Third generation biobutanol production by Clostridium beijerinckii in a medium containing mixotrophically cultivated Dunaliella salina biomass.

This study aims the third generation biobutanol production in P2 medium supplemented D. salina biomass mixotrophically cultivated with marble waste (MW). The wastes derived from the marble industry contain approximately 90% of carbon-rich compounds. Microalgal growth in mixotrophic conditions was optimized in the 0.4-2 g/L of MW concentration range. The highest microalgal concentration was obtained as 0.481 g/L in the presence of 1 g/L MW. Furthermore, some important parameters for the production of biobutanol, such as microalgal cultivation conditions, initial mixotrophic microalgal biomass loading (50-300 g/L), and fermentation time (24-96 h) were optimized. The highest biobutanol, total ABE, biobutanol yield and productivity were determined as 11.88 g/L, 13.89 g/L, 0.331 g/g and 0.165 g/L/h at the end of 72 h in P2 medium including 60 g/L glucose and 200 g/L microalgal biomass cultivated in 1 g/L MW, respectively. The results show that D. salina is a suitable raw material for supporting Clostridium beijerinckii DSMZ 6422 cells on biobutanol production. To the best of our knowledge, this is the first study on the use of MW which is a promising feedstock on the mixotrophic cultivation of D. salina for biobutanol production.

Boron bio-mining by high boron-tolerant native microalgae in Turkey and boron toxicity in the aquatic environment.

Boron (B) is one of the most important trace elements. Turkey has the largest B reserves in the world with 3 billion tons of B. Therefore, the toxicity of B is more important in Turkey. In this study, effective B removal was provided by different types of microalgae and then B recovery in culture media by bio-mining was detected. The water of Lake Mogan in Gölbasi/Ankara/Turkey was used as the microalgae culture medium as a cost-reducing factor. The effects of light, temperature, NaNO3 and K2HPO4 stresses on B removal were determined. The highest B removal was 17.19% at 25 µmol/m2s light intensity and 25 °C for Phormidium animale in Lake Mogan culture medium. Boron removal of Scenedesmus sp. was 36.42% at 25 µmol/m2s light intensity, at 25 °C, at 1.5 g/L NaNO3 and 40 mg/L K2HPO4 concentrations in BG11 medium on the 15th day. The chl (a + b) concentration of Scenedesmus sp. was 1.63 µg/mL at 75 µmol/m2s light intensity and the chl (a) concentration of P. animale was 2.01 µg/mL at 25 µmol/m2s light intensity. Considering all parameters, Scenedesmus sp. and P. animale are recommended as effective biomaterials for the B removal process.

Novel application of isolated Micrococcus luteus and Bacillus pumilus for Li+ ion biosorption: a comparative study.

In this study, Li+ biosorption profiles of Micrococcus luteus and Bacillus pumilus bacterial strains were investigated. Comparative surface characterization of the biomasses revealed that B. pumilus had a significantly greater surface negativity than the other, which had a direct positive effect on the ability to attract the Li+ ions. Biosorption experiments showed that B. pumilus cell had more efficient performance at all pH and initial Li+ concentration values in the ranges of 3.0-10.0 and 2.5-20.0 mg/L, respectively. The maximum adsorption capacities obtained at initial Li+ concentration of 20.0 mg/L and pH 9.0 were 1.160 mg Li+/g (167.1 µmol/g) and 2.280 mg Li+/g (328.5 µmol/g) for M. luteus and B. pumilus, respectively. For all the cases studied, the biosorption equilibrium was reached very quickly, suggesting that physical interaction dominated this process. Experimental data were found to be compatible with both Langmuir and Freundlich models under the studied experimental conditions. This study highlights the idea that B. pumilus bacterial strain will be a new and preferred biosorbent for Li+ ions by providing a low cost, rapid and quite efficient process.

Determination of Bioethanol Production from Apricot (Prunus armeniaca) Pomace

Abstract Fruit juice industry generates massive amount of lignocellulosic by-products annually which are excellent raw materials for bioethanol production. In the current study, bioethanol production from apricot (Prunus armeniaca) pomace by Kluyveromyces marxianus was investigated for the first time. Some key parameters for fermentation such as pretreatment methods, biomass and cellulase loading and time, were optimized. Kluyveromyces marxianus produced 30.09 g/L ethanol in the 20% washed apricot pomace and 120 FPU/g cellulose enzyme loading. The highest theoretical yield and Y P/S values were also observed as 94.7% and 0.50 g/g, respectively, when 15 FPU/g cellulose enzyme was used. These results depict that apricot pomace is a promising feedstock for bioethanol production.

