Demao Li

Preparation and characteristics of bio-oil from the marine brown alga Sargassum patens C. Agardh

The marine brown alga, Sargassum patens C. Agardh, floating on the Yellow Sea, was collected and converted to bio-oil through hydrothermal liquefaction with a modified reactor. A maximum yield of 32.1±0.2 wt.% bio-oil was obtained after 15 min at 340 °C, at a feedstock concentration of 15 g biomass/150 ml water, without using a catalyst. The bio-oil had a heating value of 27.1MJ/kg and contained water, lipid, alcohol, phenol, esters, ethers and aromatic compounds. The solid residue obtained had a high ash and oxygen content. The results suggest that S. patens C. Agardh has potential as biomass feedstock for fuel and chemical products.

Pyrolytic characteristics and kinetics of two brown algae and sodium alginate

The pyrolytic and kinetic characteristics of two macro-algae (Laminaria japonica and Sargassum pallidum) and sodium alginate were evaluated and compared at heating rates of 10, 30 and 50 degrees C min(-1) under an inert atmosphere after which the kinetic factors were calculated. The results indicated that three stages appeared during pyrolysis, moisture evaporation, primary devolatilization and residual decomposition. Significant differences in the average activation energy, thermal stability, final residuals and reaction rates existed between the samples studied. The primary devolatilization stage of L. japonica and S. pallidum could be described by the Avramic-Erofeev equation (n=3), whereas that of alginate sodium could be described by the Jander equation (n=2). Calculation of the most probable mechanism function of zone capital I, Ukrainian of the two macro-algae indicated that alginate was mainly decomposed during zone capital I, Ukrainian. The average activation energies of L. japonica, S. pallidum and sodium alginate were 207.7, 202.9 and 188.1 kJmol(-1), respectively.

Saccharina genomes provide novel insight into kelp biology.

Seaweeds are essential for marine ecosystems and have immense economic value. Here we present a comprehensive analysis of the draft genome of Saccharina japonica, one of the most economically important seaweeds. The 537-Mb assembled genomic sequence covered 98.5% of the estimated genome, and 18,733 protein-coding genes are predicted and annotated. Gene families related to cell wall synthesis, halogen concentration, development and defence systems were expanded. Functional diversification of the mannuronan C-5-epimerase and haloperoxidase gene families provides insight into the evolutionary adaptation of polysaccharide biosynthesis and iodine antioxidation. Additional sequencing of seven cultivars and nine wild individuals reveal that the genetic diversity within wild populations is greater than among cultivars. All of the cultivars are descendants of a wild S. japonica accession showing limited admixture with S. longissima. This study represents an important advance toward improving yields and economic traits in Saccharina and provides an invaluable resource for plant genome studies.

Microwave-assisted direct liquefaction of Ulva prolifera for bio-oil production by acid catalysis.

Production of bio-oil by microwave-assisted direct liquefaction (MADL) of Ulva prolifera was investigated, and the bio-oil was analyzed by elementary analysis, Fourier transform infrared spectroscopic analysis (FT-IR), and gas chromatography-mass spectrometry (GC-MS). The results indicate that the liquefaction yield is influenced by the microwave power, liquefaction temperature, liquefaction time, catalyst content, solvent-to-feedstock ratio and moisture content. The maximum liquefaction yield of U. prolifera (moisture content of 8%) was 84.81%, which was obtained under microwave power of 600 W for 30 min at 180 °C with solvent-to-feedstock ratio of 16:1 and 6% H(2)SO(4). The bio-oil was composed of benzenecarboxylic acid, diethyl phthalate, long-chain fatty acids (C(13) to C(18)), fatty acid methyl esters and water. The results suggest that U. prolifera is a viable eco-friendly, green feedstock substitute for biofuels and chemicals production.

Using ammonia for algae harvesting and as nutrient in subsequent cultures

Microalgae have been considered as a promising feedstock for biofuels and greenhouse gas reduction. A low-cost harvesting technology without secondary contamination for down-stream extraction is a key requirement to make algal biofuel commercially viable. A novel harvesting method using ammonia as a flocculant to make the algal biomass settable was devised and studied. Another major advantage of this approach is that the ammonia added will be reused as fertilizer in the subsequent cultures. The results indicated that ammonia-induced flocculation led to more than 99% removal of algae at 12h. The OD(600) of algae growing in the ammonia-enriched flocculation medium treated with heating and CO(2) was 2 times than that of initial after 6 days. These results suggested that this flocculation method was efficient, convenient and allowed the reuse of the flocculated medium, therefore providing an option for economic harvesting and cultivation of microalgae.

Process optimization for microwave-assisted direct liquefaction of Sargassum polycystum C.Agardh using response surface methodology

Response surface methodology (RSM) was used to optimize the microwave-assisted direct liquefaction of Sargassum polycystum C.Agardh in ethylene glycol (EG) with H(2)SO(4) as a catalyst. Based on the results of single factor experiments, EG-to-feedstock ratio, temperature and catalyst content were chosen as independent variables for a central composite rotatable design (CCRD). The optimal liquefaction conditions were estimated as: the EG-to-feedstock ratio of 18.50:1 (w/w), the temperature of 170°C, the reaction time of 15 min, catalyst content of 9.6% (catalyst/EG, w/w%) and microwave power of 400 W with the liquefaction yield of 87.70%. The bio-oils were mainly composed of fatty acid methyl ester and alkane with a long chain from C(17) to C(20).

