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Temperature and light intensity are important environmental factors influencing microalgae for biodiesel production. The aim of present work was to study the effects of temperature (15 °C, 25 °C, and 35 °C) and its combination with high light intensity (HL, 400 μmol photon m−2 s−1) on lipid production of Monoraphidium dybowskii Y2 which was isolated from desert. The results demonstrated that algal growth was only inhibited at 15 °C. Promoted lipid content and decreased Fv/Fm were observed in 15 °C and 35 °C. Cellular carbohydrate, protein conversion and membrane lipid (MGDG, DGDG and SQDG) remodeling contributes for lipid accumulation. Stress combined temperatures with HL are benefit for lipid production, especially desired neutral lipid productivity all exceed 40 mg L−1 d−1. Fatty acids compositions of C16:0 and C18:1 were further promoted under 15 °C or 35 °C combined with HL. Thus, M. dybowskii Y2 will well-adapted to outdoors cultivation for biodiesel production.

Chlorella sp. and Monoraphidium sp. were the potential microalgal species for lipid production. This study aimed to investigate different light intensities (40, 200, 400 lmol photon m(-2) s(-1)) on physiological changes, photosynthetic carbon partitioning and neutral lipid accumulation in both microalgae. Results suggested that under high light (HL, 400 lmol photon m (2) s (1)), chlorophyll degraded, protein and carbohydrate content decreased; more carbon allocated into lipid as well as most of intracellular space was occupied by lipid bodies. Moreover, with the lipid accumulation, Fv/Fm decreased and ROS scavenging enzyme increased. Membrane lipid reduced dramatic (29.73-37.97%) to format NL (71.66% of total lipid in Chlorella sp. L1 and 60.65% in Monoraphidium dybowskii Y2). The NL productivity under HL (51.36 and 49.71 mg L (1) d (1)) were more than 3 times of those under LL. Additionally, FAME profiles proved that the useful fatty acid components for biodiesel production were enhanced under HL. (C) 2015 Elsevier Ltd. All rights reserved.

NaCl induction in photoautotrophic two-step cultivation is very promising, but time node and concentration are critical to the entire production. In this study Monoraphidium dybowskii LB50 was subjected to different NaCl concentrations at different growth phases. Results showed that during the initial phase (IP), fixed carbon was used for sugar and lipid under 5 g L-1 NaCl induction, as well as for protein under 10 g L-1 NaCl induction. At late-exponential growth phase (LEGP), the highest lipid productivity was obtained at 20 g L-1 NaCl. At stationary phase (SP) the highest lipid productivity was also under 20 g L-1 NaCl but lower than that of LEGP. In summary, lipid content and quality were improved at all growth phases under NaCl induction. Therefore, cultivation scale can be sued to determine the time node and dosage of the inducer, thereby realizing the economic efficiency of the fundamental guarantee in photoautotrophic two-step cultivation. (C) 2015 Elsevier Ltd. All rights reserved.

Biofilm based microalgal cultivation has recently received great attention because of its low water requirement and harvesting cost. However, the contradiction between microalgal attachment and harvesting still hinders the development of this technology. Therefore, in this study the most readily available and inexpensive shifting sand was used as attached substrate for microalgal (Microcoleus vaginatus) biofilm cultivation under different water conditions. After the inoculation, a stable and easily peeled microalgal biofilm formed through filamentous binding and exopolysaccharide cementing. In general, microalgal biomass, photosynthetic activity and exopolysaccharide accumulation were all significantly affected by the cultivation time, water content and their interaction (P

The aim of this study was to optimize the light regimes including initial inoculum density, photoperiod and light intensity on the growth and lipid (TAG) accumulation in Ankistrodesmus fusiformis H1 for biodiesel production. At last, the strategy of 4.47 mM urea with initial OD680-0.5, 18:6h light/dark cycle and 200 μmol photon m(-2) s(-1) regimes were optimized. The lipid productivity of 116.88 mg L(-1)d(-1) and 57.58% neutral lipid in total lipid were achieved finally. Moreover, the changes of photosynthetic activity, pigments contents and biochemical compositions revealed that more carbon flow to lipid synthesis. Therefore, A. fusiformis H1 is an ideal candidate for biodiesel production by utilizing light appropriately.

The effects of fluctuating intensity of solar radiation on biomass and lipid in oleaginous microalgae are important. However, this topic has not been the subject of studies for a long time. In this study, four oleaginous microalgae from semi-arid areas were screened and cultivated outdoors under different fluctuating intensities. Results showed that the highest lipid productivities and neutral lipid (NL) contents occurred under high fluctuating intensity (HFI), in which 13-20% of the increased NL came from glycolipid transformation without phospholipid conversion. Chlorella sp. L1 and Monoraphidium dybowskii Y2 obtained from biological soil crusts in desert had the largest biomass (137.13, 106.61 mg L-1 d(-1)) and lipid yields (35.06, 32.45 mg L-1 d(-1)) under HFI. The highest areal lipid productivities of 9.06 and 8.95 g m(-2) d(-1) and better biodiesel quality were observed under HFI. Accordingly, sufficiently adopting fluctuating light intensity outdoors to culture microalgae was an economic and effective approach. (C) 2014 Elsevier Ltd. All rights reserved.

The aim of this study was to identify the most promising species as biodiesel feedstock for large-scale cultivation in north China. Eight species of microalgae, selected on the basis of indoor screening, were tested for lipid productivity and the suitability of their fatty acid profiles for biodiesel production under outdoor conditions. Among them, three species Desmodesmus sp. NMX451, Desmodesmus sp. T28-1 and Scenedesmus obtusus XJ-15 were selected for further characterization due to their possessing higher lipid productivities and favorable biodiesel properties. The best strain was S. obtusus XJ-15, with highest biomass productivity of 20.2 g m(-2) d(-1) and highest lipid content of 31.7% in a culture of 140 L. S. obtusus XJ-15 was further identified as the best candidate for liquid biofuel production, characterized by average areal growth rate of 23.8 g m(-2) d(-1) and stable lipid content of above 31.0% under a scale of 1400 L over a season. (C) 2014 Elsevier Ltd. All rights reserved.

NaCl is an effective inducer of lipid accumulation in freshwater microalgae, but little is known on whether the enhanced lipid components are desired. To address this issue, Monoraphidium dybowskii LB50 from a freshwater habitat was selected, cultivated, and subjected to NaCl induction at different scales outdoors. Results showed that the optimal salt concentration reduced glycolipid (GL) content, as well as enhanced neutral lipid (NL) and phospholipid (PL) contents. Moreover, GL was preferentially converted to NL at 20 g L-1 NaCl. Total lipid and NL contents respectively increased to 41.7% and 17.48% in 1 d. The highest NL productivity was also achieved at both the 5 L (24.13 mg L-1 d(-1)) and 140 L (13.05 mg L-1 d-1, 3.43 g m(-2) d(-1)) scales. These results suggest that NL accumulated effectively and rapidly at different scales, indicating that this strategy has broad application prospects for the scale-up cultivation of oily algae. (C) 2014 Elsevier Ltd. All rights reserved.