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1.
Algae biofuel has the potential to replace fossil fuels. However, cultivation and productivity of target algae need improvement, while controlling undesired organisms that can lower the efficiency of production systems. A central composite design and response surface model were utilized to predict cultivation optima of marine microalga, Nannochloropsis salina, under a suite of environmental parameters. The effects of salinity, pH, and temperature and their interactions were studied on maximum sustainable yield (MSY, a measure for biomass productivity), lipid content of N. salina, and invading organisms. Five different levels of each environmental predictor variable were tested. The environmental factors were kept within ranges that had previously been determined to allow positive N. salina growth (14.5–45.5 PSU; pH 6.3–9.7; 11–29 °C). The models created for this experiment showed that N. salina’s MSY and lipid content are not strongly affected over the broad range of salinity and temperature values. Calculated optima levels were 28 PSU/20 °C for MSY and 14.5 PSU/20 °C for lipid accumulation, but neither value significantly influenced the model. However, pH was the most important factor to influence algae productivity, and pH optimum was estimated around 8. Both MSY and lipid content were strongly reduced when pH deviated from the optimum. Occurrence of invading organisms seemed stochastic, and none of the environmental factors studied significantly influenced abundance. In conclusion, pH should be kept around 8 for maximum productivity of N. salina. Temperature and salinity should be kept around 20 °C and 28 PSU; however, moderate variations are not too much of a concern and might enhance lipid content of N. salina.  相似文献   

2.
Oils, carbohydrates, and fats generated by microalgae are being refined in an effort to produce biofuels. The research presented here examines two marine microalgae, Nannochloropsis salina (green alga) and Phaeodactylum tricornutum (diatom), when grown with 0 (no addition), 0.5, 1.0, 2.0, and 5.0 g L?1 NaHCO3 added to an f/2 medium during the growth phase (GP) and a nutrient induced (nitrate limitation) lipid formation phase (LP). We hypothesize that the addition of NaHCO3 is a sustainable and practical strategy to increase cellular density and concentrations of lipids in microalgae as well as the rate of lipid accumulation. In N. salina, final cell densities were significantly (p?<?0.05) higher in the NaHCO3-treated cells than the control while in P. tricornutum the cell densities were higher with >[NaHCO3] during the GP. During the LP, cell densities were generally higher in the NaHCO3-treated cells compared with controls. F V/F M (efficiency of photosystem II) patterns paralleled those for cell density with generally higher values with higher concentrations of NaHCO3 and significantly different values between controls and 5.0 g L?1 NaHCO3 at the end of the GP (p?<?0.05). F V/F M was variable between treatments in P. tricornutum (0.3–0.65) but less so in N. salina for (0.5–0.7) regardless of [NaHCO3]. The lipid index (measured with Nile red), used as a proxy for triacylglycerides (TAGs), was 10.2?±?6.5 and 4.4?±?2.9 (fluorescence units/OD cells ×1000) for N. salina and P. tricornutum, respectively, at the end of the GP. At the end of the LP, the lipid index was eight and four times higher than during the GP in the corresponding 5.0 g L?1 NaHCO3 treatments, revealing that N. salina was accumulating more lipid than P. tricornutum. Dry weights essentially doubled during LP compared with GP for N. salina; this was not the case for P. tricornutum. In general, the percentage of ash in dry weights was significantly higher in the LP relative to the corresponding GP treatments for P. tricornutum; this was not the case for N. salina. During the LP, there was also less soluble protein in N. salina compared to GP; differences were not significant in cells growing with 2.0 or 5.0 g L?1 NaHCO3. In P. tricornutum, faster growing cells had more soluble protein during the GP and LP; differences between treatments were significant. P. tricornutum generally accumulated significantly more crude protein than N. salina at higher [NaHCO3]; there was three times more crude protein in the highest NaHCO3 (5.0 g L?1) treatment compared with the controls. C:N ratios (mol:mol) were similar across treatments during GP: 7.03?±?0.12 and 10.16?±?0.41 for N. salina and P. tricornutum, respectively. Further, C:N ratios increased with increasing [NaHCO3] during LP. Species-specific fatty acid methyl ester (FAMEs) profiles were observed. While C16:0 was lower in P. tricornutum compared to N. salina, the diatom produced more C16:1 and C14 but not C18:3. Monounsaturated fatty acids (MUFA) significantly increased in N. salina in the LP compared to GP and in response to increasing [NaHCO3] (t tests; p?<?0.05). Saturated fatty acids (SFA) responded similarly but to a lesser degree. There were more polyunsaturated fatty acids (PUFA) in N. salina than MUFAs or SFAs. In P. tricornutum, there were generally more SFAs, MUFAs and PUFAs in P. tricornutum during LP than GP in the corresponding NaHCO3 treatments. These findings reveal the importance of considering NaHCO3 as a supplemental carbon source in the culturing marine phytoplankton in large-scale production for biofuels.  相似文献   

