Biomass and lipid production from Nannochloropsis oculata growth in raceway ponds operated in sequential batch mode under greenhouse conditions

Process optimization of one-step direct transesterification and dual-step extraction-transesterification of the Chlorococcum-Nannochloropsis consortium for biodiesel production

In the present study, the efficacy of one-step direct transesterification (OSDT) and Dual-step extraction-transesterification (DSET) of Chlorococcum sp., Nannochloropsis sp., and their consortium was evaluated for fatty acid methyl ester (FAME) yield. Initially, the biomass yield and lipid content of the two strains and their consortium were estimated. Of the biomasses, the consortium showed a higher biomass yield of 1.41 g/L and lipid content of 30.2%, which is higher than the monocultures irrespective of the different biomass drying methods used. With regards to the FAME yield, OSDT and DSET have yielded almost similar quantities about 21 g/100g dried biomass. Of the different reaction conditions of OSDT tested, a higher FAME yield at 70-71% (based on lipid weight) was obtained at 75 °C reaction temperature, 3 h reaction time with a 2g sample size. Eventually, the fatty acid composition of consortium biomass revealed higher levels of saturated and monounsaturated fatty acids in the vicinity of 46 and 25%, respectively. Based on the results, it is concluded that OSDT is a promising method due to its low energy consumption, cost-effective and time-saving attributes for quality biodiesel production from the Chlorococcum-Nannochloropsis consortium.

Effect of phosphorus and sodium acetate on lipid accumulation from Ankistrodesmus sp. IFRPD 1061 in an open pond

Ankistrodesmus sp, has been comprehensively studied for their potential in the production of biodiesel due to their biomass productivity and high lipid content. This study examined the biomass productivity, and concentration, lipid productivity, and concentration, and lipid contents of Ankistrodesmus sp. IFRPD 1061 under several phosphorus concentrations. The optimum conditions were attained at 0.12 g/L KH2PO4. The highest lipid content reached to 35.950 ± 4.253% (w/w) in 22 days cultivation. An open pond cultivation system was used with the addition of 10 mM sodium acetate on every fourth day (0, 4, 8 and 12) of cultivation and KH2PO4 on twelfth day of cultivation. The obtained biomass productivity and concentration, lipid productivity and concentration and lipid content were 0.709 ± 0.027 g/L, 48.304 ± 1.894 mg/L/day, 0.214 ± 0.004 g/L 14.550 ± 0.215 mg/L/day and 30.154 ± 1.627% (w/w) in 14 days of cultivation, respectively. The results exhibited that addition of 10 mM sodium acetate and KH2PO4 may enhance lipid accumulation within algae cells in an open pond cultivation system.

Bio-fixation of flue gas from thermal power plants with algal biomass: Overview and research perspectives

Rate of energy production is reflecting growth of nations and most of energy produced from the coal and natural gas-based thermal power plants (TPPs). Flue gas (point sources of emission) are main exhaustible form of gases that come from thermal power plants and are continuously promoting climate change and various environmental problems in global scenario. The present available technologies of flue gas treatment are energy and cost-intensive process. Among the available techniques for fixation of flue-gases at sustainable part, microalgal bio-fixation of flue gas is an alternative promising and competent technology with assurance of eco-friendly path of low energy and low-cost solution for pollution abetment with production of value added products. According to mechanism involves during photosynthetic process of microalgae, it utilizes atmospheric CO₂ and CO₂ from flue gases for their growth. Past, present and future treatment technologies for flue gas with their challenges are discussed. Recent experimental studies and commercially available bioreactors are very particular for bio-fixation of flue gas from thermal power plants are also reviewed with their future perspectives. The commercial viability of process with specific microalgal strains and utilized biomass for further value-added products are suggested with future limitations.

