摘要：Oleaginous microalgae are considered as promising sources of biofuels and biochemicals due to their high lipid content and other high-value components such as pigments, carbohydrate and protein. This study aimed to develop an efficient biorefinery process for utilizing all of the components in oleaginous microalgae. Acetone extraction was used to recover microalgal pigments prior to processes for the other products. Microalgal lipids were converted into biodiesel (fatty acid methyl ester, FAME) through a conventional two-step process of lipid extraction followed by transesterification, and alternatively a one-step direct transesterification. The comparable FAME yields from both methods indicate the effectiveness of direct transesterification. The operating parameters for direct transesterification were optimized through response surface methodology (RSM). The maximum FAME yield of 256 g/kg-biomass was achieved when using chloroform:methanol as co-solvents for extracting and reacing reagents at 1.35:1 volumetric ratio, 70 degrees C reaction temperature, and 120 min reaction time. The carbohydrate content in lipid-free microalgal biomass residues (LMBRs) was subsequently acid hydrolyzed into sugars under optimized conditions from RSM. The maximum sugar yield obtained was 44.8 g/kg-LMBRs and the protein residues were recovered after hydrolysis. This biorefinery process may contribute greatly to zero-waste industrialization of microalgae based biofuels and biochemicals.

摘要：Microalgae produce increased lipid content accompanied by a significant decrease in cell density with decreasing nitrate concentration. Magnetic fields (MF) have been reported as a factor that could accelerate metabolism and growth in microalgae culture. Thus, this study aimed to optimize the influence of MF and nitrate concentration (sodium nitrate, N) on the growth and lipid productivity of Nannochloropsis oculata. A single-factor experiment integrated with response surface methodology (RSM) via central composite design (CCD) was performed. The results showed that the maximum specific growth rate (0.24 d(-1)) and maximum lipid productivity (38 mg L-1 d(-1)) obtained in this study were higher than those of the control culture (by 166% and 103%, respectively). This study also found that the two-way interaction term MF x N had a significant effect on cell growth but not on lipid production. It was concluded that to design appropriate MF for enhanced lipid productivity due to cell growth, further research must focus on developing an understanding of the relationship between the bioeffects of the magnetic field and the proteomic changes involved in lipid accumulation strategies. This approach would enable the design of conditions to obtain inexpensive high-value products from N. oculata.

摘要：In recent years, widespread efforts have been directed towards decreasing the costs associated with microalgae culture systems for the production of biofuels. In this study, a simple and inexpensive strategy to bio-prospect and cultivate mixed indigenous chlorophytes with a high carbohydrate content for biomethane and biohydrogen production was developed. Mixed microalgae were collected from four different water-bodies in Queretaro, Mexico, and were grown in Bold's basal mineral medium and secondary effluent from a wastewater treatment plant using inexpensive photo-bioreactors. The results showed large fluctuations in microalgal genera diversity based on different culture media and nitrogen sources. In secondary effluent, Golenkinia sp. and Scenedesmus sp. proliferated. The carbohydrate content, for secondary effluent, varied between 12% and 57%, and the highest volumetric and areal productivity were 61 mg L-1 d(-1) and 4.6 g m(-2) d(-1), respectively. These results indicate that mixed microalgae are a good feedstock for biomethane and biohydrogen production. (c) 2014 Elsevier Ltd. All rights reserved.

摘要：The emissions of ammonia and CO2 from animal housing operations are a major challenge for concentrated animal feeding operations (CAFOs). A microalgae culture process was developed as a bio-scrubber to remove these gases. The green algae Scenedesmus dirnorphus was grown in a fiat panel photobioreactor aerated with ammonia- and CO2-laden aft, with ammonia mass loading being fixed at 42.4 ing/L.day and CO2 mass loading rates ranging from 0.64 to 5.49 g/L.clay. Within the range of the CO2 mass loading rate investigated, the ammonia gas removal rate was kept constant (41-42 mg/L.day) with a high removal efficiency (>95%) from the inlet gas. The majority (80-90%) of the ammonia was removed by algal cell assimilation, with a small portion (10-12%) being removed via liquid dissolution. The CO2 removal rate and removal efficiency, however, highly depended on the CO2 mass loading rate used. The highest CO2 removal rate (0.6 g/L.clay) was achieved at CO2 mass loading rate of 1.18 g/L.day, but the highest CO2 removal efficiency (78%) was achieved at the 0.64 g/L.clay CO2 mass loading rate. The cell biomass obtained contained 7-8% lipid, 55-60% protein, and 21-28% of carbohydrates. The amino acid profiles of the algal biomass are close to the ideal protein profiles for typical animal feeds, with a high ratio of essential amino acids. Collectively, the study shows that microalgae culture is an effective method for mitigation of ammonia and CO2 emissions from CAFOs, with the potential for use as an animal feed additive. (C) 2015 Elsevier By. All rights reserved.

摘要：Microbial contamination of growth reactors is a major concern for microalgal biofuel production. In this study, the oleaginous, CO2-tolerant microalga Scenedesmus dimorphus was combined with a wastewater-derived microbial community and grown in replicated sequencing batch photobioreactors. The reactors were sparged with either ambient air or 20% v/v CO2. In the initial growth cycles, air and the 20% CO2 reactors were similar in terms of growth and microbial community structure. Beyond the fourth growth cycle, however, the ambient air reactors had larger decreases in cell density and growth rate, and increases in species richness and non-algal microorganisms compared to the 20% CO2 reactors. Both qPCR and rDNA sequence analyses demonstrated a greater loss in S. dimorphus enrichment in the ambient-air reactors compared to the 20% CO2 reactors. These results demonstrate that environmental parameters can be used to delay the adverse impacts of microbial contamination in open, mixed-culture microalgae bioreactors. (C) 2015 Elsevier Ltd. All rights reserved.

