Search

Switching cultivation (mixotrophic-heterotrophic, 12 h:12 h) of Heynigia riparia SX01 was studied, the maximum biomass concentration of 3.55 g L −1 and lipid yield of 1.45 g L −1 were achieved after 8 days cultivation. The extracellular polymeric substance (EPS) was developed as co-product. Addition of MgSO 4 could enhance the production of EPS. The highest amount of 0.60 g L −1 EPS was obtained with the addition of 2 g L −1 MgSO 4 , the self-flocculation efficiency was as high as 83% at this condition. The total lipid and lipid fractions did not show differences with extra MgSO 4 . Based on the above results, a new biodiesel production model was proposed: culturing Heynigia riparia SX01 with extra 2 g L −1 MgSO 4 by switching cultivation and using self flocculation to collect microalgae for biodiesel production, while EPS was collected as valuable co-products. [ABSTRACT FROM AUTHOR]

To improve the biomass yield and lipid productivity, two desert microalgae, Desmodesmus sp. S81 and G41 were induced mutagenesis by Ethylmethane sulfonate (EMS), and obtained two potential mutants, Desmodesmus sp. S5 and G3 from the mutagenic clones for their greatly promoted biomass and lipid production. The results showed that the biomass yield, lipid content and lipid productivity of the mutant strains S5 and G3 were 778.10 mg·L −1 , 48.41% and 19.83 mg·L −1 ·d −1 , 739.52 mg·L −1 , 46.01%, and 17.92 mg·L −1 ·d −1 , respectively, which presented the increment of 45.50%, 8.00% and 74.24%, 20.67%, 10.35% and 55.77% than those of S81 and G41. Comparing with the wild strains, the mutants showed reduced PUFAs and glycol lipids, elevated MUFAs and neutral lipids contents, which were appropriate for biodiesel production. [ABSTRACT FROM AUTHOR]

The development of a culture system for Chlorella sp. GD to efficiently produce biomass and oil for biodiesel production was investigated. Chlorella sp. GD was cultivated with 0%, 25%, 50%, 75% and 100% piggery wastewater (diluted by medium) at 300 μmol m −2 s −1 , a 2% CO 2 aeration rate of 0.2 vvm and 26 ± 1 °C; after a 10-day culture in batch cultures, the maximum specific growth rate and biomass productivity of the microalga obtained in 100% piggery wastewater were 0.839 d −1 and 0.681 g L −1 d −1 , respectively. The highest lipid content and lipid productivity were 29.3% and 0.155 g L −1 d −1 at 25% wastewater, respectively. In semi-continuous cultures, the biomass and lipid productivities with 25–75% wastewater ratios were greater than 0.852 and 0.128 g L −1 d −1 , respectively. These results show that Chlorella sp. GD grows efficiently in piggery wastewater, and that a stable growth performance was achieved for long-term microalgal cultivation in a semi-continuous culture. [ABSTRACT FROM AUTHOR]

Highlights: [•] Marine diatom Chaetoceros muelleri grow well under high CO2 levels (10–20%). [•] The highest biomass, total and neutral lipid contents were all found under 10% CO2. [•] Total lipid content is 43.40% DW under 10% CO2 with highest biomass productivity. [•] Fatty acid composition of C. muelleri is very ideal for biofuels production. [•] C. muelleri have great potential to biodiesel produce using the flue gases. [Copyright &y& Elsevier]

Abstract: During the fermentation process, dissolved oxygen values and carbon-to-nitrogen ratios are critical factors influencing DHA productivity. This study employed an intermittent oxygen feeding method to maintain a 50% dissolved oxygen level and produced a dissolved oxygen fluctuation environment to facilitate both Aurantiochytrium limacinum SR21 growth and lipid accumulation. Study results indicated that at a 1.25 C:N ratio and medium composition of 100gL−1 glycerol, 40gL−1 yeast extract, and 40gL−1 peptone, A. limacinum SR21 achieved biomass at 61.76gL−1, lipid content at 65.2%, DHA concentration at 20.3gL−1, and DHA productivity at 122.62mgL−1 h−1, this result were better than most similar researches. Dissolved oxygen fluctuation environment also altered the fatty acid composition of A. limacinum SR21. In the late period of the fermentation process, C16:0 fatty acid ratios decreased significantly to below 5%, and C22:6 fatty acid ratios increased to 70%. [Copyright &y& Elsevier]

