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In this study, the effects of enzymatic hydrolysis on lipid extraction from microalga (Chlorella vulgaris) were investigated prior to biodiesel production. The initial fatty acids content of C. vulgaris was 87.6 mg/g cell. The microalgal cell walls were hydrolyzed by cellulases and then their lipid fractions were extracted using various organic solvents such as hexane, methanol, and chloroform. Optimal pH and temperature for the enzymatic hydrolysis were pH 4.8 and 50 °C, respectively, and the maximal hydrolysis yield was 85.3%, which was achieved after 72 h. After the enzymatic hydrolysis, the lipid extraction yield by the organic solvents was improved compared to when there was no enzymatic hydrolysis process, by 1.29–1.73-fold depending on the solvents used. The total fatty acid methyl ester (FAME) productivity through the enzymatic hydrolysis was higher than when there was no enzymatic hydrolysis, by 1.10–1.69-fold depending on the solvents used. When lipid was extracted from the C. vulgaris after the enzymatic hydrolysis in chloroform-methanol solution, FAME productivity was 59.4 mg FAME/g cell.

Microalgae biorefinement has attracted in intensive academic and industrial interest worldwide for its potential to replace petrol biofuels as economically and environmentally advantageous alternatives. However, harvesting and lipid extraction remain as critical and difficult issues to be resolved. In the present study, four amino-groups functionalized organic-nano clays were prepared. Specifically, Mg or Al or Ca backboned and covalently linked with 3-aminopropyltriethoxysilane or 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane by sol-gel reaction under ambient conditions, resulted in Mg-APTES clay, Al-APTES clay, Ca-APTES clay, and Mg-N3 clay, respectively. Each organic-nanoclay was utilized for lipid extraction from wet microalgae biomass. As a result, the lipid-extraction efficiency of paste docosahexaenoic acid (DHA)-rich Chlorella sp. with low lipid content was high, while one of paste oleaginous Chlorella sp. with high lipid content was relatively low. Despite the low lipid-extraction efficiencies in all of the wet microalgae biomass, the conversion of the extracted lipids' fatty acids to biodiesel was nearly 100%.

Two freshwater microalgae including Chlamydomonas mexicana and Scenedesmus obliquus were grown on Bold Basal Medium (BBM) with different levels of salinity up to 100 mM NaCl. The dry biomass and lipid content of microalgae were improved as the concentration of NaCl increased from 0 to 25 mM. Highest dry weight (0.8 and 0.65 g/L) and lipid content (37 and 34 %) of C. mexicana and S. obliquus, respectively, were obtained in BBM amended with 25 mM NaCl. The fatty acid composition of the investigated species was also improved by the increased NaCl concentration. At 50 mM, NaCl palmitic acid (35 %) and linoleic acid (41 %) were the dominant fatty acids in C. mexicana, while oleic acid (41 %) and α-linolenic acid (20 %) were the major fractions found in S. obliquus.

Effective enhancement of neutral lipid (especially triacylglycerol, TAG) content in microalgae is an important issue for commercialization of microalgal biorefineries. Pressure is a key physical factor affecting the morphological, physiological, and biochemical behaviors of organisms. In this paper, we report a new stress-based method for induction of TAG accumulation in microalgae (specifically, Chlorella sp. KR-1 and Ch. sp. AG20150) by very-short-duration application of mild pressure. Pressure treatments of 10-15bar for 2h resulted in a considerable, ∼55% improvement of the 10-100g/Lcells' TAG contents compared with the untreated control. The post-pressure-treatment increase of cytoplasmic TAG granules was further confirmed by transmission electron microscopy (TEM). Notwithstanding the increased TAG content, the total lipid content was not changed by pressurization, implying that pressure stress possibly induces rapid remodeling/transformation of algal lipids rather than de novo biosynthesis of TAG.

We report an effect involving hydrogen (H2)-plasma-treated nanoporous TiO2(H-TiO2) photocatalysts that improve photocatalytic performance under solar-light illumination. H-TiO2 photocatalysts were prepared by application of hydrogen plasma of assynthesized TiO2(a-TiO2) without annealing process. Compared with the a-TiO2, the H-TiO2 exhibited high anatase/brookite bicrystallinity and a porous structure. Our study demonstrated that H2 plasma is a simple strategy to fabricate H-TiO2 covering a large surface area that offers many active sites for the extension of the adsorption spectra from ultraviolet (UV) to visible range. Notably, the H-TiO2 showed strong ·OH free-radical generation on the TiO2 surface under both UV- and visible-light irradiation with a large responsive surface area, which enhanced photocatalytic efficiency. Under solar-light irradiation, the optimized H-TiO2 120(H2-plasma treatment time: 120 min) photocatalysts showed unprecedentedly excellent removal capability for phenol (Ph), reactive black 5(RB 5), rhodamine B (Rho B) and methylene blue (MB) — approximately four-times higher than those of the other photocatalysts (a-TiO2 and P25) — resulting in complete purification of the water. Such well-purified water (>90%) can utilize culturing of cervical cancer cells (HeLa), breast cancer cells (MCF-7), and keratinocyte cells (HaCaT) while showing minimal cytotoxicity. Significantly, H-TiO2 photocatalysts can be mass-produced and easily processed at room temperature. We believe this novel method can find important environmental and biomedical applications.

Improving lipid productivity and preventing overgrowth of contaminating bacteria are critical issues relevant to the commercialization of the mixotrophic microalgae cultivation process. In this paper, we report the use of magnesium aminoclay (MgAC) nanoparticles for enhanced lipid production from oleaginous Chlorella sp. KR-1 with simultaneous control of KR-1-associated bacterial growth in mixotrophic cultures with glucose as the model substrate. Addition of 0.01–0.1 g/L MgAC promoted microalgal biomass production better than the MgAC-less control, via differential biocidal effects on microalgal and bacterial cells (the latter being more sensitive to MgAC’s bio-toxicity than the former). The inhibition effect of MgAC on co-existing bacteria was, as based on density-gradient-gel-electrophoresis (DGGE) analysis, largely dosage-dependent and species-specific. MgAC also, by inducing an oxidative stress environment, increased both the cell size and lipid content of KR-1, resulting in a considerable, ∼25% improvement of mixotrophic algal lipid productivity (to ∼410 mg FAME/L/d) compared with the untreated control.

