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This study examined the feasibility of using an algal-bacterial process for removal of phenol and NH 4 + -N from differently diluted coke wastewater with simultaneous production of biomass. Under illumination, microalgal-bacterial (MSB) cultures performed complete phenol degradation at all dilutions of coke wastewater while sole microalgal culture (MSA) degraded a maximum of 27.3% of phenol (initial concentration: 24.0mgL -1 ) from 5-fold diluted wastewater. Furthermore, the MSB culture had the highest rate of NH 4 + -N removal (8.3mgL -1 d -1 ) and fatty acid production (20mgL -1 d -1 ) which were 2.3- and 1.5-fold higher than those observed in the MSA cultures, probably due to decreases in toxic organic pollutants. Multivariate analyses indicated that co-cultivation of activated sludge was directly correlated with the elevated removals of phenol and NH 4 + -N. In the presence of sludge, adequate dilution of the coke wastewater can maximize the effect of bacteria on NH 4 + -N removal and biomass production., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

For the efficient separation of lipid extracted from microalgae cells, a novel membrane was devised by introducing a functional polymer coating onto a membrane surface by means of an initiated chemical vapor deposition (iCVD) process. To this end, a steel-use-stainless (SUS) membrane was modified in a way that its surface energy was systemically modified. The surface modification by conformal coating of functional polymer film allowed for selective separation of oil-water mixture, by harnessing the tuned interfacial energy between each liquid phase and the membrane surface. The surface-modified membrane, when used with chloroform-based solvent, exhibited superb permeate flux, breakthrough pressure, and also separation yield: it allowed separation of 95.5 ± 1.2% of converted lipid (FAME) in the chloroform phase from the water/MeOH phase with microalgal debris. This result clearly supported that the membrane-based lipid separation is indeed facilitated by way of membrane being functionalized, enabling us to simplify the whole downstream process of microalgae-derived biodiesel production.

In this study, we attempted to understand signaling pathways behind lipid biosynthesis by employing a chemical genetics approach based on small molecule inhibitors. Specific signaling inhibitors of MAP kinase or modulators of cAMP signaling were selected to evaluate the functional roles of each of the key signaling pathways in three different microalgal species: Chlamydomonas reinhardtii, Chlorella vulgaris, and Haematococcus pluvialis. Our results clearly indicate that cAMP signaling pathways are indeed positively associated with microalgal lipid biosynthesis. In contrast, MAP kinase pathways in three microalgal species are all negatively implicated in both lipid and carotenoid biosynthesis.

Open raceway ponds are cost-efficient for mass cultivation of microalgae compared with photobioreactors. Although low-cost options like wastewater as nutrient source is studied to overcome the commercialization threshold for biodiesel production from microalgae, a cost analysis on the use of wastewater and other incremental increases in productivity has not been elucidated. We determined the effect of using wastewater and wavelength filters on microalgal productivity. Experimental results were then fitted into a model, and cost analysis was performed in comparison with control raceways. Three different microalgal strains, Chlorella vulgaris AG10032, Chlorella sp. JK2, and Scenedesmus sp. JK10, were tested for nutrient removal under different light wavelengths (blue, green, red, and white) using filters in batch cultivation. Blue wavelength showed an average of 27% higher nutrient removal and at least 42% higher chemical oxygen demand removal compared with white light. Naturally, the specific growth rate of microalgae cultivated under blue wavelength was on average 10.8% higher than white wavelength. Similarly, lipid productivity was highest in blue wavelength, at least 46.8% higher than white wavelength, whereas FAME composition revealed a mild increase in oleic and palmitic acid levels. Cost analysis reveals that raceways treating wastewater and using monochromatic wavelength would decrease costs from 2.71 to 0.73 $/kg biomass. We prove that increasing both biomass and lipid productivity is possible through cost-effective approaches, thereby accelerating the commercialization of low-value products from microalgae, like biodiesel.

In this study, lipid extraction from Aurantiochytrium sp. was performed using a molten-salt/ionic-liquid mixture. The total fatty acid content of Aurantiochytrium sp. was 478.8 mg/g cell, from which 145 mg/g cell (30.3% of total fatty acids) of docosahexaenoic acid (DHA) was obtained. FeCl3·6H2O showed a high lipid extraction yield (207.9 mg/g cell), when compared with that of [Emim]OAc, which was only 118.1 mg/g cell; notably however, when FeCl3·6H2O was mixed with [Emim]OAc (5:1, w/w), the yield was increased to 478.6 mg/g cell. When lipid was extracted by the FeCl3·6H2O/[Emim]OAc mixture at a 5:1 (w/w) blending ratio under 90 °C, 30 min reaction conditions, the fatty acid content of the extracted lipid was a high purity 997.7 mg/g lipid, with most of the DHA having been extracted (30.2% of total fatty acids). Overall, lipid extraction from Aurantiochytrium sp. was enhanced by the synergistic effects of the molten-salt/ionic-liquid mixture with different ions.