3.
The halotolerant cyanobacterium Anabaena sp was grown under NaCl concentration of 0, 170 and 515 mM and physiological and proteomic analysis was performed. At 515 mM NaCl the cyanobacterium showed reduced photosynthetic activities and significant increase in soluble sugar content, proline and SOD activity. On the other hand Anabaena sp grown at 170 mM NaCl showed optimal growth, photosynthetic activities and comparatively low soluble sugar content, proline accumulation and SOD activity. The intracellular Na+ content of the cells increased both at 170 and 515 mM NaCl. In contrast, the K+ content of the cyanobacterium Anabaena sp remained stable in response to growth at identical concentration of NaCl. While cells grown at 170 mM NaCl showed highest intracellular K+/Na+ ratio, salinity level of 515 mM NaCl resulted in reduced ratio of K+/Na+. Proteomic analysis revealed 50 salt-responsive proteins in the cyanobacterium Anabaena sp under salt treatment compared with control. Ten protein spots were subjected to MALDI-TOF–MS/MS analysis and the identified proteins are involved in photosynthesis, protein folding, cell organization and energy metabolism. Differential expression of proteins related to photosynthesis, energy metabolism was observed in Anabaena sp grown at 170 mM NaCl. At 170 mM NaCl increased expression of photosynthesis related proteins and effective osmotic adjustment through increased antioxidant enzymes and modulation of intracellular ions contributed to better salinity tolerance and optimal growth. On the contrary, increased intracellular Na+ content coupled with down regulation of photosynthetic and energy related proteins resulted in reduced growth at 515 mM NaCl. Therefore reduced growth at 515 mM NaCl could be due to accumulation of Na+ ions and requirement to maintain higher organic osmolytes and antioxidants which is energy intensive. The results thus show that the basis of salt tolerance is different when the halotolerant cyanobacterium Anabaena sp is grown under low and high salinity levels.  相似文献   

4.
Natural saline lakes in Western Australia were sampled for microalgae species and strains with potential for large-scale outdoor cultivation over a wide range of salinities for biofuels production. Using a rational isolation and screening process, several Tetraselmis strains (Chlorophyta, Chlorodendrales) with a broad range of salinity tolerance were identified and were characterised further for their potential for biofuels production. Specific growth rates increased from 0.8 to 1.2 days?1 when the medium salinity was decreased from 11 to 3 % (w/v) NaCl (1.88 to 0.51 M NaCl) in batch cultivation mode, thereby indicating quick adaptation to large salinity changes. In general, ash-free dry weight (AFDW), total lipid, protein and carbohydrate contents per cell were highest in the early stages of growth. Salinity increases led to an increase in cell AFDW, with the highest mean maximum of 2555?±?659 pg AFDW.cell?1 at 11 % (w/v) NaCl in the strains Tetraselmis MUR 167 and MUR 219 which had been in culture for many years, as compared to the mean maximum of 981?±?141 pg AFDW.cell?1 the in newly isolated strains MUR 230, 231, 232 and 233. Similar observations on total lipid, protein and carbohydrate content per cell were made between the two groups of strains. Overall, all strains yielded high biomass and total lipid productivities over a very wide range of salinities without large variation in their gross biochemical composition and growth pattern. Based on AFDW and total lipid productivity data, the order of preference for selecting strains for further investigation for large-scale culture was MUR 231?>?MUR 233?>?MUR 219?>?MUR 230?>?MUR 232?>?MUR 167. The Tetraselmis spp. were also very competitive as shown by the outdoor cultivation of diatom, Halamphora coffeaeformis MUR 158, in parallel with Tetraselmis sp. MUR 167 which resulted in the diatom being outcompeted by the green alga. Our results demonstrate the high commercial potential of euryhaline Tetraselmis spp. for cultivation over a broad range of salinity in outdoor cultures.  相似文献   