Biodiesel production from microalgae depends on the algal biomass and lipid content. Both biomass production and lipid accumulation are limited by several factors in which nutrients play a key role. We investigated the influences of micronutrients on biomass, and lipid content of Micractinium pusillum GU732425 cultivated in bold basal media (BBM). The average dry biomass of microalgal strain in control medium reached 0.34 ± 0.01 g /L, while doubling (2X) the levels of Mn and Cu concentration increased the dry biomass to 0.38 ± 0.01 and 0.37 ± 0.02 g /L, respectively. M. pusillum cultivated in control medium had a biomass of 0.82 ± 0.05 g/L and a lipid productivity of 0.33 ± 0.02 g/L after 17 day cultivation. The alga cultivated in BBM with 4X Mn or 4X Cu produced more biomass (1.25 ± 0.01 or 1.28 ± 0.04 g dw/L) and lipid productivity (0.45±0.04 or 0.47±0.05 g/L), respectively. M. pusillum cultivated in different growth media had fatty acid compositions mainly comprising linoleic (49-54%), palmitic (24-29%), linolenic (16-22%), and oleic acids (2-5%). These results can be used to maximize the production of microalgal biomass and lipids in optimally designed photobioreactors. Key words: Micractinium pusillum, biomass, lipid production, media composition, fatty acids, trace metals

Deoxygenation of microalgal oil obtained by pyrolysis of microalgae was carried out for the production of hydrocarbon fuel from biomass by metal supported catalyst. Oleic acid was used as a model reactant to select an optimized catalyst. Effects of support, metal species, and metal loading on catalytic performance were investigated. Activated carbon showed better performance than silica as a support. Considering various factors in model reaction, such as metal loading, reaction temperature, activity for deoxygenation, and selectivity for decarboxylation, 5 wt% platinum supported on activated carbon (5 wt% Pt/C) was selected as an optimized catalyst. Based on these results, deoxygenation of the pyrolysis oil from Chlorella sp. KR-1 was conducted at 623 and 673 K over this selected catalyst. The product after catalytic deoxygenation was mainly composed of pure hydrocarbons, and its oxygen content was below 2.0%. The fraction in the product of which the boiling point was less than 623 K was about 90%. These properties could allow this upgraded oil to be used for transportation fuel. However, the degree of oxygen removal with microalgal pyrolysis oil was lower than that with oleic acid, implying that impurities in the pyrolysis oil may inhibit the deoxygenation reaction.

The formate-hydrogen lyase (FHL) complex of Escherichia coli catalyzes the conversion of formate to hydrogen (H2) and carbon dioxide (CO2) under anaerobic conditions in the absence of exogenous electron acceptors. The FHL complex consists of formate dehydrogenase (FdhH) and hydrogenase 3 (Hyd3) that are involved in a series of reactions, including formate oxidation (by FdhH), electron transport (by putative five small subunits of Hyd3) and proton reduction (by HycE, large subunit of Hyd3). In this study, the FHL gene cluster and iscR, a negative regulator of iron–sulfur cluster, of E. coli SH5 (BW25113 ΔhycA ΔhyaAB ΔhybBC ΔldhA ΔfrdAB) were altered to increase the FHL-dependent H2 production activity. When FhlA, a transcriptional regulator of FHL, was overexpressed, the FHL-dependent H2 production activity was improved significantly to 2.03 μmol H2 mg−1 cdw min−1 from 1.41 μmol H2 mg−1 cdw min−1. When an iscR deletion and/or fdhF overexpression was added, the whole-cell FHL activity was improved further to 2.80 μmol H2 mg−1 cdw min−1 (with ΔiscR) and 2.45 μmol H2 mg−1 cdw min−1 (with ΔiscR plus fdhF overexpression), respectively. The increase in whole-cell FHL activity was accompanied by an increase in the activity of its member enzymes, such as HycE and/or FdhH. In addition, the highly active recombinant strains exhibited stable performance during prolonged H2 production with the repeated addition of formate. Overall, the FHL-dependent H2 production activity of E. coli can be improved more than three-fold by modifying the expression of the relevant genes.

In the present work, H 2 production from microalgal biomass via dark fermentation was optimized by response surface methodology (RSM). Substrate concentration and initial pH were varied from 3 to 117 g dry cell weight (dcw)/L and 4.2–9.8, respectively. During the fermentation, pH was not controlled. The optimal condition was found at 76 g dcw/L and initial pH of 7.4, under which yielded 31.2 mL H 2 /g dcw. The results of ANOVA verify that the relationship between substrate concentration and initial pH was slightly interdependent or significantly interactive. Besides, the monitoring alkalinity and pH during the confirmation test clearly showed that dark fermentative H 2 production (DFHP) from microalgal biomass was feasible without addition of external alkaline owing to the disruption of cell wall, which provided buffer capacity (max. 3800 mg as CaCO 3 /L). Therefore, although it involved a batch test, this approach would promote the practical viability of DFHP from microalgal biomass. The main organic acids were acetic and butyric acids which are general metabolites found in successful DFHP.

A novel marine hyperthermophile, Thermococcus onnurineus NA1, was found to grow on C1 carbon compounds, such as formate and carbon monoxide (CO), and produce hydrogen (H 2 ). In the present study, the growth and H 2 production of NA1 were examined to determine its potential as H 2 producer. NA1 showed relatively high specific growth rates, 0.48 h −1 and 0.40 h −1 with CO (20%, v/v) and formate (100 mM), respectively, when cultivated in batch mode in a minimal salt medium fortified with 1.0 g L −1 yeast extract. On the other hand, cell growth in both cases stopped at approximately 6 h and the final cell densities were extremely low at 18.2 and 12.1 mg protein L −1 with CO and formate, respectively. The maximum final cell density could be improved greatly to 36.0 mg protein L −1 by optimizing CO content (50%, v/v) and yeast extract concentration (4.0 g L −1 ), but it was still very low. During the cell growth, formate and CO were used as energy source rather than carbon source. In the resting cell experiments, NA1 exhibited remarkably high H 2 production activities as 385.0 and 207.5 μmol mg protein −1 h −1 for CO and formate, respectively. When formate (100 mM) or CO (100%, v/v) was added repeatedly at 30–35 h intervals, NA1 showed consistent H 2 production for 3 cycles with a yield of approximately 1.0 mol H 2 mol −1 for both CO and formate. This study suggests that T. onnurineus NA1 has a high H 2 production potential from formate or CO but a method for achieving a high cell density culture is needed.