The present study assessed the use of hydrolysate of lipid extracted algal biomass (LEA) combined with the sugar factory wastewater (SFW) as a low cost nutrient and a carbon source, respectively for microalgal cultivation. Microalgal strain Ettlia sp. was both mixotrophically and heterotrophically cultivated using various amounts of hydrolysate and SFW. The culture which was grown in medium containing 50% LEA hydrolysate showed highest growth, achieving 5.26 ± 0.14 gL(-1) after 12 days of cultivation. The addition of SFW increased the lipid productivity substantially from 5.8 to 95.5 mg L(-1)d(-1) when the culture medium was fortified with 20% SFW. Gas chromatography analysis indicated a noticeable increase of 20% in C16 and C18 fraction in FAME distribution under above condition. Therefore, it can be concluded that the combination of LEA hydrolysate and sugar factory waste water can be a powerful growth medium for economical algal cultivation., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

In this work, a cooperative algal-bacterial system that efficiently degrades thiocyanate (SCN(-)), a toxic contaminant, and exhibits high lipid productivity, was developed. A consortium of mixed bacteria (activated sludge) and microalgae was sequentially cultivated under photoautotrophic and photoheterotrophic modes. The hydrolysis of SCN(-) to ammonium (NH4(+))-nitrogen and subsequent nitrification steps were performed by the initial activated sludge under lithoautotrophic conditions. The NH4(+) and oxidized forms of nitrogen, nitrite (NO2(-)) and nitrate (NO3(-)), were then assimilated and removed by the microalgal cells when light was supplied. After the degradation of SCN(-), the cultivation mode was changed to photoheterotrophic conditions in a sequential manner. Algal-bacterial cultures containing Chlorella protothecoides and Ettlia sp. yielded significantly increased lipid productivity under photoheterotrophic conditions compared to photoautotrophic conditions (28.7- and 17.3-fold higher, respectively). Statistical methodologies were also used to investigate the effects of volatile fatty acids and yeast extract on biomass and lipid production., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Identification of novel microalgal strains with high lipid productivity is one of the most important research topics in renewable biofuel research. However, the major bottleneck in the strain screening process is that currently known methods for the estimation of microalgal lipid are laborious and time-consuming. The present study successfully employed sulpho-phospho-vanillin (SPV) colorimetric method for direct quantitative measurement of lipids within liquid microalgal culture. The SPV reacts with lipids to produce a distinct pink color, and its intensity can be quantified using spectrophotometric methods by measuring absorbance at 530nm. This method was employed for a rapid quantification of intracellular lipid contents within Chlorella sp., Monoraphidium sp., Ettlia sp. and Nannochloropsis sp., all of which were found to have lipid contents ranging in between 10% and 30%. Subsequent analysis of the biomass using gas chromatography confirmed that our protocol is highly accurate (R(2)=0.99)., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Despite receiving increasing attention during the last few decades, the production of microalgal biofuels is not yet sufficiently cost-effective to compete with that of petroleum-based conventional fuels. Among the steps required for the production of microalgal biofuels, the harvest of the microalgal biomass and the extraction of lipids from microalgae are two of the most expensive. In this review article, we surveyed a substantial amount of previous work in microalgal harvesting and lipid extraction to highlight recent progress in these areas. We also discuss new developments in the biodiesel conversion technology due to the importance of the connectivity of this step with the lipid extraction process. Furthermore, we propose possible future directions for technological or process improvements that will directly affect the final production costs of microalgal biomass-based biofuels., (Copyright © 2013 Elsevier Inc. All rights reserved.)

This study describes the development of a microfluidic device for the high-throughput screening of culture conditions, such as the optimum sodium acetate concentration for promoting rapid growth and high lipid accumulation of Chlamydomonas reinhardtii. An analysis of the microalgal growth on the microfluidic device revealed an optimum sodium acetate concentration of 5.72 g L(-1). The lipid content, determined by the 4,4-Difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY® 505/515) staining method, increased with the sodium acetate concentration. The results were found to be statistically reproducible with respect to cell growth and lipid production. Other nutrient conditions, including the nitrogen and phosphorus concentrations, can also be optimized on the same microfluidic platform. The microfluidic device performance results agreed well with the results obtained from the flask-scale experiments, validating that the culture conditions were scalable. Finally, we, for the first time, established a method for the absolute quantification of the microalgal lipid content in the picoliter culture volumes by comparing the on-chip and off-chip data. In conclusion, we successfully demonstrated the high-throughput screening of sodium acetate concentrations that induced high growth rates and high lipid contents in C. reinhardtii cells on the microfluidic device.

