bacterial culture, indicating its electrochemical activity without an external mediator. Furthermore, this MFC system employs a unique microbial ecology in which both the electron donor (cellulose) and the electron acceptor (carbon paper) are insoluble.