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摘要：In response to the energy crisis, global warming and climate changes, microalgae have received increasingly global attention as a renewable, alternative and sustainable source for the production of biodiesel. Much original research regarding microalgal biodiesel production has been reported. However, microalgal biodiesel faces plenty of challenges that current cultivation and biodiesel conversion is economically unfeasible for industrial applications on a large scale. This perspective paper first briefly discusses the latest advances in liquid transportation biodiesel production from microalgal biomass, including microalgal growth, biomass harvesting and drying, lipid extraction and biodiesel conversion. Subsequently, strategies for the future development of microalgal biodiesel have been proposed and discussed, in an attempt to reduce the cost gap. From the microalgal biodiesel production chain perspective, genetic and metabolic engineering, isolation of suitable species, high-efficiency bioreactor development, efficient culturing system development, optimal harvest process design, high-efficiency lipid extraction and transesterification method development will have critical roles to play. It is worthy of note that the increase of the outcome credits can also realize the reduction of the economic gap, and the main measures include appropriate glycerol recovery and reutilization, integration with wastewater treatment and CO2 mitigation together with microalgal biorefinery for the production of multiple co-products with high values. Finally, concluding remarks are put forward.

摘要：Microalgae have great biotechnological potential but the high cost of traditional formulae culture media is one of the limiting factors to their commercial cultivation. As an alternative, the use of residual water from other activities has been proposed as a culture medium. The goal of this study was to produce Chaetoceros muelleri, Nannochloropsis oculata and Tetraselmis chuii biomass using residual water from an intensive Litopenaeus vannamei biofloc cultivation system and to verify the ammoniacal nitrogen, nitrite, nitrate and orthophosphate consumption. The microalgae cultures were developed until the second day of their stationary phase in the following treatments: 100% f/2 culture media; 100% residual water; residual water diluted 50% with marine water. T. chuii and N. oculata presented the best relative biomass average (576 mg L (1); 474 mg L (1)) (P > 0.05). All the species completely assimilated the orthophosphate in 2 days. In 10 days, T. chuii and N. oculata assimilated 87% and 85% of nitrate respectively. It can be concluded that residual water from an L. vannamei biofloc cultivation system can be used as an alternative culture medium for T. chuii and N. oculata biomass production. Moreover, the microalgae biomass proved to be very effective in recycling the dissolved nutritive salts.

摘要：Holding cells in the cultivation broth for subsequent medium replacement is often considered as one of the most difficult procedures during perfusion cell culture. Although a number of harvest approaches have been reported in the past decades, their drawbacks such as high cost, increased contamination, and/or labor consuming remain obstacles for practical application. To overcome these challenges, a novel resonant ultrasound field-incorporated dynamic photobioreactor system (RUF-DPBS) was developed in which the cell retention and medium replacement are carried out by acoustic radiation forces and gravity, respectively. Based on the collection efficiency of microalgae, the RUF operation was optimized by 1 MHz and output intensity of 8 W/cm(2) with circulating velocity of 2 mL/min whereby 93% of Nannochloropsis oculata in 30 mL can be collected within 2-h operation. Moreover, the cells cultured with RUF-DPBS in which the medium was changed every three days exhibited increased volumetric productivity that the yields of biomass, total lipid, and eicosapentaenoic acid of the N. oculata after 12-days cultivation significantly enhanced 2.6, 2.1, and 2.5 folds (P < 0.05 for each), respectively, as compared to the group without medium replacement. In summary, the semiautomatic RUF-DPBS offers a non-fouling, labor-efficient, and cost-effective means for high-density microalgae culture in continuous mode. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

摘要：Switchable solvents with hydrophobicities that can be reversibly changed were evaluated as single solvents for oil extraction from wet biomass. Three switchable solvents, N,N-dimethylcyclohexylamine (DMCHA), N-ethylbutylamine (EBA), and dipropylamine, were used to extract oil from the undisrupted wet paste of harvested Chlorella sp. microalgae. The oil extraction yields for the three solvents were 13.6%, 12.3%, and 7.0%, respectively. However, single hydrophobicity solvents n-hexane and [Bmim][PF6] were unable to extract any oil, achieving yields of 0% and 0.7%, respectively. A parametric study was performed to evaluate the effects of temperature, cell disruption duration, and extraction duration on the effectiveness of oil extraction. The results were used to develop a statistical model to predict oil extraction effectiveness under different conditions. The switchable solvents were also evaluated in simultaneous extraction-reaction systems used to convert the oils extracted from wet microalgae into biodiesel. The use of enzymes was found to enhance the production yield of biodiesel by 33%. The highest biodiesel yield of 47.5% was achieved using DMCHA at 35 degrees C with a methanol/oil molar ratio of 6:1 and a 30% enzyme loading employing a solvent program comprising 1-h cell disruption, 1-h extraction/reaction, and 1-h phase separation steps. The proposed strategy of using a single solvent for simultaneous extraction and reaction could substantially simplify biodiesel production from wet microalgae.