High biomass production and CO<Subscript>2</Subscript> fixation from biogas by <Emphasis Type="Italic">Chlorella</Emphasis> and <Emphasis Type="Italic">Scenedesmus</Emphasis> microalgae using tequila vinasses as culture medium

Tequila vinasses (TVs) generated during Tequila production are brown liquid residues rich in nutrients. The nutrient content of agro-industrial effluents represents an excellent resource to support low-cost biomass production of microalgae; nonetheless, it is crucial to select the suitable microalgal strain to attain the highest biomass production in each residue used. In this study, biomass production, CO₂ fixation from biogas, and cell compound accumulation by Chlorella vulgaris U162, Chlorella sp., Scenedesmus obliquus U169, and Scenedesmus sp. using biodigested and filtered TVs as culture medium were evaluated and compared with the conventional microalgal culture media, C30, BG-11, Bold 3N, and Bristol. The four microalgae evaluated attained the highest biomass production and CO₂ fixation rate cultured in both residues, accumulating mainly carbohydrates and proteins although the most appropriate microalga to be cultured in TVs was Chlorella sp., recording 2.30 g L^?1. Moreover, the nutrient ratio of filtered TVs was ideal to support biomass production while biodigested TVs need to be supplemented with nitrogen. Overall, these results demonstrated that tequila vinasses are an excellent resource to support high and quick biomass production of microalgae, which can be used to obtain biofuels as ethanol, biogas, and supplement food depicting an extra benefit during the appropriate disposal of this residue.     

Bioremediation of wastewater from edible oil refinery factory using oleaginous microalga Desmodesmus sp. S1

Edible oil industry produced massive wastewater, which requires extensive treatment to remove pungent smell, high phosphate, carbon oxygen demand (COD), and metal ions prior to discharge. Traditional anaerobic and aerobic digestion could mainly reduce COD of the wastewater from oil refinery factories (WEORF). In this study, a robust oleaginous microalga Desmodesmus sp. S1 was adapted to grow in WEORF. The biomass and lipid content of Desmodesmus sp. S1 cultivated in the WEORF supplemented with sodium nitrate were 5.62 g·L^?1 and 14.49%, whereas those in the WEORF without adding nitrate were 2.98 g·L^?1 and 21.95%. More than 82% of the COD and 53% of total phosphorous were removed by Desmodesmus sp. S1. In addition, metal ions, including ferric, aluminum, manganese and zinc were also diminished significantly in the WEORF after microalgal growth, and pungent smell vanished as well. In comparison with the cells grown in BG-11 medium, the cilia-like bulges and wrinkles on the cell surface of Desmodesmus sp. S1 grown in WEORF became out of order, and more polyunsaturated fatty acids were detected due to stress derived from the wastewater. The study suggests that growing microalgae in WEORF can be applied for the dual roles of nutrient removal and biofuel feedstock production.     

The effect of gradual increase in salinity on the biomass productivity and biochemical composition of several marine,halotolerant<Emphasis Type="Bold">,</Emphasis> and halophilic microalgae

Open ponds are the preferred cultivation system for large-scale microalgal biomass production. To be more sustainable, commercial scale biomass production should rely on seawater, as freshwater is a limiting resource, especially in places with high irradiance. If seawater is used for both pond fill and evaporative volume makeup, salinity of the growth media will rise over time. It is not possible for any species to achieve optimum growth over the whole saline spectrum (from seawater salinity level up to salt saturation state). In this study, we investigated the effects of gradual salinity increase (between 35 and 233 ppt) on biomass productivity and biochemical composition (lipid and carbohydrate) of six marine, two halotolerant, and a halophilic microalgae. A gradual and slow stepped salinity increase was found to expand the salinity tolerance range of tested species. A gradual reduction in biomass productivity and maximum photochemical efficiency was observed as a consequence of increased salinity in all tested species. Among the marine microalgae, Tetraselmis showed highest biomass productivity (32 mg L^?1 day^?1) with widest salinity tolerance range (35 to 109 ppt). Halotolerant Amphora and Navicula were able to grow from 35 ppt to 129 ppt salinity. Halophilic Dunaliella was the only species capable of growing between 35 and 233 ppt and showed highest lipid content (56.2%) among all tested species. This study showed that it should be possible to maintain high biomass in open outdoor cultivation utilizing seawater by growing Tetraselmis, Amphora, and Dunaliella one after another as salinity increases in the cultivation system.     