Lipids in microalgal biomass were recovered by using pyrolysis method. The pyrolysis experiments of two Chlorella sp. KR-1 samples, which have triglyceride contents of 10.8% and 36.5%, respectively were carried out at to investigate the effects of lipid contents in the cells on the reaction characteristics. The conversion and liquid yield of the lipid-rich sample were higher than those of the lipid-lean sample since its carbon to hydrogen ratio was low. There were low molecular weight organic acids, ketones, aldehydes and alcohols in the liquid products from both KR-1 samples, but the pyrolysis oil of the lipid-rich sample was abundant in free fatty acids, particularly palmitic acid, oleic acid and stearic acid while the content of nitrogen containing organic compounds was low. The microalgal pyrolysis oil had two layers composed of the light hydrophobic fraction and the heavy hydrophilic fraction. The light fraction might be originated from triglycerides and the heavy fraction might be from carbohydrates and proteins. In the light fraction of the liquid products, there were considerable linear alkanes such as pentadecane and heptadecane as well as free fatty acids, implying that deoxygenation reaction including decarboxylation was occurred during the pyrolysis. The yield of the liquid products from the pyrolysis of the KR-1 sample having triglyceride content of 36.5% was 56.9% and the light fraction in the liquid products was 68.2%. Also more than 80% of the light fraction was free fatty acids and pure hydrocarbons, thus showing that most triglycerides could be extracted in the form of suitable raw materials for biofuels.

A catalytic decarboxylation process following pyrolysis was developed for the production of transportation fuels from microalgae. The pyrolysis of Chlorella sp. KR-1, which has a triglyceride content of 36.5%, was carried out at 600 °C to obtain feedstock oil for decarboxylation. The major compounds in the pyrolysis oil were free fatty acids with carbon numbers of 16 and 18. Decarboxylation of the pyrolysis oil was performed using a type of hydrotalcite (MG63) as a catalyst at temperatures of 350 °C and 400 °C. Due to the selective reaction by MG63, hydrocarbons with carbon numbers of 15 and 17 were the most abundant compounds in the liquid product. The product yield at a reaction temperature of 400 °C was 78.6% and the degree of oxygen removal was 78.0%. Inert or less active oxygenates for hydrotalcite, such as phenolic compounds and fatty acid alkyl ester, may prevent the complete removal of oxygen. The diesel fraction in the product obtained under the given reaction condition was 83.8%, whereas that of the pyrolysis oil was 35.5%.

The quantitative relationship between sulfate reducing bacteria (SRB) and hydrogen (H2) production from sulfate (SO42−) and ferrous [Fe(II)] enriched wastewater was investigated. Both Fe(II) (0–11,600 mg/L) and SO42− (0–20,000 mg/L) improved the H2 production efficiency from wastewater. The H2 yields were increased up to 1.9 mol H2/mol glucose in 580–1750 mg Fe(II)/L and 1000–3000 mg SO42−/L enriched wastewater at pH 5.8–6.2. Quantitative Fluorescence In Situ Hybridization (FISH) analyses revealed that the specific sulfate reducing activities (SSRA) were increased from 0.08 and 0.06 to 0.16 and 0.21 g TS/g SRB h in response to variations in sulfate concentration from 300–20,000 mg/L at pH 5.8 and 6.2, respectively. H2 production was not influenced by low SSRA (≤0.1 g TS/g SRB h), which was independent of pH variation. The results demonstrated that the SSRA and Fe(II) concentration can significantly influence on the biological H2 production from SO42− and Fe(II) containing wastewater.

This study assessed the usability of effluent water discharged from a secondary municipal wastewater treatment plant for mass cultivation of microalgae for biofuel production. It was observed that bacteria and protozoa in the effluent water exerted a negative impact on the growth of Chlorella sp. 227. To reduce the effect, filtration or UV-radiation were applied on the effluent water as pre-treatment methods. Of all the pretreatment options tested, the filtration (by 0.2 μm) resulted in the highest biomass and lipid productivity. To be comparable with the growth in the autoclaved effluent water, the filtration with a proper pore size filter (less than 0.45 μm) or UV-B radiation of a proper dose (over 1620 mJ cm−2) are proposed. These findings led us to conclude that the utilization can be realized only when bacteria and other microorganisms are greatly reduced or eliminated from the effluent prior to its use.

The improvement of H2 production capabilities of hydrogen (H2)-producing microorganisms is a challenging issue. Microorganisms have evolved for fast growth and substrate utilization rather than H2 production. To develop good H2-producing biocatalysts, many studies have focused on the redirection and/or reconstruction of cellular metabolisms. These studies included the elimination of enzymes and carbon pathways interfering or competing with H2 production, the incorporation of non-native metabolic pathways leading to H2 production, the utilization of various carbon substrates, the rectification of H2-producting enzymes (nitrogenase and hydrogenase) and photophosphorylation systems, and in silico pathway flux analysis, among others. Owing to these studies, significant improvements in the yield and rate of H2 production, and in the stability of H2 production activity, were reached. This review presents and discusses the recent developments in biohydrogen production, with a focus on metabolic pathway engineering.

Microalgal lipids are the oils of the future for sustainable biodiesel production. One of the most important decisions in obtaining oil from microalgae is the choice of species. A total of 45 algal cultures were isolated from a freshwater lake at Wonju, South Korea. Five microalgal isolates were selected based on their morphology and ease of cultivation under our test conditions. These cultures were identified as strains of Scenedesmus obliquus YSL02, Chlamydomonas pitschmannii YSL03, Chlorella vulgaris YSL04, S. obliquus YSL05, and Chlamydomonas mexicana YSL07 based on microscopic examination and LSU rDNA (D1-D2) sequence analysis. S. obliquus YSL02 reached a higher biomass concentration (1.84 ± 0.30 g L−1) with a lower lipid content (29% w/w), than did Chla. pitschmannii YSL03 (maximum biomass concentration of 1.04 ± 0.09 with a 51% lipid content). Our results suggest that Chla. pitschmannii YSL03 is appropriate for producing biodiesel based on its high lipid content and oleic acid proportion.

Biohydrogen is an ideal energy carrier for mobile chemical fuel cells, but its use is often limited by unavailability of sustained H2 production system(s). Here, we developed a compact system for H2 production from formate based on immobilized cells of recombinant Escherichia coli SH5. Three different matrices were tested as immobilization medium, among which agar showed the best performance in mechanical stability and permeability of substrate(s) and/or gaseous products (H2 and CO2). To explore and optimize the H2 production capability of the immobilized cells, the conditions for cell immobilization including cell loading and agar concentration as well as the factors affecting H2 production rate such as temperature, pH, and substrate concentration were studied in detail. A maximum volumetric production rate of 2.4 L H2 L−1 h−1 was obtained when the immobilized cells were incubated with 350 mM sodium formate at pH 6.5 and 37 °C. Periodic supplementation of 200 mM formate with 20 mM glucose at pH 6.5 maintained the high H2 production rate for a prolonged period of 10 h. We believe that our process can be developed for sustained H2 production and is applicable to the operation of fuel cells in small-scale.