A comparative investigation of lithium(I) biosorption properties of Aspergillus versicolor and Kluyveromyces marxianus.

In the current batch study, lithium(I) ion sorption behaviors of Aspergillus versicolor fungus and newly isolated Kluyveromyces marxianus yeast were investigated comparatively. Surface and structural characterization studies of the biosorbents carried out with Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), surface area and zeta potential analyses showed that isolated K. marxianus yeast from salty wastes has more preferable properties (i.e. higher porosity, surface area and negativity) for cation sorption. Biosorption studies also supported this estimation; higher lithium(I) sorption capacities were obtained with K. marxianus cells at all experimental conditions studied. Rapid sorption profiles of the sorbents demonstrated that physical interaction is the main mechanism in this system. The effects of pH and initial lithium(I) concentration on the lithium(I) sorption capacities of biosorbents were examined. The maximum adsorption capacities of 347.9 and 409.2 µmol lithium(I)/g biosorbent were obtained at an initial lithium(I) concentration of 20 mg/L at pH 9.0 using A. versicolor and K. marxianus, respectively. The equilibrium data fitted both Langmuir and Freundlich models in the concentration ranges studied. This study revealed that K. marxianus yeast can be used for effective, rapid and low cost capture process of lithium(I) ions from aqueous solutions.

Improvement of bioethanol production from pomegranate peels via acidic pretreatment and enzymatic hydrolysis.

The aim of this study was to improve the ethanol production from pomegranate peels (PPs). Therefore, the effect of enzymatic hydrolysis and different pretreatments on ethanol production by yeasts was examined. There were three different enzyme concentrations (3.6, 7.2, 14.4 FPU/g substrate) tested for enzymatic hydrolysis, and four different PP media, such as WSPP (whole slurry of PP), LFPP (liquid fraction of PP), WSFPP (washed solid fraction of PP) and N-WSFPP (non-washed solid fraction of PP), were prepared. Bioethanol production was monitored for 96 h. Maximum ethanol concentrations were obtained at WSPP medium as 12.69 g/L, 14.35 g/L and 4.23 g/L in Saccharomyces cerevisiae, Kluyveromyces marxianus and Pichia stipitis, respectively. On the other hand, the washing step of biomass increased the kinetic parameters dramatically and the highest theoretical ethanol yields and YP/S values were obtained from WSFPP medium in all tested yeasts. Theoretical ethanol yields were 97.8%, 98.7% and 35.5% for S. cerevisiae, K. marxianus and P. stipitis, respectively. Qp values were observed as 0.98 g/L h, 0.99 g/L h and 0.04 g/L h for the same yeasts. The highest YP/S values were detected as 0.50 g/g for S. cerevisiae, 0.50 g/g for K. marxianus and 0.30 g/g for P. stipitis in the washed pomegranate peel biomass.

Efficient approaches to convert Coniochaeta hoffmannii lipids into biodiesel by in-situ transesterification.

Coniochaeta hoffmannii was isolated from soils contaminated with biscuit factory wastes showed the maximum lipid accumulation capacity in the study. Lipid production was optimized in terms of pH, carrot pomace loading, nitrogen type and amount, incubation time. Solvent, alcohol type and catalyst concentration, dried/wet biomass concentration, reaction approaches and time were optimized for lipid extraction and transesterification. The highest lipid accumulation was found as 52.0% at pH 4 in the presence of 10% carrot pomace, 0.5 g/L cheese whey at the end of the 48 h incubation. The maximum total C16 and C18 FAME rates were detected at the 25 °C, in the presence of 4 g/L dried C. hoffmannii biomass, methanol and 3% NaOH by using the in-situ transesterification process at the end of the 0.5 h as 96.3%. This is the first report about the usage of C. hoffmannii lipids obtained from carrot pomace for sustainable biodiesel production.

Effective biosorption of phenol by the thermophilic cyanobacterium Phormidium sp.