Characterization of cell structural change,growth, lipid accumulation,and pigment profile of a novel oleaginous microalga, <Emphasis Type="Italic">Vischeria stellata</Emphasis> (Eustigmatophyceae), cultured with different initial nitrate supplies

The appropriate microalgal species and the optimal nitrogen supply in culture medium are vital factors in maximizing biomass and metabolite productivities in microalgae. Vischeria stellata is an edaphic unicellular eustigmatophycean microalga. Cytological and ultrastructural characteristics and the effects of different initial nitrate-nitrogen concentrations on growth, lipid accumulation, fatty acid profile, and pigment composition were investigated in the present study. The cell structures of V. stellata changed with the degree of nutrient utilization and growth phase. The initial nitrate concentration for the optimal growth of V. stellata ranged from 6.0 to 9.0 mM. The maximum total lipid (TLs), neutral lipid (NLs), and total fatty acid (TFAs) contents were 55.9, 51.9, and 44.7 % of dry biomass, respectively. The highest volumetric productivity of TLs, NLs, and TFAs reached 0.28, 0.25, and 0.21 g L^?1 day^?1, respectively. V. stellata had a suitable fatty acid profile for biodiesel production, as well as containing eicosapentaenoic acid (EPA) for nutraceutical applications. In addition, the content β-carotene, increased gradually as culture time was prolonged, resulting in its exclusive production at the end of cultivation. V. stellata is a promising microalgal strain for the production of biofuels and bioproducts.     

Enrichment as a screening method for a high-growth-rate microalgal strain under continuous cultivation system

Microalgae are a promising feedstock for renewable biodiesel production. High productivity of biodiesel production from microalgae is directly related to growth rate as well as lipid content of cells. In the present study, an enrichment process in a continuous cultivation system was developed to screen a high-growth-rate microalga from a mixed culture of microalgal species; Chlorella vulgaris, Chlorella protothecoides, and Chlamydomonas reinhardtii were used as test organisms for our experiments. The time-dependent washout of mixed microalgal pool was executed to successfully enrich the C. reinhardtii, which exhibits the higher growth rate than C. vulgaris and C. protothecoides under turbidostat conditions within 75 h. The domination of C. reinhardtii in the mixed culture was validated by on-line monitoring of growth rate and flowcytometric analysis. For the time-efficient production of microalgal biomass, this screening process has a high potential to segregate the fast-growing microalgal strains from the pool of various uncharacterized microalgal species and random mutants.     

核桃壳提取液用于单针藻Monoraphidium sp.QLZ-3培养产油脂

[目的] 研究核桃壳提取液（walnut shell extracts,WSE）对单针藻Monoraphidium sp.QLZ-3生长和油脂积累的影响。[方法] 向BG-11培养基中添加不同量的WSE（培养基中保留有BG-11中全部营养成分）。[结果] 结果显示,当BG-11培养基中的WSE含量为40%时,单针藻的生物量产率及油脂产率达到（534.70±4.07）mg/（L·d）和（296.35±15.36）mg/（L·d）,相比对照组分别提高了的14.82%和33.50%,蛋白质和碳水化合物含量分别有不同程度的上调和下调。与对照组相比,微藻中谷胱甘肽（glutathione,GSH）和超氧化物歧化酶（superoxide dismutase,SOD）含量与活性均上调。此外,WSE作用下,微藻对多酚的移除达到84.37%,同时上调了核酮糖1,5-二磷酸羧化酶基因（ribulose 1,5-bisphosphate carboxylase/oxygenase,rbcL）和乙酰辅酶A羧化酶（acetyl coenzyme A carboxylase,accD）基因的表达量。[结论] 研究表明,WSE联合BG-11可以提高微藻的生物量产率和油脂产率,降低微藻培养的原料成本,为核桃壳的资源化利用及微藻的工业化生产提供了一定的技术支撑。     

Utilization of Organic Liquid Fertilizer in Microalgae Cultivation for Biodiesel Production