A simple and reliable method based on thermogravimetric analysis has been developed for determining triacylglycerol content in Chlorella sp. KR-1. There are two decomposing steps during pyrolysis of the microalgal cells and the second step of weight loss may be attributed to degradation and volatilization of triacylglycerols. The second peak height in the temperature derivatives of weight loss increased with the triacylglycerol content of the microalgal cells and the peak was around 390 °C regardless of the triacylglycerol contents. Based on these findings, a linear equation for determining triacylglycerol content was derived. The proposed method gives satisfactory results, showing small variance and a good interpolation capability.

Prospecting for robust and high-productivity strains is a strategically important step in the microalgal biodiesel process. In this study, 30 local strains of Chlorella were evaluated in photobioreactors for biodiesel production using coal-fired flue-gas. Three strains (M082, M134, and KR-1) were sequentially selected based on cell growth, lipid content, and fatty acid composition under autotrophic and mixotrophic conditions. Under autotrophic conditions, M082 and M134 showed comparable lipid contents (ca. 230 mg FAME [fatty acid methyl esters derived from microalgal lipids]/g cell) and productivities (ca. 40 mg FAME/L·d) versus a reference strain (KR-1) outdoors with actual flue-gas (CO2, 13%). Interestingly, under mixotrophic conditions, M082 demonstrated, along with maximal lipid content (397 mg FAME/g cell), good tolerance to high temperature (40 °C). Furthermore, the fatty acid methyl esters met important international standards under all of the tested culture conditions. Thus, it was concluded that M082 can be a feedstock of choice for coal-fired, flue-gas-mediated biodiesel production.

Escherichia coli can produce H2 from glucose via formate hydrogen lyase (FHL). In order to improve the H2 production rate and yield, metabolically engineered E. coli strains, which included pathway alterations in their H2 production and central carbon metabolism, were developed and characterized by batch experiments and metabolic flux analysis. Deletion of hycA, a negative regulator for FHL, resulted in twofold increase of FHL activity. Deletion of two uptake hydrogenases (1 (hya) and hydrogenase 2 (hyb)) increased H2 production yield from 1.20 mol/mol glucose to 1.48 mol/mol glucose. Deletion of lactate dehydrogenase (ldhA) and fumarate reductase (frdAB) further improved the H2 yield; 1.80 mol/mol glucose under high H2 pressure or 2.11 mol/mol glucose under reduced H2 pressure. Several batch experiments at varying concentrations of glucose (2.5–10 g/L) and yeast extract (0.3 or 3.0 g/L) were conducted for the strain containing all these genetic alternations, and their carbon and energy balances were analyzed. The metabolic flux analysis revealed that deletion of ldhA and frdAB directed most of the carbons from glucose to the glycolytic pathway leading to H2 production by FHL, not to the pentose phosphate pathway.

The effect of FeSO 4 on continuous H 2 production in a membrane bioreactor (MBR) was investigated using anaerobic mixed microflora under mesophilic condition. The H 2 production of 41.6 l/day was obtained at 10.9 mg FeSO 4 /l, which was 1.59 times higher than that at 2.7 mg FeSO 4 /l. Between 2.7 and 13.7 mg FeSO 4 /l, the H 2 production rate increased in parallel with the H 2 yield under high-cell-density condition. For the same amounts of FeSO 4 , increases in butyric acid together with decreases in lactic acid promoted a reduction of the number of protons and the resultant release of H 2 . The hydrogenase activity of 1.08 mg methylene blue (M.B) reduced/min at 10.9 mg FeSO 4 /l was about sixfold higher than at 2.7 mg FeSO 4 /l. These results suggest that the addition of iron and sulfur to an MBR is an important key factor in the enhancement of H 2 production.

Bioelectrocatalytic hydrogen (H2) production was studied using Thiocapsa roseopersicina hydrogenase in a two-compartment proton-exchange-membrane (PEM) fuel-cell system equipped with carbon–paper electrodes. Sodium dithionite (SD), as an electron donor, and hydrogenase, as a catalyst, were used in the anodic oxidation reaction and in the cathodic reduction reaction, respectively. Methyl viologen (MV) was added for the electron relays in both reactions. The concentrations of phosphate buffer, MV and hydrogenase in the reaction chambers were optimized, in which the concentration of SD was fixed at 20 mM. Parameters including the cathode surface area, the distance between electrodes, and the external load were optimized to complete the system. Catalytic current generation in the cathode increased from 0.12 to 0.19 mA and from 0.07 to 0.12 mA, in proportion to the hydrogenase concentration (34.8–347.5 μg/mL) and the cathode surface area (2.0–11.5 cm2), respectively; however, it decreased from 0.37 to 0.08 mA and from 0.12 to 0.09 mA with the increase of the electrical load (5–1000 Ω) and the distance between electrodes (1.5–3.5 cm), respectively. The optimal MV concentrations were 2.5–5 mM in the cathode chamber. The bioelectrocatalytic H2 production rate was calculated from the cathodic current in argon atmosphere, and the maximal value under the partially optimized conditions was estimated to be 0.16 μmol H2/min/mg-protein, which was less than 8% of the specific H2 production activity, 2.20 μmol H2/min/mg-protein, of the hydrogenase purified from the cytoplasmic fraction of T. roseopersicina. This study indicates that T. roseopersicina hydrogenase has a high potential for bioelectrocatalytic H2 production; still, much effort could be required to develop a proper biofuel-cell system that provides for efficient transfer of electrons and protons.

The application of thermophilic bacteria to the production of hydrogen (H 2 ) from a cellulosic biomass has captured attention of engineering researchers. Thermotoga neapolitana is considered as a potential hydrogen producer because of its ability to be used for the direct H 2 fermentation from raw cellulose, but its H 2 yield is not high. In this study, three chemical pretreatment methods with an ionic liquid, acid and alkali, respectively, were tested on cellulose to enhance the cellulose conversion of this strain into H 2 . Batch cultivations were carried out to investigate the influence of the chemical pretreatment methods on H 2 production under non-sterile conditions. The highest H 2 concentration in the headspace obtained from the ionic liquid-pretreated cellulose was 36.1% (v/v) with ethanol as an anti-solvent. This was clearly higher than that from the acid- and alkali-pretreated celluloses (22–24%). Cultivation with cellulose pretreated with the ionic liquid at a concentration of 10% combining with N 2 sparging showed the maximum cumulative H 2 yield of 1280 mL H 2 /L culture. This value is approximately 10-fold higher than that of raw cellulose (122 mL H 2 /L culture). The H 2 yield obtained from fermentation with ionic liquid-pretreated cellulose was 2.2 mol H 2 /mol glucose equivalents. The results showed that the pretreatment of cellulose using an ionic liquid has considerable potential for improving the direct conversion of cellulosic substrates into H 2 by bacteria.