In this study, proteomic approach was employed to advance our understanding of genes associated with microalgal lipid production. We first generated random mutants of Chlamydomonas reinhardtii, which displayed increased or decreased lipid content, compared to that in the wild-type. Mutants were designated as CR12 and CR48. Then, the changes of protein expression associated with the mutations of Chlamydomonas reinhardtii were analyzed. We could identify proteins that were significantly up-regulated or down-regulated either in the wild-type or CR12 or CR48. Our results will help understand additional genes or pathways directly or indirectly linked to microalgal lipid production., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The oleaginous microalga Aurantiochytrium sp. KRS101 was cultivated in enzymatic hydrolysates of alkali-pretreated empty palm fruit bunches (EFBs), without prior detoxification process. The maximal levels of lipid and docosahexaenoic acid synthesized were 12.5 and 5.4 g L⁻¹ after cultivation for 36 h. Similar lipid levels were also obtained via simultaneous saccharification and cultivation. The results suggested that EFB is a promising source for production of useful lipids by the microalgal strain.

A comparative study of Chlamydomonas reinhardtii wild type CC124 and a cell wall-less mutant sta6-1 is described using FACS in conjunction with two different lipophilic fluorescent dyes, Nile Red and BODIPY 505/515. The results indicate that BODIPY 505/515 is more effective for the vital staining of intracellular lipid bodies and single cell sorting than Nile Red. While BODIPY 505/515 stained cells continued to grow after single cell sorting using FACS, Nile Red stained cells failed to recover from sorting. In addition, a comprehensive study was performed to establish a quantitative baseline for future studies for either lipid accumulation and/or microalgal growth by measuring various parameters such as cell count, size, fatty acid contents/composition, and optical/confocal images of the wild type and mutant., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A cultivation system in the two-stage photoautotrophic-photoheterotrophic/mixotrophic mode was adapted to maximize lipid productivity of two freshwater strains of Chlorella sp. grown in brewery wastewater (BWW). The endogenous Chlorella sp. isolated from BWW had a higher growth rate than wild-type Chlorella vulgaris (UTEX-265) while C. vulgaris (UTEX-265) had a higher maximal biomass and lipid contents than that of endogenous Chlorella sp., resulting in more than 90% of the inorganic nutrients in both total nitrogen (TN) and phosphorus (TP) was removed during the first stage in the two-stage photoautotrophic-photoheterotrophic mode in each Chlorella sp. The maximal biomass and lipid contents of C. vulgaris (UTEX-265) for single stage photoautotrophic cultivation were 1.5 g/L and 18%, respectively. Importantly, during two-stage photoautotrophic-photoheterotrophic cultivation for C. vulgaris (UTEX-265), the biomass was increased to 3.5 g/L, and the lipid productivity was increased from 31.1 to 108.0mg/L day., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

High-cost downstream process is a major bottleneck for producing microalgal biodiesel at reasonable price. Conventional lipid extraction process necessitates biomass drying process, which requires substantial amount of energy. In this regard, lipid extraction from wet biomass must be an attractive solution. However, it is almost impossible to recover lipid directly from wet microalgae with current technology. In this study, we conceived osmotic shock treatment as a novel method to extract lipid efficiently. Osmotic shock treatment was applied directly to wet Chlamydomonas reinhardtii biomass with water content >99%, along with both polar and non-polar organic solvents. Our results demonstrated that osmotic shock could increase lipid recovery approximately 2 times. We also investigated whether the presence of cell wall or different cell stages could have any impact on lipid recovery. Cell wall-less mutant stains and senescent cell phase could display significantly increased lipid recovery. Taken together, our results suggested that osmotic shock is a promising technique for wet lipid extraction from microalgal biomass and successfully determined that specific manipulation of biomass in certain cell phase could enhance lipid recovery further., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

As energy and environment have become urgent issues, there has been increasing needs to develop alternative energy source, such as microalgal bio-fuel. In this study, we investigated the growth and lipid contents of microalgae Nannochloris oculata under various environmental conditions for biodiesel production. Our results indicated that biomass productivities of N. oculata were correlated with increasing nitrogen concentrations up to 37.5 ppm. High irradiance using 230-250 μmol/m(2) led to higher biomass yields than low irradiance of 160-180 μmol/m(2). Biomass productivities increased further by manipulating surface to volume ratio (S/V), which in turn enhanced light penetration. Finally, optimal biomass productivities (1.04 g/l day) could be achieved by the supplementation of yeast extract. Lipid contents and fatty acid profiles of N. oculata were affected by the different growth conditions. Lipid contents of N. oculata decreased as nitrogen concentration increased. Lower temperature (15 °C) resulted in higher lipid content than higher temperature (25 °C). Fatty acid profiles of N. oculata indicated that palmitic acid (C16:0) and linoleic acid (C18:2) were the two most abundant fatty acids, but the supplementation of yeast extract increased linolenic acid (C18:3) content. Our results suggested the feasibility of N. oculata for the biodiesel production.