The utilization of organic liquid fertilizer PAL-1 as the culture medium of the microalga Chlorella vulgaris was investigated for the purpose of biodiesel production. Cell growth and lipid accumulation in PAL-1 were evaluated and compared with those in the artificial medium BG-11. Cells showed mixotrophic growth when utilizing the organic liquid fertilizer PAL-1. The rates of cell growth (0.143 d^-1) and N consumption (14.9 mg/L/d) in PAL-1 were almost the same as those in BG-11, under the presence of 2% CO₂-enriched aeration and light irradiation. Lipid synthesis was triggered in PAL-1 on day 4, when nitrogen was completely consumed, and the lipid content reached up to 48% thereafter. Lipid productivity could be enhanced using repeated-batch cultivation in which cells were exposed to N limitation repeatedly, and thus lipid synthesis was induced while maintaining a sufficiently high cell density.     

Stress-induced changes in pigment and fatty acid content in the microalga Desmodesmus sp. Isolated from a White Sea hydroid

Effects of light intensity, nitrogen availability, and inoculum density on growth and the content of esterified fatty acids (FA), chlorophylls, and carotenoids in Desmodesmus sp. 3Dp86E-1 chlorophyte alga isolated from the White Sea hydroid Dynamena pumila L. were investigated. The growth of algae in the complete BG-11 medium was not limited by irradiances up to 480 μE/(m² s) PAR but depended on the inoculum density. Under nitrogen starvation conditions, high-intensity light retarded growth of the microalga; this effect was less pronounced in the cultures initiated at high inoculum densities. The highest FA percentage in biomass (30% at the 3rd day of cultivation) was detected in nitrogen-starving cultures grown under high light conditions; however, the highest volumetric FA content (0.25 g/L) was attained on a complete medium at 480 μE/(m² s). An increase in the content of oleic acid (18:1) on the background of a decrease in linolenic acid (18:3) was characteristic of the microalga under stress conditions. The microalga was found to be non-carotenogenic. Nitrogen starvation brought about a dramatic decrease in chlorophyll content on the background of relatively constant carotenoid content. On nitrogen-deplete medium, the high light did not trigger the adaptive response of the pigment apparatus. The changes in absorption spectra of Desmodesmus sp. 3Dp86E-1 cell suspensions reflected the increase in relative contribution of carotenoids to light absorption by the microalgal cells; these changes were tightly related with FA accumulation. The mechanisms of acclimation of Desmodesmus sp. 3Dp86E-1 to high light and nitrogen starvation are discussed in view of possible biotechnological applications of this alga.     

Microalgal industry in China: challenges and prospects

Over the past 15 years, China has become the major producer of microalgal biomass in the world. Spirulina (Arthrospira) is the largest microalgal product by tonnage and value, followed by Chlorella, Dunaliella, and Haematococcus, the four main microalgae grown commercially. China’s production is estimated at about two-thirds of global microalgae biomass of which roughly 90 % is sold for human consumption as human nutritional products (‘nutraceuticals’), with smaller markets in animal feeds mainly for marine aquaculture. Research is also ongoing in China, as in the rest of the world, for other high-value as well as commodity microalgal products, from pharmaceuticals to biofuels and CO₂ capture and utilization. This paper briefly reviews the main challenges and potential solutions for expanding commercial microalgae production in China and the markets for microalgae products. The Chinese Microalgae Industry Alliance (CMIA), a network founded by Chinese microalgae researchers and commercial enterprises, supports this industry by promoting improved safety and quality standards, and advancement of technologies that can innovate and increase the markets for microalgal products. Microalgae are a growing source of human nutritional products and could become a future source of sustainable commodities, from foods and feeds, to, possibly, fuels and fertilizers.     