Hydrogenase from a purple sulfur bacterium, Thiocapsa roseopersicina NCIB 8347, was purified, characterized and investigated for in vitro hydrogen (H 2 ) production. The cell concentration and the specific hydrogenase activity were increased when T. roseopersicina NCIB 8347 was photo-autotropically cultivated with the addition of nutrients every 24h. Crude extracts of the cells were prepared by sonication and then subjected sequentially to ultra-centrifugation, ammonium sulfate fractionation and heat-treatment to remove the impurities. Four-step separation of chromatographic procedures utilizing Q-Sepharose, Phenyl Superose, Mono-Q and Superdex resulted in a 9.56-fold purification with a 0.25% yield of crude cell extract. The optimum pH and temperature for the H 2 evolution of the purified enzyme was 7.0 and 70 °C, respectively, and those for optimum cell growth were 7.0 and 25°C, respectively. The maximum H 2 -evolution activity was exhibited at 70 °C, and when the reaction temperature was decreased to 50°C, the manifest activity fell to 44%. Hydrogenase activities were initially increased in the course of the 50-70 °C heat-treatment, whereas the remaining activities after 5-h heat-treatment at 50 and 70 °C were 110% and 60% of the initial ones, respectively. The purified hydrogenase, at 50 °C and pH 7.0, evolved H 2 gas for approximately 10 days under in vitro conditions, using sodium dithionite and methyl viologen as the electron donor and carrier, respectively.

For the newly isolated chemoheterotrophic bacterium Citrobacter amalonaticus Y19, anaerobic glucose metabolism and hydrogen ( H 2 ) production pathway were studied using batch cultivation and an in silico metabolic-flux analysis. Batch cultivation was conducted under varying initial glucose concentration between 1.5 and 9.5 g/L with quantitative measurement of major metabolites to obtain accurate carbon material balance. The metabolic flux of Y19 was analyzed using a metabolic-pathway model which was constructed from 81 biochemical reactions. The linear optimization program MetaFluxNet was employed for the analysis. When the specific growth rate of cells was chosen as an objective function, the model described the batch culture characteristics of Ci. amalonaticus Y19 reasonably well. When the specific H 2 production rate was selected as an objective function, on the other hand, the achievable maximal H 2 production yield ( 8.7 mol H 2 / mol glucose) and the metabolic pathway enabling the high H 2 yield were identified. The pathway involved non-native NAD(P)-linked hydrogenase and H 2 production from NAD(P)H which were supplied at a high rate from glucose degradation through the pentose phosphate pathway.

The batch fermentations of two hyperthermophilic eubacteria Thermotoga maritima strain DSM 3109 and Thermotoga neapolitana strain DSM 4359 were carried out to optimize the hydrogen production. The simple and economical culture medium using cheap salts with strong buffering capacity was designed based on T. maritima basal medium (TMB). Both strains cultivated under strictly anaerobic conditions showed the best growth at temperature of 75–80 °C and pH of 6.5–7.0. The maximum cell growth of 3.14 g DCW/L and hydrogen production of 342 mL H2 gas/L were obtained, respectively, in the modified TB medium containing 7.5 g/L of glucose and 4 g/L of yeast extract. Hydrogen accumulation in the headspace was more than 30% of the gaseous phase. Cells were also cultivated in cellulose-containing medium to test the feasibility of hydrogen production.

An isolate Citrobacter amalonaticus Y19 showed a typical mixed-acid fermentation with lactate and acetate as major end products when grown anaerobically on glucose and pyruvate, respectively. Production of hydrogen ( H 2 ) from glucose, formate, and reduced methylviologen (MV) and benzylviologen (BV) by the resting cells of Y19 indicates the presence of formate hydrogen lyase (FHL) activity and other hydrogenases. Study with subcellular fractions of Y19 exhibited that the FHL activity, dependent on soluble formate dehydrogenase activity, was detected in the broken cell extract, but not in the soluble or particulate fraction which are separated by centrifugation at 35 , 000 × g . Hydrogen production in the presence of reduced MV or BV was observed in both the soluble and particulate fractions. Uptake hydrogenase activity was observed in both the fractions when the oxidized forms of MV and BV were supplied as electron acceptor. In the soluble fraction, when formate was coupled with oxidized form of MV or BV, hydrogen production activity was recovered. These results indicate that, similar to E. coli, the strain Y19 expresses two different hydrogenases, one as the FHL complex and another as membrane-associated enzyme.

In this report, a genome-scale reconstruction of Bacillus subtilis metabolism and its iterative development based on the combination of genomic, biochemical, and physiological information and high-throughput phenotyping experiments is presented. The initial reconstruction was converted into an in silico model and expanded in a four-step iterative fashion. First, network gap analysis was used to identify 48 missing reactions that are needed for growth but were not found in the genome annotation. Second, the computed growth rates under aerobic conditions were compared with high-throughput phenotypic screen data, and the initial in silico model could predict the outcomes qualitatively in 140 of 271 cases considered. Detailed analysis of the incorrect predictions resulted in the addition of 75 reactions to the initial reconstruction, and 200 of 271 cases were correctly computed. Third, in silico computations of the growth phenotypes of knock-out strains were found to be consistent with experimental observations in 720 of 766 cases evaluated. Fourth, the integrated analysis of the large-scale substrate utilization and gene essentiality data with the genome-scale metabolic model revealed the requirement of 80 specific enzymes (transport, 53; intracellular reactions, 27) that were not in the genome annotation. Subsequent sequence analysis resulted in the identification of genes that could be putatively assigned to 13 intracellular enzymes. The final reconstruction accounted for 844 open reading frames and consisted of 1020 metabolic reactions and 988 metabolites. Hence, the in silico model can be used to obtain experimentally verifiable hypothesis on the metabolic functions of various genes.

In this study, persulfate, a solid-type oxidant, was adopted as a substitute for hydrogen peroxide in extracting lipid from microalgae biomass. Microalgae cells were concentrated at pH 3 and with 200mg/L of ferric chloride, conditions which can activate oxidants such as hydrogen peroxide and persulfate. At a persulfate concentration of 2mM and a reaction temperature of 90°C, exceedingly high extraction efficiency over 95% was obtained, which was higher than with 0.5% hydrogen peroxide at the same temperature. This result showed that persulfate is sufficiently powerful and incomparably cheap enough to replace the potent yet expensive oxidant. It appears that combining iron-based coagulation and persulfate-based lipid extraction is indeed a competitive approach that can possibly lighten the process burden for the microalgae-derived biodiesel production.

