Haijian Yang

Sufficient utilization of natural fluctuating light intensity is an effective approach of promoting lipid productivity in oleaginous microalgal cultivation outdoors

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, 106.61mgL(-1)d(-1)) and lipid yields (35.06, 32.45mgL(-1)d(-1)) under HFI. The highest areal lipid productivities of 9.06 and 8.95gm(-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.

NaCl as an effective inducer for lipid accumulation in freshwater microalgae Desmodesmus abundans

In order to evaluate the efficiency and potential of salt addition-based two-stage cultivation technology, on the basis of urea as nitrogen source, we compared four types of salts (NaCl, NaHCO3, NaS2O3 and NaAc) as inducers for lipid production in Desmodesmus abundans. The maximum biomass productivity (270.08mgL(-1)d(-1)) was obtained by using 0.25gL(-1) urea. The highest lipid productivity (67.08mgL(-1)d(-1)) and better biodiesel quality were realized by addition of 20gL(-1) NaCl, and the optimal time point for salt addition was determined at 1.79gL(-1) of biomass density. Further cost analysis demonstrated this cultivation process was relatively economical. Above results suggest that NaCl addition is an economical and applicable strategy for lipid enhancement and can be extended for microalgae-based biodiesel production.

Rapid neutral lipid accumulation of the alkali-resistant oleaginous Monoraphidium dybowskii LB50 by NaCl induction

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 20gL(-1) NaCl. Total lipid and NL contents respectively increased to 41.7% and 17.48% in 1d. The highest NL productivity was also achieved at both the 5L (24.13mgL(-1)d(-1)) and 140L (13.05mgL(-1)d(-1), 3.43gm(-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.

Culture modes and financial evaluation of two oleaginous microalgae for biodiesel production in desert area with open raceway pond

Cultivation modes of autotrophic microalgae for biodiesel production utilizing open raceway pond were analyzed in this study. Five before screened good microalgae were tested their lipid productivity and biodiesel quality again in outdoor 1000L ORP. Then, Chlorella sp. L1 and Monoraphidium dybowskii Y2 were selected due to their stronger environmental adaptability, higher lipid productivity and better biodiesel properties. Further scale up cultivation for two species with batch and semi-continuous culture was conducted. In 40,000L ORP, higher lipid productivity (5.15 versus 4.06gm(-2)d(-1) for Chlorella sp. L1, 5.35 versus 3.00gm(-2)d(-1) for M. dybowskii Y2) was achieved in semi-continuous mode. Moreover, the financial costs of 14.18

Selection of microalgae for biodiesel production in a scalable outdoor photobioreactor in north China

gal(-1) and 13.31

Lipid accumulation by NaCl induction at different growth stages and concentrations in photoautotrophic two-step cultivation of Monoraphidium dybowskii LB50.

gal(-1) for crude biodiesel in two microalgae with semi-continuous mode were more economically feasible for commercial production on large scale outdoors.

Optimizing light regimes on growth and lipid accumulation in Ankistrodesmus fusiformis H1 for biodiesel production

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 Scenedesmusobtusus 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 20.2gm(-2)d(-1) and highest lipid content of 31.7% in a culture of 140L. S. obtusus XJ-15 was further identified as the best candidate for liquid biofuel production, characterized by average areal growth rate of 23.8gm(-2)d(-1) and stable lipid content of above 31.0% under a scale of 1400L over a season.

A new biofilm based microalgal cultivation approach on shifting sand surface for desert cyanobacterium Microcoleus vaginatus

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 5gL(-1) NaCl induction, as well as for protein under 10gL(-1) NaCl induction. At late-exponential growth phase (LEGP), the highest lipid productivity was obtained at 20gL(-1) NaCl. At stationary phase (SP) the highest lipid productivity was also under 20gL(-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.

Effects of temperature and its combination with high light intensity on lipid production of Monoraphidium dybowskii Y2 from semi-arid desert areas

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.

Physiological responses of freshwater oleaginous microalgae Desmodesmus sp. NMX451 under nitrogen deficiency and alkaline pH-induced lipid accumulation.

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<0.001). According to the maximal photosynthetic activity and microalgal productivity, cultivation time of microalgal biofilm on sand surface should be controlled around 15-25days, with water content at 10%. Based on the biofilm cultivation system, microalgal biomass yield reached up to 11gm-2 eventually on the sand surface.