The use of microbial biomass as biosorbent for phenol removal has been extensively studied, but its removal by biosorption by thermophilic cyanobacterium Phormidium sp. has not been investigated to the best of our knowledge. In the present study, some important parameters for biosorption process were optimized, starting with testing the effects of different pH values ranging from 1 to 12, and then initial phenol concentrations of 45.1, 115.3, 181.4, 243.3, 339.9 mg/L on phenol uptake. The efficiency of removal from aqueous solution was higher within the pH 6-8 range, with the maximum of 100% at pH 7 after 24 hours of adsorption time. The highest specific rate was observed as 165.1 mg/g in the presence of 339.9 mg/l initial phenol concentration. The Freundlich adsorption models were fitted to the equilibrium data, which indicated that phenol ions were favourably adsorbed by Phormidium sp.

Dual bioremediation of phenol and Cr(VI) by mixed microbial cultures in the presence of molasses.

Simultaneous phenol and Cr(VI) bioremoval by two different mixed cultures, from petroleum-contaminated soil (PS) and boron-contaminated wastewater (BW), was investigated in regard to different culture media, pH levels (6-8), initial phenol (25-100 mg/L) and Cr(VI) (15-50 mg/L) concentrations. The optimum medium was found to be mineral salt medium tested, which contained 1% (v/v) molasses (MSM). Optimum pH values were 6 for PS and 8 for BW. All of the phenol present in the samples was mineralized regardless of its concentrations tested, Cr(VI) bioremoval was enhanced by the increase in phenol concentrations, and molasses also exerted a positive effect on Cr(VI) removal, and the yields reached 100% for both pollutants, even at 13.1 mg/L Cr(VI) and 91.1 mg/L phenol concentration in PS samples. In MSM containing PS samples approximate efficiency was 100% for phenol removal; but Cr(VI) removal ratios were 64.9% and 41.7% at 25.8 mg/L and 41.3 mg/L concentrations, respectively. Finally it can be concluded that molasses stimulated Cr(VI) bioremoval at elevated phenolic conditions in the mixed microbial culture, and molasses might be of use for the bioremediation of phenol and Cr(VI) polluted wastewaters.

A new and effective approach to boron removal by using novel boron-specific fungi isolated from boron mining wastewater.

Boron-resistant fungi were isolated from the wastewater of a boron mine in Turkey. Boron removal efficiencies of Penicillium crustosum and Rhodotorula mucilaginosa were detected in different media compositions. Minimal Salt Medium (MSM) and two different waste media containing molasses (WM-1) or whey + molasses (WM-2) were tested to make this process cost effective when scaled up. Both isolates achieved high boron removal yields at the highest boron concentrations tested in MSM and WM-1. The maximum boron removal yield by P. crustosum was 45.68% at 33.95 mg l(-1) initial boron concentration in MSM, and was 38.97% at 42.76 mg l(-1) boron for R. mucilaginosa, which seemed to offer an economically feasible method of removing boron from the effluents.

EPS production and bioremoval of heavy metals by mixed and pure bacterial cultures isolated from Ankara Stream.

This study is focused on isolation of Ni(II), Cu(II) and Cr(VI) resistant bacteria to assess their exopolysaccharide (EPS) production and related bioremoval capacities. Mixed cultures had higher heavy metal removal capacity in media with molasses (MAS) than the control cultures lacking this carbon (AS) containing 50 mg/l of heavy metal. The yields were 32%, 75.7%, and 51.1% in MAS, while the corresponding values were 29%, 55.1%, and 34.5% in AS, respectively. Purification of the strains 1, 5 and 6 present in the mixed cultures decreased the bioremoval capacities of the mixed culture samples, although these strains produced higher EPS amounts in MAS agar. Strain 5 had the highest Cu(II) (69.1%) and Cr(VI) (43.1%) removal rates at 25 mg/l initial concentration of each pollutant with EPS amounts of 0.74 g/l and 1.05 g/l, respectively. This strain was identified as Stenotrophomonas maltophilia. The presented data show that especially mixed and also pure cultures of bacterial strains isolated from Ankara Stream could be assessed as potential bioremoval agents in the treatment of Cu(II) or Cr(VI) containing wastewaters.

Detection of boron removal capacities of different microorganisms in wastewater and effective removal process.