Exploitation of magnetic flocculants is regarded as a very promising energy-saving approach to microalgae harvesting. However, its practical applicability remains limited, mainly because of the problem of the postharvest separation of magnetic flocculants from microalgal flocs, which is crucial both for magnetic-flocculant recycling and high-purity microalgal biomasses, but which is also a very challenging and energy-consuming step. In the present study, we designed magnetic nanoflocculants dually functionalizable by two different organosilane compounds, (3-aminopropyl)triethoxysilane (APTES) and octyltriethoxysilane (OTES), which flocculate negatively charged microalgae and are readily detachable at the water-nonpolar organic solvent (NOS) interface only by application of an external magnetic field. APTES functionalization imparts a positive zeta potential charge (29.6 mV) to magnetic nanoflocculants, thereby enabling microalgae flocculation with 98.5% harvesting efficiency (with a dosage of 1.6 g of dMNF/g of cells). OTES functionalization imparts lipophilicity to magnetic nanoflocculants to make them compatible with NOS, thus effecting efficient separation of magnetic flocculants passing through the water-NOS interface sieve from hydrophilic microalgae. Our new energy-saving approach to microalgae harvesting concentrates microalgal cultures (∼1.5 g/L) up to 60 g/L, which can be directly connected to the following process of NOS-assisted wet lipid extraction or biodiesel production, and therefore provides, by simplifying multiple downstream processes, a great potential cost reduction in microalgae-based biorefinement.

Semipermeable microcapsules are appealing for controlled release of drugs, study of cell-to-cell communication, and isolation of enzymes or artificial catalysts. Here, we report a microfluidic strategy for creating monodisperse microcapsules with size-selective permeability using polymerization-induced phase separation. Monodisperse water-in-oil-in-water (W/O/W) double-emulsion drops, whose ultrathin middle layer is composed of photocurable resin and inert oil, are generated in a capillary microfluidic device, and irradiated by UV light. Upon UV illumination, the monomers are photopolymerized, which leads to phase separation between the polymerized resin and the oil within the ultrathin shell. Subsequent dissolution of the oil leaves behind regular pores in the polymerized membrane that interconnect the interior and exterior of the microcapsules, thereby providing size-selective permeability. The degree of phase separation can be further tuned by adjusting the fraction of oil in the shell or the affinity of the oil to the monomers, thereby enabling the control of the cutoff value of permeation. High mechanical stability and chemical resistance of the microcapsules, as well as controllable permeability and high encapsulation efficiency, will provide new opportunity in a wide range of applications.

To overcome fouling issue in membrane-based algae harvesting and thus make an otherwise promising harvesting option more competitive, a bubble-generator plate was developed. According to computational fluid dynamics analysis, the plate generated substantial hydrodynamic power in terms of high pressure, velocity, and shear stress. When installed in a membrane filtration system with membranes of different surface and structural characteristics (one prepared by the phase inversion method, and a commercial one) the bubble-generator was indeed effective in reducing fouling. Without the plate, the much cheaper homemade membrane had the similar performance as the commercial one. Use of the bubble-generator considerably improved the performance of both membranes, and revealed a valuable synergy with the asymmetrical structure of the homemade membrane. This result clearly showed that the ever-problematic fouling could be mitigated in a rather easy manner, and in so doing, that membrane technology could indeed become a practical option for algae harvesting.

Converting lipid-extracted microalgal wastes to methane (CH4) via anaerobic digestion (AD) has the potential to make microalgae-based biodiesel platform more sustainable. However, it is apparent that remaining n-hexane (C6H14) from lipid extraction could inhibit metabolic pathway of methanogens. To test an inhibitory influence of residual n-hexane, this study conducted a series of batch AD by mixing lipid-extracted Chlorella vulgaris with a wide range of n-hexane concentration (∼10 g chemical oxygen demand (COD)/L). Experimental results show that the inhibition of n-hexane on CH4 yield was negligible up to 2 g COD/L and inhibition to methanogenesis became significant when it was higher than 4 g COD/L based on quantitative mass balance. Inhibition threshold was about 4 g COD/L of n-hexane. Analytical result of microbial community profile revealed that dominance of alkane-degrading sulfate-reducing bacteria (SRB) and syntrophic bacteria increased, while that of methanogens sharply dropped as n-hexane concentration increased. These findings offer a useful guideline of threshold n-hexane concentration and microbial community shift for the AD of lipid-extracted microalgal wastes.

A yeast strain utilizing styrene epoxide as a sole carbon and energy source was isolated from soil samples for the production of enantiopure of styrene epoxide by kinetic resolution. The strain, identified as a Rhodosporidium toruloides SJ-4, expressed an epoxide hydrolase which preferentially converted (R)-styrene epoxide into the corresponding diol. A maximum activity of 135 U/L was observed when biomass (dry cell mass) reached 6.7 g/L at 21 h of batch culture. Under the partially optimized reaction conditions ( and pH 8.0), the optically pure (S)-styrene epoxide was obtained with the yield of 21% when the initial substrate concentration was 100 mM. The reaction was completed at 9 h.

Caseinomacropeptide is a polypeptide of 64 amino acid residues (106-169) derived from the C-terminal part of the mammalian milk k-casein. This macropeptide has various biological activities and is used as a functional food ingredient as well as a pharmaceutical compound. The gene encoding the human caseinomacropeptide (hCMP) was synthesized and expressed with an alpha-factor secretion signal in the two yeast strains, Saccharomyces cerevisiae and Pichia pastoris. The complete polypeptide of the recombinant hCMP was produced and secreted in a culture medium by both the strains, but the highest production was observed in S. cerevisiae with a galactose-inducible promoter. In a fed-batch bioreactor culture, 2.5 g/l of the recombinant hCMP was obtained from the S. cerevisiae at 97 h.

Caseinomacropeptide (CMP) is a glycopeptide of 64 amino acid residues derived from theC-terminal of mammalian milkk-casein. Recently, human CMP (hCMP) was produced from the recombinant yeastSaccharomyces cerevisiae. In this study, the antiobesity activity of the recombinant hCMP (rhCMP) was investigatedin vivo using Sprague-Dawley rats. The rhCMP did not affect the rats fed with a normal fat diet (fat content, 5.0%), but decreased the body weight gain of the rats fed with a high fat diet (fat content, 20%) by up to 19%. Autopsies revealed that the weights of the liver, kidney and adipose tissues decreased when the rats were given the rhCMP, which also reduced the lipid concentrations in the plasma and liver, but enhanced the fecal excretion of lipids. These results suggest that rhCMP prevent the accumulation of lipid by stimulating its fecal excretion, so could be used as a food supplement to alleviate the obesity problem caused by a high fat diet.