Abstract: A novel cultivation strategy called “sequential heterotrophy–dilution–photoinduction” was developed for efficient algal biomass and lipid production. Three Chlorella species were first cultivated heterotrophically to achieve high cell density, then the broth was diluted to suitable concentration (2–5g/L) and transferred to light environment for photoinduction. With this strategy, the Chlorella intracellular protein and chlorophyll increased rapidly to 50.87% and 32.97mg/g by a 12-h illumination, which were close to the level of cells cultivated photoautotrophically. Moreover, the lipid contents were increased by 84.57%, 70.65% and 121.59% within 24-h photoinduction for C. vulgaris, C. pyrenoidosa and C. ellipsoidea, respectively. Maximum lipid content as 26.11% of biomass and maximum lipid productivity of 89.89mg/L/d was both accomplished by C. pyrenoidosa. Further outdoor experiments showed consistent patterns. Therefore, the proposed strategy provided an effective approach for microalgal biomass production to meet the urgent need for both health food and biodiesel. [Copyright &y& Elsevier]

Abstract: Three different strains of colonial green alga Botryococcus bruanii Kutz. AP103, AP104 and AP105 were isolated from the freshwater lake Kolleru, Andhra Pradesh, India. The morphological features of these three isolates were studied under laboratory conditions. Molecular identification of the strains was carried out using 18S rRNA analysis and their systematic position was confirmed to species level as B. braunii. Among these isolates, B. braunii AP103 recorded highest biomass concentration of 1.7±0.12gL−1, 17% lipids, 17% proteins, 32% carbohydrates and 13% hydrocarbons under laboratory condition. Under open raceway pond AP103 produced a biomass concentration of 1.8±0.13gL−1, 19% lipids, 33% carbohydrates, 18% proteins and 11% hydrocarbons. The hydrocarbons profile showed the presence of heptadecane (34%) and hexadecane (12.5%). Oleic (25.7%), linolenic (34.26%) and palmitic (9.42%) acids were the major fatty acids present in the lipids extracted from AP103. [Copyright &y& Elsevier]

Abstract: Microalgae have the ability to grow rapidly, synthesize and accumulate large amounts (approximately 20–50% of dry weight) of lipids. A successful and economically viable algae based oil industry depends on the selection of appropriate algal strains. In this study ten species of microalgae were prospected to determine their suitability for oil production: Chaetoceros gracilis, Chaetoceros mulleri, Chlorella vulgaris, Dunaliella sp., Isochrysis sp., Nannochloropsis oculata, Tetraselmis sp., Tetraselmis chui, Tetraselmis tetrathele and Thalassiosira weissflogii. The study was carried out in 3L glass flasks subjected to constant aeration and controlled artificial illumination and temperature at two different salinities. After harvesting, the extraction of oil was carried out using the Bligh and Dyer method assisted by ultrasound. Results showed that C. gracilis presented the highest oil content and that C. vulgaris presented the highest oil production. [Copyright &y& Elsevier]

• Microwave treatment enhanced the biomass and lipid content of Scenedesmus sp. • Exopolysaccharides could be enhanced by microwave treatment. • Multiple products could be obtained from microwave treated microalgae. • Necessary fuel properties were not affected by microwave treatment. The present study focuses on the use of microwave irradiation to improve the production of lipid, exopolysaccharide and biomass in the microalgae Scenedesmus sp. Microwave treatment conditions such as microwave power, duty cycle % and time was optimized to increase the biomass and lipid content of Scenedesmus sp. Microwave power 100 W, duty cycle 40 %, and 2 min treatment time led to a substantial improvement in the biomass and lipid content. Due to the simultaneous improvement in both the biomass and lipid content, the total lipid production was improved from 0.76 (microwave untreated) to 1.42 g/L (microwave treated) (12 days grown cells). In addition, with biomass and lipid content, microwave treatment also enhanced the production of Exopolysaccharides (EPS) up to 2.3-folds. Furthermore, biodiesel properties were improved to some extent after the microwave treatment. Microwave irradiation is a promising physical treatment method for microalgae to improve total lipid production. [ABSTRACT FROM AUTHOR]