In order to increase the economic feasibility of biodiesel production from microalgae, the residual biomass after biodiesel production can be utilized as biosorbent for heavy metal removal. In this study, biosorption of chromium by residual Nannochloris oculata after lipid extraction was investigated. Increased surface area of N. oculata was observed after lipid extraction. Cr(III) removal increased as the pH increased from 2 to 6, while Cr(VI) removal was highest at pH 2 and it decreased with the increase in pH. Cr(VI) was reduced to Cr(III) in the presence of biomass under acidic conditions; X-ray photoelectron spectroscopy revealed that the converted Cr(III) was bound to the biomass. Chromium removal was significantly enhanced at high chromium concentrations, which indicates that surface reactions may occur at high chromium/biomass ratios. FTIR study indicated that phosphate and carboxyl functional groups of the biomass were mainly responsible for chromium binding., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The large water footprint is one of the major bottlenecks for the sustainable microalgae-based biorefinery. In order to reduce the amount of water that is needed for mass cultivation of microalgae, the reusability of culture medium for further algal growth was tested. Chlorella vulgaris was cultivated in recycled medium that was obtained from harvesting microalgal cells by using either centrifugation or flocculation with FeCl 3 or alum. The present study shows that centrifugation and flocculation with FeCl 3 are equally effective (> 90%) for harvesting C. vulgaris without any deleterious effects on algal growth when recycled media was used. However, even low concentration (< 5 ppm) of residual alum was shown to inhibit microalgal growth. More interestingly, the recycled media obtained after centrifugation or flocculation with FeCl 3 had a positive effect on biomass and lipid productivity of C. vulgaris . Extracellular substances such as carbohydrate, proteins, or ferric ions in the recycled media appear to cause these positive effects. Furthermore, change of pH to 2–3 and washing with water were found to effectively remove the residual ferric ions that are present in either harvested biomass or biodiesel, respectively. These results suggest that the use of recycled medium for microalgal cultivation is possible, and the choice of harvest methods must be carefully made when the recycling of culture medium is considered for microalgal cultivation. [ABSTRACT FROM AUTHOR]

While the potential of hydrothermal liquefaction (HTL) of microalgae to produce biocrude regardless of the types of microalgae (biomass-agnostic) has been noted, the quality of biocrude and the Energy Return On Investment (EROI) of HTL of various microalgal species have not been compared in detail. Here we report that the quality of biocrude and the EROI of microalgal HTL are directly dependent on the lipid contents of microalgae. When Nannochloropsis oceanica (30.2% lipid content) and Golenkinia sp. (17.3% lipid content) were compared for the quality of HTL in terms of the total yield, asphaltene/non-asphaltene contents, heteroatom (O, N, and S) concentrations, and the effective hydrogen-to-carbon ratios (H/C eff ) of the biocrudes, N. oceanica with high lipid content produced biocrude that can be more suitable for catalytic upgrading to transportation fuels than the biocrude from Golenkinia sp. with low lipid content. HTL of N. oceanica at low temperature (200 °C) in particular produced the biocrude with EROI that was better than that of Golenkinia sp. These results strongly support that the choice of microalgae with high lipid content is still a key factor that must be considered for biocrude production as much as it is regarded important for biodiesel production using microalgal biomass. [ABSTRACT FROM AUTHOR]

Highlights: [•] Acid-catalyzed hot-water treatment for lipid extraction from wet microalgae. [•] The optimal lipid-extraction condition of 1.00% sulfuric acid concentration. [•] Extraction of docosahexaenoic acid (DHA)-rich lipids from Aurantiochytrium sp. [Copyright &y& Elsevier]

Highlights: [•] Structural correlation between cellular development and lipid body accumulation. [•] HTP screening of thraustochytrid using FACS with different fluorescent dyes. [•] Found that BODIPY 505/515 with less concentration of DMSO effective for FACS. [•] Established a quantitative baseline for lipids accumulation and/or microalgal growth. [Copyright &y& Elsevier]

Highlights: [•] Degrading the thiocyanate (SCN−) and producing lipids were achieved by mixed culture. [•] Two-mode was sequentially employed: a lithoauto- and photoautotrophic mode. [•] Oxidized nutrients from SCN− hydrolysis were utilized by photoautotrophic consortium. [•] The obtained mixed culture performed high self-settleability. [ABSTRACT FROM AUTHOR]

Highlights: [•] In situ transesterification was successfully applied to wet microalgae. [•] Biodiesel was produced directly from wet microalgae in a single pot process. [•] The conversion yield reaches 91% using wet microalgae. [ABSTRACT FROM AUTHOR]