5.
The Antarctic Lake Wujka (62°09′28.3″S, 58°27′56.3″W), a shallow water body (Z m  = 1.38 m), situated at c.15 m from the seashore was sampled at two points (Sp 1 and Sp 2) at 3-day intervals from December 2003 to June 2004. The two sampling points differing in location and depth: Sp 1 (Z m  = 0.50 m) was the shallowest site, located near the lake outlet, while Sp 2 (Z m  = 1.38 m) was the deepest spot of the lake. The population density of Notholca squamula salina peaked in June (at 114 ind. l?1) at Sp 1, while at Sp 2 peaked in January (80 ind. l?1) and May (150 ind. l?1). Spearman non-parametric correlations with temperature, salinity, total dissolved solids, conductivity and pH revealed effects that characterize N. squamula salina as a species capable of surviving in a range of aquatic environments, but with a preference for high salinity, food and low temperature. It occurred in highest numbers when the diatom Achnanthes lanceolata var. rostrata (Øestrup) Hust., normally a benthic species, was stirred up into the water during storms that also raised the lake’s salinity to above 20 psu.  相似文献   

6.
Heat shock proteins (HSPs) are ubiquitous protective proteins that play crucial roles in plant development and adaptation to stress, and the aim of this study is to characterize the HSP gene in alfalfa. Here we isolated a small heat shock protein gene (MsHSP17.7) from alfalfa by homology-based cloning. MsHSP17.7 contains a 477-bp open reading frame and encodes a protein of 17.70-kDa. The amino acid sequence shares high identity with MtHSP (93.98 %), PsHSP17.1 (83.13 %), GmHSP17.9 (74.10 %) and SlHSP17.6 (79.25 %). Phylogenetic analysis revealed that MsHSP17.7 belongs to the group of cytosolic class II small heat shock proteins (sHSP), and likely localizes to the cytoplasm. Quantitative RT-PCR indicated that MsHSP17.7 was induced by heat shock, high salinity, peroxide and drought stress. Prokaryotic expression indicated that the salt and peroxide tolerance of Escherichia coli was remarkably enhanced. Transgenic Arabidopsis plants overexpressing MsHSP17.7 exhibited increased root length of transgenic Arabidopsis lines under salt stress compared to the wild-type line. The malondialdehyde (MDA) levels in the transgenic lines were significantly lower than in wild-type, although proline levels were similar between transgenic and wild-type lines. MsHSP17.7 was induced by heat shock, high salinity, oxidative stress and drought stress. Overexpression analysis suggests that MsHSP17.7 might play a key role in response to high salinity stress.  相似文献   

7.
The accumulation of triacylglycerols (TAG) is a common feature among actinobacteria belonging to Rhodococcus genus. Some rhodococcal species are able to produce significant amounts of those lipids from different single substrates, such as glucose, gluconate or hexadecane. In this study we analyzed the ability of different species to produce lipids from olive oil mill wastes (OMW), and the possibility to enhance lipid production by genetic engineering. OMW base medium prepared from alperujo, which exhibited high values of chemical oxygen demand (127,000 mg/l) and C/N ratio (508), supported good growth and TAG production by some rhodococci. R. opacus, R. wratislaviensis and R. jostii were more efficient at producing cell biomass (2.2–2.7 g/l) and lipids (77–83% of CDW, 1.8–2.2 g/l) from OMW than R. fascians, R. erythropolis and R. equi (1.1–1.6 g/l of cell biomass and 7.1–14.0% of CDW, 0.1–0.2 g/l of lipids). Overexpression of a gene coding for a fatty acid importer in R. jostii RHA1 promoted an increase of 2.2 fold of cellular biomass value with a concomitant increase in lipids production during cultivation of cells in OMW. This study demonstrates that the bioconversion of OMW to microbial lipids is feasible using more robust rhodococal strains. The efficiency of this bioconversion can be significantly enhanced by engineering strategies.  相似文献   