A reactor-scale hydrogen (H2) productionvia the water-gas shift reaction of carbon monoxide (CO) and water was studied using the purple nonsulfur bacterium,Rhodopseudomonas palustris P4. The experiment was conducted in a two-step process: an aerobic/chemoheterotrophic cell growth step and a subsequent anaerobic H2 production step. Important parameters investigated included the agitation speed, inlet CO concentration and gas retention time. P4 showed a stable H2 production capability with a maximum activity of 41 mmol H2 g cell−1h−1 during the continuous reactor operation of 400 h. The maximal volumetric H2 production rate was estimated to be 41 mmol H2 L1h−1, which was about nine-fold and fifteen-fold higher than the rates reported for the photosynthetic bacteriaRhodospirillum rubrum andRubrivivax gelatinosus, respectively. This is mainly attributed to the ability of P4 to grow to a high cell density with a high specific H2 production activity. This study indicates that P4 has an outstanding potential for a continuous H2 productionvia the water-gas shift reaction once a proper bioreactor system that provides a high rate of gas-liquid mass transfer is developed.

The testing samples in this experiment were obtained from an acrylic fibre manufacturing companys industrial wastewater. The water was the waste of the acrylic polymerization process. The company is located in Ulsan, Korea. The concentration of acrylonitrile (AN) in the wastewater was about 25–35 mg/L. Concentrations of 3–10 mg/ L of methyl acrylate (M-35) were also found. The samples were treated by the TiO2/UV system and were analyzed to determine the values of CODcr, ammonia, nitrite nitrogen, and nitrate nitrogen by using an Auto Analyzer (Bran+ Luebbe, Germany) and a TOC (Tekmar Dohrmann, USA). Various reaction parameters, such as TiO2 content, light intensity and wavelength, and the number of UV lamps were varied and their effects or decomposition efficiency were analyzed. The adsorption onto TiO2 surfaces by organic materials in the wastewater was negligible. The reaction-rate constant was also calculated. The reaction rate constant for the G36T6L lamp at both 185 nm and 256 nm was 0.0661 hr-1 which is 1.3 times higher than that of the TUV36T5 lamp at 256 nm. While the reaction rate was increased by increasing the surface area of the photocatalyst, the excess photocatalyst blocked the light sources, causing a photoenclosure effect. The stability of the treated wastewater was greatly increased because the elimination of the concentration of nitrite was followed by an increase in the concentration of nitrate. Generally, the ratio of BOD5/CODcr is used as the criterion for determining biodegradability. A ratio of 0.3 is needed for biological degradation. The ratio of the treated wastewater increased to 0.5 after 12 hours of reaction. The ratio increased to 0.8 after 20 hours.

A recombinant yeast Pichia pastoris carrying the gene encoding epoxide hydrolase (EH) of Rhodotorula glutinis was constructed and used for producing (S)-styrene oxide by enantioselective hydrolysis of racemic mixtures of styrene oxides. The EH gene was obtained by PCR amplification of cDNA of R. glutinis and integrated into the chromosomal DNA of P. pastoris to express EH under the control of AOX promoter. The recombinant yeast has a high hydrolytic activity toward (R)-styrene oxide as 358 nmol min−1 (mg cell)−1, which is about 10-fold higher than that of wild type R. glutinis. When kinetic resolution was conducted by the recombinant yeast at a high initial epoxides concentration of 526 mM that constitutes an epoxide–water two-liquid phase, chiral (S)-styrene oxide with an enantiomeric excess (e.e.) higher than 98% was obtained as 36% yield (theoretical, 50%) at 16 h.

Textile wastewater from the Pusan Dyeing Industrial Complex (PDIC) was treated utilizing a two-stage continuous system, composed of an upflow anaerobic sludge blanket reactor and an activated sludge reactor. The effects of color and organic loading rates were studied by varying the hydraulic retention time and influent glucose concentration. The maximum color load to satisfy the legal discharge limit of color intensity in Korea (400 ADMI, unit of the American Dye Manufacturers Institute) was estimated to be 2,700 ADMI·L−1 day−1. This study indicates that the two-stage anaerobic/aerobic reaction system is potentially useful in the treatment of textile wastewater.

Photocatalytic degradation of organic contaminants in wastewater by TiO2 has been introduced in both bench and pilot-scale applications in suspended state or immobilized state on supporting material. TiO2 in suspended state gave less activity due to its coagency between particles. Recent advances in environmental photocatalysis have focused on enhancing the catalytic activity and improving the performance of photocatalytic reactors. This paper reports a preliminary design of a new immobilized TiO2 photocatalyst and its photocatalytic fluidized bed reactor (PFBR) to apply photochemical degradation of a dye, Rhodamine B (RhB). But it was not easy to make a cost-effective and well activated immobilized TiO2 particles. A kind of photocatalyst (named Photomedium), consisting of hollow ceramic balls coated with TiO2-sol, which was capable of effective photodegradation of the dye, has been presented in this study. The photocatalytic oxidation of RhB was investigated by changing Photomedia concentrations, initial RhB concentrations, and UV intensity in PFBR

A newly isolated Citrobacter sp. Y19 for CO-dependent H 2 production was studied for its capability of fermentative H 2 production in batch cultivation. When glucose was used as carbon source, the pH of the culture medium significantly decreased as fermentation proceeded and H 2 production was seriously inhibited. The use of fortified phosphate at 60– 180 mM alleviated this inhibition. By increasing culture temperatures (25–36°C), faster cell growth and higher initial H 2 production rates were observed but final H 2 production and yield were almost constant irrespective of temperature. Optimal specific H 2 production activity was observed at 36°C and pH 6–7. The increase of glucose concentration (1– 20 g/l ) in the culture medium resulted in higher H 2 production, but the yield of H 2 production (mol H 2 /mol glucose) gradually decreased with increasing glucose concentration. Carbon mass balance showed that, in addition to cell mass, ethanol, acetate and CO 2 were the major fermentation products and comprised more than 70% of the carbon consumed. The maximal H 2 yield and H 2 production rate were estimated to be 2.49 mol H 2 / mol glucose and 32.3 mmol H 2 / g cell h , respectively. The overall performance of Y19 in fermentative H 2 production is quite similar to that of most H 2 -producing bacteria previously studied, especially to that of Rhodopseudomonas palustris P4, and this indicates that the attempt to find an outstanding bacterial strain for fermentative H 2 production might be very difficult if not impossible.