Potential Anti-proliferative and Immunomodulatory Effects of Marine Microalgal Exopolysaccharide on Various Human Cancer Cells and Lymphocytes In Vitro

Marine microalgal exopolysaccharides (EPSs) have drawn great attention due to their biotechnological potentials such as anti-viral, anti-oxidant, anti-lipidemic, anti-proliferative, and immunomodulatory activities, etc. In the present study, the EPS derived from microalgae Thraustochytriidae sp.-derived mutant GA was investigated for its anti-proliferation and immunomodulation. Anti-cancer efficacy of the microalgal EPS was examined for the alterations in cell proliferation and cell cycle-related gene expression that occur in three types of human cancer cell lines, BG-1 ovarian, MCF-7 breast, and SW-620 colon cancer cell lines, by its treatment. Alterations in immunoreactivity by the microalgal EPS were examined by measuring its influence on the growth of T and B lymphocytes and cytokine production of T cells. In cell viability assay, the microalgal EPS inhibited cancer cell growth at the lowest concentration of 10^?11 dilution and in a dose-responsive manner within the range of dilution of 10^?11~10^?3. In addition, the protein expression of cell cycle progression genes such as cyclin D1 and E in these cancer cell lines was significantly reduced by the microalgal EPS in a dose- and a time-dependant manner. In cell proliferation assay using T and B cells, the microalgal EPS induced B cell proliferation even at the lowest dilution of 10^?11, but not T cells. In cytokine assay, the microalgal EPS decreased the formation of IL-6 and INF-γ at 10^?3 dilution compared to the control and had no significant effects on TNF-α. Collectively, these findings suggest that the EPS derived from microalgae Thraustochytriidae sp. GA has an anti-proliferative activity against cancer cells and an immunomodulatory effect by having an influence on B cell proliferation and cytokine secretion of T cells.     

Role of media composition in biomass and astaxanthin production of Haematococcus pluvialis under two-stage cultivation

In the present study, the effects of four different culture media on the growth, astaxanthin production and morphology of Haematococcus pluvialis LUGU were studied under two-step cultivation. The interactions between astaxanthin synthesis and secondary messengers, reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPK) were also investigated. In the first green vegetative cell stage, maximal biomass productivity (86.54 mg L⁻¹ day⁻¹) was obtained in BBM medium. In the induction stage, the highest astaxanthin content (21.5 mg g⁻¹) occurred in BG-11 medium, which was higher than in any other media. The expressions of MAPK and astaxanthin biosynthetic genes in BG-11 were higher than in any other media, whereas the ROS content was lower. Biochemical and physiological analyses suggested that the ROS, MAPK and astaxanthin biosynthetic gene expression was involved in astaxanthin biosynthesis in H. pluvialis under different culture media conditions. This study proposes a two-step cultivation strategy to efficiently produce astaxanthin using microalgae.

     

布朗葡萄藻的培养基选择及其产物代谢规律

通过对布朗葡萄藻分别在Chu13、Chu13×2和BG-11培养基中培养结果的比较,发现在气升式光照生物反应器中Chu13培养基最有利于布朗葡萄藻的生长和烃的合成,培养15d后,其生物量和粗烃质量分数分别为1.82g/L和58.7%;棕榈酸、油酸和亚麻酸是布朗葡萄藻的主要脂肪酸组成,Chu13培养获得的藻体不饱和脂肪酸比例最高。Chu13培养基中布朗葡萄藻代谢规律的研究表明:粗烃含量随着生物量的增加而逐渐增大,15d后粗烃产量达到最大值1.07g/L,不同生长周期烃的组成保持一致,布朗葡萄藻的烃主要由C33H56和C34H58组成;在布朗葡萄藻生长周期中,不饱和脂肪酸的比例显著上升,培养15d达到64%以上。     

Productivity and biochemical composition of <Emphasis Type="Italic">Tetradesmus obliquus</Emphasis> and <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis>: effects of different cultivation approaches

The present work evaluated biomass productivity, carbon dioxide fixation rate, and biochemical composition of two microalgal species, Phaeodactylum tricornutum (Bacillariophyta) and Tetradesmus obliquus (Chlorophyta), cultivated indoors in high-technology photobioreactors (HT-PBR) and outdoors both in pilot ponds and low-technology photobioreactors in a greenhouse in southern Italy. Microalgae were grown in standard media, under nitrogen starvation, and in two liquid digestates obtained from anaerobic digestion of agro-zootechnical and vegetable biomass. P. tricornutum, cultivated in semi-continuous mode in indoor HT-PBRs with standard medium, showed a biomass productivity of 21.0?±?2.3 g m^?2 d^?1. Applying nitrogen starvation, the lipid productivity increased from 2.3 up to 4.5?±?0.5 g m^?2 d^?1, with a 24 % decrease of biomass productivity. For T. obliquus, a biomass productivity of 9.1?±?0.9 g m^?2 d^?1 in indoor HT-PBR was obtained using standard medium. Applying liquid digestates as fertilizers in open ponds, T. obliquus gave a biomass productivity (10.8?±?2.0 g m^?2 d^?1) not statistically different from complete medium such as P. tricornutum (6.5?±?2.2 g m^?2 d^?1). The biochemical data showed that the fatty acid composition of the microalgal biomass was affected by the different cultivation conditions for both microalgae. In conclusion, it was found that the microalgal productivity in standard medium was about doubled in HT-PBR compared to open ponds for P. tricornutum and was about 20 % higher for T. obliquus.     