8.
Volatile fatty acids (VFAs) that can be derived from food wastes were used for microbial lipid production by Chlorella protothecoides in heterotrophic cultures. The usage of VFAs as carbon sources for lipid accumulation was investigated in batch cultures. Culture medium, culture temperature, and nitrogen sources were explored for lipid production in the heterotrophic cultivation. The concentration and the ratio of VFAs exhibited significant influence on cell growth and lipid accumulation. The highest lipid yield coefficient and lipid content of C. protothecoides grown on VFAs were 0.187 g/g and 48.7 %, respectively. The lipid content and fatty acids produced using VFAs as carbon sources were similar to those seen on growth and production using glucose. The techno-economic analysis indicates that the biodiesel derived from the lipids produced by heterotrophic C. protothecoides with VFAs as carbon sources is very promising and competitive with other biofuels and fossil fuels.  相似文献   

9.
A simple reliable method with fast response for lipid detection and quantification is proposed, combining a new highly lipophilic fluorescent probe BODIPY BD-C12 and image analysis to determine the algal lipid content and the lipid production in the microalgae Nannochloropsis sp. Lipid bodies stained with BODIPY BD-C12 have a characteristic multicolor fluorescence, and their volumes were determined using a sphere volume approach. The method developed was applied in the evaluation of lipid accumulation by Nannochloropsis sp. under different cultivation conditions (varying nitrate and salinity concentrations and combined effect of these two variables). The results show an increase of lipid content in Nannochloropsis sp. cultivated in nitrogen replete and depleted conditions, from 9.4 to 40.8 μm3 cell?1 and 35.5 to 73.5%, respectively. The findings are also compared with conventional methods for determination of neutral lipids and with results obtained from the dyes Nile Red and BODIPY 505/515. A reasonable agreement between neutral lipid production measured by BODIPY BD-C12 and gravimetric methods (correlation coefficient of 0.98) was obtained. The neutral lipids production decreased from 964.6 to 244.8 mg L?1 and from 809.1 to 396.7 mg L?1, as the nitrate concentration increased from 0 to 0.3 g L?1. It is observed that, with the two commercially available dyes, lipid quantification using Nile Red leads to an overestimation of lipids, while the use of BODIPY 505/515 promoted unreliable measures due to rapid bleaching of the chromophore. The method proposed shows excellent potential to become a standard, yet advanced, strategy for rapid evaluation and quantification of intracellular lipids in microalgae, a crucial step of the scaling-up process involved in the production of biobased products.  相似文献   

10.
Members of the plant glycine-rich RNA-binding proteins (GR-RBPs) family have been reported in flowering, development, circadian rhythms, biotic and abiotic stresses. Particularly, GR-RBPs are reported to function as RNA chaperones, promoting growth and acclimation during cold shock. It is indispensable to further question the efficacy and mechanism of GR-RBPs under various environmental strains. Monitoring the expression of stress-regulated proteins under stress conditions has been a beneficial strategy to study their functional roles. In an effort to elucidate the NtGR-RBP1 function, stress markers such as salinity, drought, low temperature and heat stresses were studied. The NtGR-RBP1 gene was expressed in E. coli followed by the exposure to stress conditions. Recombinant E. coli expressing NtGR-RBP1 were more tolerant to stresses, e.g., salinity, drought, cold and heat shock. Recombinants exhibited higher growth rates compared to control in spot assays. The tolerance was further confirmed by monitoring the growth in liquid culture assays. Cells expressing NtGR-RBP1 under salt (500 mM NaCl), drought (20% PEG), cold (4 and 20 °C) and heat stresses (50 °C) had enhanced growing ability and better endurance. Our study supports the notion that the protective role of NtGR-RBP1 may contribute to growth and survival during diverse environmental stresses.  相似文献   