Comparative studies of the pyrolytic and kinetic characteristics of maize straw and the seaweed Ulva pertusa.

Seaweed has attracted considerable attention as a potential biofuel feedstock. The pyrolytic and kinetic characteristics of maize straw and the seaweed Ulva pertusa were studied and compared using heating rates of 10, 30 and 50°C min−1 under an inert atmosphere. The activation energy, and pre-exponential factors were calculated by the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Popescu methods. The kinetic mechanism was deduced by the Popescu method. The results indicate that there are three stages to the pyrolysis; dehydration, primary devolatilization and residual decomposition. There were significant differences in average activation energy, thermal stability, final residuals and reaction rates between the two materials. The primary devolatilization stage of U. pertusa can be described by the Avramic-Erofeev equation (n = 3), whereas that of maize straw can be described by the Mampel Power Law (n = 2). The average activation energy of maize straw and U. pertusa were 153.0 and 148.7 KJ mol−1, respectively. The pyrolysis process of U.pertusa would be easier than maize straw. And co-firing of the two biomass may be require less external heat input and improve process stability. There were minor kinetic compensation effects between the pre-exponential factors and the activation energy.

Detection and quantitation of lipid in the microalga Tetraselmis subcordiformis (Wille) Butcher with BODIPY 505/515 staining.

BODIPY 505/515, a lipophilic bright green fluorescent dye was tested for lipid detection in the microalga Tetraselmis subcordiformis. A concentration of 0.28 μg ml(-1) and staining for 6 min was optimal. Lipid bodies stained with BODIPY505/515 had a characteristic green fluorescence. Their volumes were determined using the sphere volume formula. Lipid accumulation under different nitrogen concentrations was analyzed. With an increase in NaNO(3) concentration from 0 to 240 mg L(-1), the maximum algal concentration increased from 8.23 ± 0.62 (× 10(5) cells ml(-1)) to 1.61 ± 0.13 (×10(6) cells ml(-1)), while the maximum volume of intracellular neutral lipid decreased from 9.78 ± 1.77 μm(3) cell(-1) to 6.00 ± 0.59 μm(3) cell(-1). A comparison of the lipid contents measured by BODIPY 505/515 staining and the gravimetric method showed a positive correlation coefficient of R(2) = 0.93. BODIPY 505/515 staining is a promising method in lipid quantitation in T. subcordiformis.

Allelopathic Interactions between the Opportunistic Species Ulva prolifera and the Native Macroalga Gracilaria lichvoides

Allelopathy, one type of direct plant competition, can be a potent mechanism through which plant communities are structured. The aim of this study was to determine whether allelopathic interactions occur between the opportunistic green tide-forming species Ulva prolifera and the native macroalga Gracilaria lichvoides, both of which were collected from the coastline of East China sea. In laboratory experiments, the presence of G. lichvoides at 1.25 g wet weight L−1 significantly inhibited growth and photosynthesis of U. prolifera at concentrations of 1.25, 2.50, and 3.75 g wet weight L−1 (p<0.05) in both semi-continuous co-culture assays and in co-culture assays without nutrient supplementation. In contrast, although U. prolifera had a density effect on G. lichvoides, the differences among treatments were not significant (p>0.05). Culture medium experiments further confirmed that some allelochemicals may be released by both of the tested macroalgae, and these could account for the observed physiological inhibition of growth and photosynthesis. Moreover, the native macroalgae G. lichvoides was a stronger competitor than the opportunistic species U. prolifera. Collectively, the results of the present study represent a significant advance in exploring ecological questions about the effects of green tide blooms on the macroalgal community.

Enhanced hydrolysis of Macrocystis pyrifera by integrated hydroxyl radicals and hot water pretreatment.

Integrated hydroxyl radicals and hot water pretreatment (IHRHW) was employed in the bioconversion of the brown macroalgae Macrocystis pyrifera (M. pyrifera) in this study. The optimum experimental pretreatment condition (100°C, 30 min, 11.9 mM FeSO4) and the predicted optimum pretreatment condition (113.95°C, 29.1 min, 12.75 mM FeSO4) were identified using a central composite design method. All glucan and xylan were recovered as monosaccharides or polysaccharides without a fermentation inhibitor (e.g., hydroxymethyl furfural and furfural). The IHRHW-treated macroalgae digestibility reached 88.1% under the optimum experimental condition, whereas that under the predicted optimum condition reached 92.1%. The value was approximately threefold higher than those obtained with untreated M. pyrifera. Carbohydrate recovery and enzymatic hydrolysis can be significantly enhanced by the new economic hydroxyl radicals and hot water pretreatment.