In this study boron removal capacities of different microorganisms were tested. Candida tropicalis, Rhodotorula mucilaginosa, Micrococcus luteus, Bacillus thuringiensis, Bacillus cereus, Bacillus megaterium, Bacillus pumilus, Pseudomonas aeruginosa and Aspergillus versicolor were examined for their boron bioaccumulation capacities in simulated municipal wastewater. A. versicolor and B. cereus were found as the most boron-tolerant microorganisms in the experiments. Also boron bioaccumulation yield of A. versicolor was 49.25% at 15 mg/L boron concentration. On the other hand biosorption experiments revealed that A. versicolor was more capable of boron removal in inactive form at the highest boron concentrations. In this paper maximum boron bioaccumulation yield was detected as 39.08% at 24.17 mg/L and the maximum boron biosorption yield was detected as 41.36% at 24.01 mg/L boron concentrations.

Biodegradation of pesticide triclosan by A. versicolor in simulated wastewater and semi-synthetic media.

Triclosan is known as an antimicrobial agent, a powerful bacteriostat and an important pesticide. In this paper biodegradation of triclosan by Aspergillus versicolor was investigated. Effects of simulated wastewater and semi-synthetic media on fungal triclosan degradation process were detected. HPLC analysis showed that fungal triclosan biodegradation yield was 71.91% at about 7.5 mg/L concentration in semi-synthetic medium and was 37.47% in simulated wastewater. Fungus could be able to tolerate the highest triclosan concentration (15.69 mg/L). The biodegradation yield was 29.81% and qm was 2.22 mg/g at this concentration. Some of the parameters, such as pH, culture media, increasing triclosan and biomass concentrations were optimized in order to achieve the effective triclosan biodegradation process. The highest triclosan biodegradation yields of all microorganisms were achieved by A. versicolor.

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.

Evaluation of biotechnological potentials of some industrial fungi in economical lipid accumulation and biofuel production as a field of use.

Considering the vast number of scientific reports on various potential uses of fungi, there was an attempt to select the best lipid producer of some fungi at optimized conditions (Aspergillus versicolor, Rhizopus oryzae, Rhizopus arrhizus, Tramates versicolor). The aim was to offer new fields of use to the industries already culturing and using such materials. Aspergillus versicolor mycelia were found to be accumulating the highest amount of lipids. Experiments to improve lipid accumulation and transesterification properties were performed in molasses medium; the first steps were testing the effects of different pH values and different nitrogen sources on lipid accumulation. Various concentrations of KNO(3) (0.5, 1.0, 1.5 gL(-1)) and molasses (6%, 8%, 10%) were tried in order to find the optimum carbon and nitrogen requirements. Maximum lipid content was 22.8% in the samples containing 6% molasses solution and 1.0 gL(-1) KNO(3) at pH 4 after 10 days of incubation. The highest fatty acid ethyl ester yield of these samples was 77% (5.0 ethanol:oil, 0.4 sulfuric acid:oil at 30°C for 6 hr). Since the crude lipids were rich in C16 and C18 fatty acids, this was considered as suitable feedstock for biodiesel production.

Phenol biodegradation by different mixed cultures and the optimization of efficiency of the degradation.

In this study, the phenol degradation capacities of four different mixed cultures, namely, Ankara Stream (AS), petroleum-contaminated soil (PS), olive mill wastewater (OMW), and drug mill wastewater (DMW) were investigated with regards to different pH levels, phenol (497.2-1183.0 mg/L) and biomass concentrations (0.5-3.0%(v/v)). The most efficient culture was selected and the optimal conditions required for its highest performance in phenol degradation were studied. We found 100% phenol degradation for DMW at nearly 1000 mg/L initial concentration. The optimum pH was 8 and the mixed culture could tolerate phenol levels up to approximately 1500 mg/L. The selected culture degraded all of the phenol concentrations ranging from 497.2 to 1183.0 mg/L with 100% efficiency after 48 h and 120 h incubation, respectively. Increasing the biomass concentration from 0.5% to 3.0% (v/v) level decreased the incubation time needed for complete degradation. The data indicate that the mixed culture used in this study can be taken as a good candidate for effective treatment of waters contaminated by phenol.

Utilization of LPG and gasoline engine exhaust emissions by microalgae.