11.
The yeast strain XJ5-1 isolated from the Taklimakan desert soil was identified to be a strain of Aureobasdium melanogenum and could produce a large amount of melanin when it was grown in the PDA medium, but its melanin biosynthesis and expression of the PKS gene responsible for the melanin biosynthesis was significantly repressed in the presence of (NH4)2SO4. However, A. melanogenum P5 strain isolated from a mangrove ecosystem grown in both the presence and the absence of (NH4)2SO4 did not produce any melanin. The cell size of A. melanogenum XJ5-1 strain was much higher than that of A. melanogenum P5 strain. The melanized cells of the yeast strain XJ5-1 had higher tolerance to UV radiation, oxidation (200.0 mM H2O2), heat treatment (40 °C), salt shock (200.0 g/L NaCl), desiccation and strong acid hydrolysis (6.0 M HCl) at high temperature (80 °C) than the non-melanized cells of the same yeast strain XJ5-1. At the same time, the melanized cells of the yeast strain XJ5-1 also had higher tolerance to UV radiation, oxidation (200.0 mM H2O2), desiccation and strong acid hydrolysis (6.0 M HCl) at high temperature (80 °C) than A. melanogenum P5 strain, but had similar resistance to heat treatment (40 °C) and salt shock (200.0 g/L NaCl) compared to those of A. melanogenum P5 strain. All the results revealed that many characteristics of A. melanogenum XJ5-1 isolated from the Taklimakan desert soil was different from those of A. melanogenum P5 strain isolated from the mangrove ecosystem.  相似文献   

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E. coli JM109?envC?nlpD deleted with genes envC and nlpD responsible for degrading peptidoglycan (PG) led to long filamentous cell shapes. When cell fission ring location genes minC and minD of Escherichia coli were deleted, E. coli JM109?minCD changed the cell growth pattern from binary division to multiple fissions. Bacterial morphology can be further engineered by overexpressing sulA gene resulting in inhibition on FtsZ, thus generating very long cellular filaments. By overexpressing sulA in E. coli JM109?envC?nlpD and E. coli JM109?minCD harboring poly(3-hydroxybutyrate) (PHB) synthesis operon phbCAB encoded in plasmid pBHR68, respectively, both engineered cells became long filaments and accumulated more PHB compared with the wild-type. Under same shake flask growth conditions, E. coli JM109?minCD (pBHR68) overexpressing sulA grown in multiple fission pattern accumulated approximately 70 % PHB in 9 g/L cell dry mass (CDM), which was significantly higher than E. coli JM109?envC?nlpD and the wild type, that produced 7.6 g/L and 8 g/L CDM containing 64 % and 51 % PHB, respectively. Results demonstrated that a combination of the new division pattern with elongated shape of E. coli improved PHB production. This provided a new vision on the enhanced production of inclusion bodies.  相似文献   

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We attempted to enhance the growth and total lipid production of three microalgal species, Isochrysis galbana LB987, Nannochloropsis oculata CCAP849/1, and Dunaliella salina, which are capable of accumulating high content of lipid in cells. Low nitrogen concentration under photoautotrophic conditions stimulated total lipid production, but a decreasing total lipid content and an increasing biomass were observed with increasing nitrogen concentration. Among the different carbon sources tested for heterotrophic cultivation, glucose improved the growth of all three strains. The optimal glucose concentration for growth of I. galbana LB987 and N. oculata CCAP849/1 was 0.02 M, and that of D. salina was 0.05 M. Enhanced growth occurred when they were cultivated under heterotrophic or mixotrophic conditions compared with photoautotrophic conditions. Meanwhile, high total lipid accumulation in cells occurred when they were cultivated under photoautotrophic or mixotrophic conditions. During mixotrophic cultivation, biomass production was not affected significantly by light intensity; however, both chlorophyll concentration and total lipid content increased dramatically with increasing light intensity up to 150 µmol/m2/s. The amount and composition ratio of saturated and unsaturated fatty acids in cells were different from each other depending on both species and light intensity. The highest accumulation of total fatty acid (C16–C18) among the three strains was found from cells of N. oculata CCAP849/1, which indicates that this species can be used as a source for production of biodiesel.  相似文献   