Effects of outdoor cultures on the growth and lipid production of <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis> using closed photobioreactors

One of the principal challenges for large scale production of microalgae is the high costs of biomass production. Aiming for minimize this problem, microalgal biodiesel production should focus on outdoors cultures, using available solar light and allowing lower energy cost process. Testing species that proved to be common and easy to culture may be a good approach in this process. The present work reports indoor-outdoor cultures of Phaeodactylum tricornutum using different bioreactors types, using cell growth, biochemical composition, and the profiles of the fatty acids produced as the parameters to test the optimization processes. The results show that the use of outdoor cultures is a good choice to obtain P. tricornutum biomass with a good potential for biodiesel production. The microalgae produced reached better growth efficiency, major lipid content and showed an increment in the percentage of saturated fatty acids (required on the biodiesel production) respect indoor cultures. These results are important to show the relevance of using outdoor cultures as a way to improve the efficiency and the energetic balance of the biodiesel production with P. tricornutum algae.     

<Emphasis Type="Italic">Tetraselmis suecica</Emphasis> culture for CO<Subscript>2</Subscript> bioremediation of untreated flue gas from a coal-fired power station

The accumulation of atmospheric CO₂, primarily due to combustion of fossil fuels, has been implicated in potential global climate change. The high rate of CO₂ bioremediation by microalgae has emerged as a favourable method for reducing coal-fired power plant emissions. However, coal-fired power station flue gas contains other chemicals such as SO_x which can inhibit microalgal growth. In the current study, the effect of untreated flue gas as a source of inorganic carbon on the growth of Tetraselmis in a 1000 L industrial-scale split-cylinder internal-loop airlift photobioreactor was examined. The culture medium was recycled after each harvest. Tetraselmis suecica grew very well in this airlift photobioreactor during the 7-month experiment using recycled medium from an electroflocculation harvesting unit. Increased medium SO₄ ^2? concentration as high as 870 mg SO₄ ^2??L^?1 due to flue gas addition and media recycling had no negative effect on the overall growth and productivity of this alga. The potential organic biomass productivity and carbon sequestration using an industrial-scale airlift PBR at International Power Hazelwood, Gippsland, Victoria, Australia, are 178.9?±?30 mg L^?1 day^?1 and 89.15?±?20 mg?‘C’?L^?1 day^?1, respectively. This study clearly indicates the potential of growing Tetraselmis on untreated flue gas and using recycled medium for the purpose of biofuel and CO₂ bioremediation.     

Contaminated bacterial effects and qPCR application to monitor a specific bacterium in <Emphasis Type="Italic">Chlorella</Emphasis> sp. KR-1 culture

To investigate the effects of bacteria contaminated in microalgal cultivation, several bacteria were isolated from four photobioreactors for Chlorella sp. KR-1 culture. A total of twenty-one bacterial strains isolated from the reactors and identified by 16S rRNA gene sequencing. Six bacteria, which were found from more than two reactors of the four photobioreactors, were introduced into co-culturing experiments with Chlorella sp. KR-1. Then, the bacterial influences on the productivity of microalgal biomass and lipids were assessed in the photoautotrophic- and mixotrophic microalgal cultivation by comparing them with axenic culture of Chlorella sp. KR-1. The results showed that both biomass and lipid production were significantly enhanced under mixotrophic conditions compared to photoautotropic conditions. However, an excess ratio (more than 10%) of bacterial cells to microalgal cells at the initial stage of mixotrophic cultivation has limited the growth of Chlorella sp. KR-1 because of the relatively fast growth of bacteria, especially under mixotrophic conditions. Moreover, it was proven that the strong biofilm formability of Sphingomonas sp. MB6 is the responsible strain to cause the biomass aggregation observed during the early stage of co-culture. The high abundance of Sphingomonas sp. MB6 during early cultivation period shown by qPCR results was also well corresponded with the period shown a strong biofilm formation, which suggested the applicability of qPCR to monitor a specific bacterial group in a microalgal culture.     