The effect of engine exhaust emissions on air pollution is one of the greatest problems that the world is facing today. The study focused on the effects of realistic levels of engine exhaust emissions of liquid petroleum gas (LPG) and gasoline (GSN) on Phormidium sp. and Chlorella sp. Multi parameters including pH, different medial compositions, fuel types, flow rates and biomass concentrations were described in detail. Effects of some growth factors such as triacontanol (TRIA) and salicylic acid (SA) have also been tested. The maximum biomass concentration of Phormidium sp. reached after 15 days at 0.36 and 0.15 g/L initial biomass concentrations were found as 1.160 g/L for LPG emission treated cultures and 1.331 g/L for GSN emission treated cultures, respectively. The corresponding figures were 1.478 g/L for LPG emission treated cultures and 1.636 g/L for GSN emission treated cultures at 0.65 and 0.36 g/L initial Chlorella sp. biomass concentrations. This study highlights the significance of using Phormidium sp. and Chlorella sp. for utilization of LPG and GSN engine exhaust emissions by the help of growth factors.

Bioremoval of textile dyes with different chemical structures by Aspergillus versicolor in molasses medium.

Bioremoval of 17 dyes with different chemical structures by Aspergillus versicolor was detected in this study. Maxilon Red GRL (MR-GRL), Everdirect Fast Black VSF (EFB-VSF) and Brillant Blue R (BB-R) were removed better by fungal mycelia. Optimum pH values were found as 6 for all three dyes. In further experiments in the highest dye concentrations tested in this study, 58.3, 100 and 49% removal yields and 14.8, 12.6, 9.0 q(m) values were found for MR-GRL, EFB-VSF and BB-R, respectively. Chemical oxygen demand (COD) reduction after seven days of incubation period and role of laccase activity of Aspergillus sp. were also investigated. COD reduction and laccase activities were 55.6% and 2.93 U/mL for MR-GRL, 90.7% and 3.0 U/mL for EFB-VSF and 69.0% and 1.79 U/mL for BB-R, respectively. According to these results A. versicolor deserves notable attention for removal of these dyes in wastewater effluents.

Biosorption of chromium(VI), nickel(II) and Remazol blue by Rhodotorula muciloginosa biomass.

The passive removal of commonly used reactive dye and two heavy metals, from aqueous solutions by inexpensive biomaterial, yeast Rhodotorula muciloginosa biomass, termed biosorption, was studied with respect to pH, initial dye concentration and initial metal ion concentration. The biomass exhibited maximum dye and chromium(VI) uptake at pH 5 and pH 6 for nickel(II) in media containing 50 mg/L heavy metal and 50 mg/L remazol blue. It was found that the highest chromium(VI) removal yields measured were 31.3% for 49.0 mg/l initial chromium(VI) concentrations. The nickel(II) removal yield was 32.5% for 22.3 mg/L. Higher R. Blue removal yields were obtained, such as 77.1% for 117.5 mg/L. The maximum dye biosorption yield was investigated in medium with a constant dye (approximately 50 mg/L) and increasing heavy metal concentration. In the medium with 48.8, 103.8 and 151.8 mg/L chromium(VI) and constant dye concentration, the maximum chromium(VI) biosorption was 7.4, 9.3 and 17.1%, whereas the maximum dye biosorption was 61.6, 56.6 and 55.9%. The maximum nickel(II) biosorptions in the medium with dye were 38.1, 22.1 and 8.8% at 23.7, 37.7 and 60.1 mg/L nickel(II) concentrations. In these media, dye biosorptions were 93.9, 86.4 and 93.3%, respectively.

Boron bioremoval by a newly isolated Chlorella sp. and its stimulation by growth stimulators.

It has been well documented that excess concentrations of boron (B) causes toxic effects on many of the environmental systems. Although Chlorella sp. has been studied to remove pollutants from water, its capacity to remove B has not been investigated yet. Boron removal levels of newly isolated Chlorella sp. were investigated in BG 11 media with stimulators as triacontanol (TRIA) and/or sodium bicarbonate (NaHCO(3)) and without them, to test if they could increase the removal efficiency by increasing biomass. The assays were performed to determine the effect of different medial compositions, B concentrations, pH and biomass concentrations onto removal efficiency. Boron removal was investigated at 5-10 mg/L range at pH 8 in different medial compositions and maximum removal yield was found as 32.95% at 5.45 mg/L B in media with TRIA and NaHCO(3). The effect of different pH values on the maximum removal yield was investigated at pH 5-9, and the optimum pH was found again 8. The interactive effect of biomass concentration and B removal yield was also investigated at 0.386-1.061 g wet weight/L biomass. The highest removal yield was found as 38.03% at the highest biomass range. This study highlights the importance of using new isolate Chlorella sp. as a new biomaterial for B removal process of waters containing B.