16.
The content of lysophosphatidylethanolamine (LPE) in Y. pseudotuberculosis cells was found to increase during their growth at 8 °C under stationary conditions (without stirring the medium) and at 37°C when the medium contained glucose. The maximum level of LPE (up to 45% of the total phospholipids) was observed in cells grown at 8°C under stationary conditions. Such cells showed decreas growth rate, a reduced yield of biomass, an altered cell morphology, and an increased cell area. The cells contained unsaturated fatty acids, phosphatidylethanolamine (PE), and total phospholipids in small amounts, whereas neutral lipids and diphosphatidylglycerol were abundant. In addition, the cells contained an amount of methylated PE and phospholipids of unknown structure. Irrespective of whether the temperature for growth was low or high, the LPE-rich cells showed a high value (32–36°C) of the maximum temperature of thermal transition of lipids (T max). This finding is indicative of a densification of the membrane lipid matrix of the LPE-rich cells. The suggestion is made that LPE is accumulated in bacterial cells in response to stress caused by oxygen deficiency and pH decrease in the course of glucose fermentatin. The possible relationship between LPE accumulation and the virulence of Y. pseudotuberculosis cells grown at low temperatures is discussed.  相似文献   

17.
Aechmea ramosa Mart. ex Schult. f. is an endemic bromeliad of the Brazilian Atlantic Forest. The current habitat degradation of this hotspot biome threatens this species, which besides having an important ecological role, is also of invaluable ornamental interest. Plant tissue culture has been used in mass propagation and conservation of various bromeliads. We have established a micropropagation protocol for A. ramosa var. ramosa using leaf explants grown in MS medium supplemented with 2 μM of 1-naphthaleneacetic acid (NAA) and 2 μM of 6-benzylaminopurine (BAP) that showed higher values of shoot induction. NAA and BAP are associated with the production of proteins involved in stress response modulation, metabolic activity, and cell division, the latter being involved in inducing the differentiation of competent cells. After 120 d of culture, each explant presented 28.9 shoots with an average size of 27.8 mm, with no variation in either Stomatal Index or density of the regenerated shoots. Plantlets measuring above 15-mm height were successfully acclimatized, presenting 100% survival rate. Thus, this protocol can be used for mass propagation of A. ramosa, and to supply demand for the market of ornamental plants. Furthermore, it represents an important tool for the conservation of this species and maintenance of an in vitro germplasm.  相似文献   

18.
A Gram staining negative, rod-shaped, aerobic bacterial strain J5-3T with a single polar flagellum was isolated from coking wastewater collected from Shaoguan, Guangdong, China. It was motile and capable of optimal growth at pH 6–8, 30 °C, and 0–2 % (w/v) NaCl. Its predominant fatty acids were 11-methyl C18:1 ω7c (29.2 %), C16:0 (20.6 %), C19:0 cyclo ω8c (18.2 %), C18:0 (11.0 %), and C18:1 ω7c/C18:1 ω6c (10.9 %) when grown on trypticase soy agar. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two unknown glycolipids (GL1, GL2), and two unknown phospholipid (PL1, PL2). The predominant ubiquinone was Q-10, and the genome DNA G+C content was 61.7 mol %. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain J5-3T belonged to the family Hyphomicrobiaceae in Alphaproteobacteria. It shared the 16S rRNA gene sequence similarities of 93.8–96.1 % with the genus Devosia, 94.5–94.8 % with the genus Pelagibacterium, and <92.0 % with all the other type strains in family Hyphomicrobiaceae. It can be distinguished from the closest phylogenetic neighbors based on several phenotypic and genotypic features, including α-galactosidase activity, tetracycline susceptibility, major fatty acid composition, polar lipid profile, DNA gyrase B subunit (gyrB) gene sequence, and random-amplified polymorphic DNA profile. Therefore, we consider strain J5-3T to represent a novel species of a novel genus within the family Hyphomicrobiaceae, for which the name Paradevosia shaoguanensis gen. nov., sp. nov. is proposed. The type strain of Paradevosia shaoguanensis is J5-3T (=CGMCC 1.12430T =LMG 27409T).  相似文献   

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