• Biomass pretreatment is an energy-intensive step in microalgal biorefineries. • Process selection must take into account integration in biorefineries. • Thermolysis is the most cost-efficient processes for further biodigestion. • Enzymatic hydrolysis, pulsed electric fields and autolysis are promising steps. Microalgae are sources of nutritional products and biofuels. However, their economical processing is challenging, because of (i) the inherently low concentration of biomass in algal cultures, below 0.5%, (ii) the high-water content in the harvested biomass, above 70%; and (iii) the variable intracellular content and composition. Cell wall structure and strength vary enormously among microalgae, from naked Dunaliella cells to robust Haematococcus cysts. High-value products justify using fast and energy-intensive processes, ranging from 0.23 kWh/kg dry biomass in high-pressure homogenization, to 6 kWh/kg dry biomass in sonication. However, in biofuels production, the energy input must be minimized, requiring slower, thermal or chemical pretreatments. Whichever the primary fraction of interest, the spent biomass can be processed into valuable by-products. This review discusses microalgal cell structure and composition, how it affects pretreatment, focusing on technologies tested for large scale or promising for industrial processes, and how these can be integrated into algal biorefineries. [ABSTRACT FROM AUTHOR]

• Three-phase portioning process (TPP) was used in lipid extraction from microalgae biomass. • Three-phase portioning process could extract lipid from high water content and non-broken microalgae biomass. • Various parameters were studied to improve TPP performance. • Ethyl acetate/DKP ratio, and temperature, incubation time were crucial for efficient extraction. • TPP was found to extract around 15.9% of total lipid transformable to methyl esters. In present study, lipids were extracted from unbroken microalga Chlorella vulgaris with high water content (50% microalgal solution) through three-phase partitioning (TPP). The method was found to extract around 15.9% of total lipid transformable to methyl esters (LTMEs) from unbroken microalgal cells which is two times of Bligh and Dyer method. We investigated the effects of various parameters on TPP performance and were optimised through response surface methodology. The results indicated that incubation duration, temperature and extraction time were positively correlated with LTME extraction efficiency. The optimum temperature was 60 °C, incubation duration was 120 min, extraction time was 60 min, ratio of solvent to DKP was 1:1. The FAME yield was calculated as 12.05% and major fatty acids together accounted for 71.33% which indicated the great potential of the proposed lipid extraction procedure for microalga-based biodiesel production. [ABSTRACT FROM AUTHOR]

• Algae were grown in walnut shell extracts (WSE) supplemented with carbon dioxide. • CO 2 significantly boosted the biomass and lipid productivities of algae under WSE cultivation. • A combined strategy was developed for WSE utilization and biofuel production. Microalgae are a promising biofuel resource, but their high cost and low productivity hinder their commercial applications. In the present study, Monoraphidium sp. QLZ-3 was cultivated in walnut shell extracts (WSE) supplemented with carbon dioxide (CO 2). Biomass was enhanced from 0.40 g L−1 to 1.18 g L−1, and lipid content reached 49.54% in WSE-12% CO 2 media. Biomass and lipid productivity reached 196.88 and 97.52 mg L−1 d−1, which were 1.33- and 1.57-fold higher than those of the control, respectively. The amount of carbohydrates increased, but the protein contents decreased. Furthermore, the application of CO 2 promoted nutrient and polyphenol absorption and upregulated the expression levels of lipid biosynthetic genes of this WSE-cultivated alga. These results indicated that coupling WSE and CO 2 could be an efficient strategy to enhance biofuel production by microalgae. [ABSTRACT FROM AUTHOR]