H2-producing bacteria were isolated from anaerobic granular sludge. Out of 72 colonies (36 grown under aerobic conditions and 36 under anaerobic conditions) arbitrarily chosen from the agar plate cultures of a suspended sludge, 34 colonies (15 under aerobic conditions and 19 under anaerobic conditions) produced H2 under anaerobic conditions. Based on various biochemical tests and microscopic observations, they were classified into 13 groups and tentatively identified as follows: From aerobic isolates,Aeromonas spp. (7 strains),Pseudomonas spp. (3 strains), andVibrio spp. (5 strains); from anaerobic isolates,Actinomyces spp. (11 strains),Clostridium spp. (7 strains), andPorphyromonas sp. When glucose was used as the carbon substrate, all isolates showed a similar cell density and a H2 production yield in the batch cultivations after 12h (2.24–2.74 OD at 600 nm and 1.02–1.22 mol H2/mol glucose, respectively). The major fermentation by-products were ethanol and acetate for the aerobic isolates, and ethanol, acetate and propionate for the anaerobic isolates. This study demonstrated that several H2 producers in an anaerobic granular sludge exist in large proportions and their performance in terms of H2 production is quite similar.

A newly isolated Rhodopseudomonas palustris P4 for CO-dependent H2 production was studied for its capability of fermentative H2 production in batch cultivations. Important parameters investigated include pH, temperature, concentrations of phosphate and glucose, intermittent purging of culture broth by argon gas, and kind of sugars. The pH of the culture medium significantly decreased as fermentation proceeded due to the accumulation of various organic acids, and this inhibited the H2 production seriously. The use of fortified phosphate at 60– 300 mM could alleviate this inhibition. The increase of glucose concentration (1– 20 g / l ) resulted in higher H2 production, but the yield of H2 production (mmol H2/mmol glucose) gradually decreased with increasing glucose concentration. Intermittent purging of the culture broth by argon gas improved H2 production. Carbon mass balance showed that, in addition to cell mass, ethanol, acetate and CO2 were the major fermentation products that comprised more than 70% of carbon consumed. R. palustris P4 could utilize various monosaccharides (glucose, galactose, fructose), disaccharides (lactose, sucrose) and starch to produce H2. However, the H2 production rate with disaccharides and starch was much slower than that with monosaccharides. The maximal H2 yield and H2 production rate were estimated to be 2.76 mmol H2/mmol glucose and 29.9 mmol H2/g cell h, respectively. These results indicate that, although isolated for CO-dependent H2 production, R. palustris P4 has a high potential as a fermentative H2 producer.

In this study, ferric chloride (FeCl3) was used to integrate downstream processes (harvesting, lipid extraction, and esterification). At concentration of 200 mg/L and at pH 3, FeCl3 exhibited an expected degree of coagulation and an increase in cell density of ten times (170 mg/10 mL). An iron-mediated oxidation reaction, Fenton-like reaction, was used to extract lipid from the harvested biomass, and efficiency of 80% was obtained with 0.5% H2O2 at 90 °C. The iron compound was also employed in the esterification step, and converted free fatty acids to fatty acid methyl esters under acidic conditions; thus, the fatal problem of saponification during esterification with alkaline catalysts was avoided, and esterification efficiency over 90% was obtained. This study clearly showed that FeCl3 in the harvesting process is beneficial in all downstream steps and have a potential to greatly reduce the production cost of microalgae-originated biodiesel.

Among the various steps entailed in the production of biodiesel from microalgae, the efficiency and cost-reduction of the cultivation and harvesting steps remain key obstacles to its practical commercialization. Recently, in order to overcome the technical bottlenecks and limitations with regard to both steps, nanoparticle engineering based on particles' unique physico-chemical and mechanical properties has been extensively applied as a powerful analytical and practical tool. These applications include the enhancement of cell growth and/or pigments by light back-scattering, the induction of intracellular lipid accumulation by nutritional competition and/or stress environment, the improvement of cell separation efficiency and processing time from culture broth, the multiple reuse of magnetic nanoparticle flocculant, and integrated one-pot harvesting/cell-disruption. This review presents and discusses the recent nanoparticle-engineering-based developments in the implementation of practical microalgal cultivation and harvesting processes.

Natural calcium carbonate-based nanocomposites often have superior physical properties and provide a comprehensive source for bioinspired synthetic materials. Here we present thermodynamically stable, transparent CaCO3 microlens arrays (MLA) produced by transforming an amorphous CaCO3 phase into nanocrystalline calcite. We analyze the structure and properties of crystallized MLA by X-ray scattering, transmitted and polarized light microscopy, and electron microscopy and find that MLA are crystallized in spherulite-like patterns without changing the shape of the microlens. The key finding is that nanocrystallinity of the calcite formed diminishes structural anisotropy on the wavelength scale and results in greatly reduced birefringent effects. The remnant preferred orientation of the optical axes of calcite crystals in the plane of the microlens arrays leads to some directionality of optical properties, which may be beneficial for technical applications.

Industrial CO2-rich flue-gases, owing to their eco-toxicity, have yet to be practically exploited for microalgal biomass and lipid production. In this study, various autotrophic and mixotrophic culture modes for an oleaginous microalga, Chlorella sp. KR-1 were compared for the use in actual coal-fired flue-gas. Among the mixotrophic conditions tested, the fed-batch feedings of glucose and the supply of air in dark cycles showed the highest biomass (561 mg/L d) and fatty-acid methyl-ester (168 mg/L d) productivities. This growth condition also resulted in the maximal population of microalgae and the minimal population and types of KR-1-associated-bacterial species as confirmed by particle-volume-distribution and denaturing-gradient-gel-electrophoresis (DGGE) analyses. Furthermore, microalgal lipid produced was assessed, based on its fatty acid profile, to meet key biodiesel standards such as saponification, iodine, and cetane numbers.

In this article, we report the preparation, characterization and microalgae recovery potential of a new family of fouling-resistant polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes embedded with hydrophilic and PEGylated polymeric particles. To optimize membrane performance for microalgae harvesting, we investigate the effects of three hydrophilic additives (Pluronic F-127, polyvinylpyrrolidone and polyethylene glycol) on the morphology, pore size, bulk composition, surface composition, wettability and surface charge, flux and fouling resistance of the mixed matrix PVDF membranes with in situ PEGylated polyethyleneimine (PEI) particles. Our filtration experiments show that a mixed matrix PVDF membrane with PEGylated PEI particles and Pluronic F-127 additive (PNSM-1) has an algae retention of 100% with a permeate flux of 96 L/m 2 /hr that is larger (by ∼50%) than that of a commercial and hydrophilic PVDF UF membrane with a molecular weight cut-off of 30 kDa using a suspension of Chlorella sp. KR-1 microalgae with 1.2–1.4 g/L of dry biomass. The algae and water flux recovery rates of our new PNSM-1 are equal to∼ 94% and 100%, respectively, following a simulated membrane wash with deionized water and two subsequent water and microalgae filtration cycles.