城市生活废水用于产油微藻培养

将废水与产油微藻培养结合起来,可以实现废水的无害化处理,还可为微藻的培养提供营养组分和大量水源。利用高产油栅藻,以城市生活废水为水源,在气泡柱式光反应器中,考察了添加不同营养组分对栅藻细胞的生长、生物质产量、总脂含量以及氮磷的去除情况的影响。结果表明：生活废水非常适合于产油微藻的培养,利用生活废水进行微藻培养中,仅需补充添加无机氮、无机磷、柠檬酸铁铵以及微量元素。但这些营养组分的加入量对藻细胞的生长、生物量和油脂积累有重要影响。在优化的废水培养基中微藻细胞浓度可达8.0 g/L左右,远高于标准BG11培养基5.0 g/L的水平。微藻细胞对于无机氮与磷有着高的吸收能力,在废水中加入185.25 mg/L以下无机氮,16.1 mg/L以下无机磷的条件下培养3~4 d后,培养液水体中未检测到有氮磷残留。由此表明利用城市生活废水培养含油微藻可以在获得微藻油脂产品的同时实现水体的无害化处理。     

Oil production by six microalgae: impact of flocculants and drying on oil recovery from the biomass

Oil production in batch photoautotrophic cultures of the following microalgae is reported: the freshwater microalgae Chlorella vulgaris, Choricystis minor, and Neochloris sp.; the marine microalgae Nannochloropsis salina and Cylindrotheca fusiformis; and C. vulgaris grown in a full-strength seawater medium. In all cases, the solvent extraction of lipids from freeze-dried biomass is compared with extraction from the fresh biomass paste. For all algae, the oils could be extracted equally effectively from freeze-dried samples and the paste samples (67–88 % moisture by weight). Moisture content determinations of the biomass using the freeze-drying method and the high-temperature oven drying were found to be equivalent for all algae. The biomass recovered by flocculation with metal salts (aluminum sulfate, ferric chloride) followed by centrifugation had a certain amount of the flocculant irreversibly bound to it. Washing failed to remove the adsorbed flocculants. For all algae, the adsorbed flocculants did not interfere with oil recovery by solvent extraction. The solvent system of chloroform–methanol–water proved highly effective for quantitative extraction of the lipids from all algae.     

Production characteristics of <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis> Bohlin grown on medium with artificial sea water

The growth of marine diatoms Phaeodactylum tricornutum was investigated on a medium with artificial sea water under artificial and natural light. The maximum specific growth rate was 0.7 day^–1, the productivity was 0.8 g/L day, and the maximum biomass was 3.86 g/L under artificial light in laboratory conditions. In the conditions of Crimea, the maximum productivity of P. tricornutum amounted to 6 g/m² day under natural light in an outdoor photobioreactor (pool). The results of cultivation of P. tricornutum in a pool with artificial seawater under natural light may serve as a basis for developing technologies for the industrial cultivation of algae.     

Biological fixation of nitrogen and growth of bacteria of the genus <Emphasis Type="Italic">Azotobacter</Emphasis> in liquid media in the presence of perfluorocarbons

The addition of perfluorocarbons (perfluorodecalin, carbogal, and perfluoromethyldecalin) to nitrogen-free liquid media during the submerged cultivation of bacteria of the genus Azotobacter was followed by (1) increases in biomass accumulation and nitrogenase activity and (2) fixation of molecular nitrogen. Addition of perfluorodecalin (5 vol %) to the culture medium of A. chroococcum ACB 121 contributed to increases in biomass accumulation, cell concentration (of more than by five times), nitrogenase activity (of 3.4 times), and total nitrogen content in the medium (of 4.5 times).