Outdoor cultivation of the green microalga Chlorella vulgaris under stress conditions as a feedstock for biofuel

The present work investigated the potential of the green alga Chlorella vulgaris to produce high-quality biofuel under culture stress conditions. The cultivation was carried out in a 1000 l open plate tank system, which provides biomass yields comparable to open pond systems, but with less area needed. Algal biomass and lipid content were measured repeatedly. We compared the two solvent systems n-hexane and hexane/isopropanol (HIP) for extraction efficiency of lipids and applied three different extraction methods Soxhlet, soaking, and soaking followed by Soxhlet (soak-Sox). The combination of the HIP solvent and the soak-Sox provided the highest lipid yield (15.8 ± 0.174). Volumetric biomass and lipid productivity were 0.201 g l^-1 day^-1 and 31.71 mg l^-1 day^-1, respectively, whereas areal biomass and lipid productivity were 25.73 g m^-2 day^-1 and 4.066 g m^-2 day^-1, respectively. The fatty acid profile by means of gas chromatography resulted in seven fatty acids from C₁₂ to C₁₈. The most abundant fatty acid methyl esters (FAMES) were palmitic (C16:0), oleic (C18:1), and stearic (C18:0) acids. Lipid synthesis enhanced by optimizing the Kuhl growth medium with replacing nitrate by urea (50% N compared to the original recipe) increased salt content (10 g/l NaCl), ferrous sulfate (0.5 g/l), and sodium acetate addition (1 g/l). With regard to density, kinematic viscosity, gravity, pour point, flash point, and cetane number, the Chlorella-biodiesel comply with ASTM and EN standards thus pointing at the high potential of lipids synthesized by Chlorella as a feedstock for biodiesel production.

Biomass and lipid production from Chlorella vulgaris UTEX 26 cultivated in 2 m3 raceway ponds under semicontinuous mode during the spring season

A Chlorella vulgaris UTEX 26 semicontinuous culture was implemented in 2000 L raceways with M medium during spring season at greenhouse conditions. Areal biomass productivities between 20 and 26 g m^-2 d^-1 were reached on the third day. The maximal areal lipid productivity obtained was 6.1 g m^-2 d^-1 and an increment in the saturated fatty acids (SFA) proportion (C14-C18) was favored in comparison with the fatty acids obtained with M medium in photobioreactors of 1 L and photoperiod light:darkness 12:12 h. After the eighth day of the culture or biomass concentrations above 0.25 g L^-1, the microalgal cultures were prone to contamination by ciliates and amoebae, due to the sugars excreted by C. vulgaris UTEX 26. The periodical addition of NH₄HCO₃ to the microalgal culture maintained the ammonium concentration between 25 and 50 mg L^-1, which contributed to diminish the contamination risks by protozoa.

Euglena gracilis growth and cell composition under different temperature, light and trophic conditions

Background

Euglena gracilis, a photosynthetic protist, produces protein, unsaturated fatty acids, wax esters, and a unique β-1,3-glucan called paramylon, along with other valuable compounds. The cell composition of E. gracilis was investigated in this study to understand how light and organic carbon (photo-, mixo- and heterotrophic conditions) affected growth and cell composition (especially lipids). Comparisons were primarily carried out in cultures grown at 23 °C, but the effect of growth at higher temperatures (27 or 30 °C) was also considered.

Cell growth

Specific growth rates were slightly lower when E. gracilis was grown on glucose in either heterotrophic or mixotrophic conditions than when grown photoautotrophically, although the duration of exponential growth was longer. Temperature determined the rate of exponential growth in all cultures, but not the linear growth rate during light-limited growth in phototrophic conditions. Temperature had less effect on cell composition.

Cell composition

Although E. gracilis was not expected to store large amounts of paramylon when grown phototrophically, we observed that phototrophic cells could contain up to 50% paramylon. These cells contained up to 33% protein and less than 20% lipophilic compounds, as expected. The biomass contained about 8% fatty acids (measured as fatty acid methyl esters), most of which were unsaturated. The fatty acid content of cells grown in mixotrophic conditions was similar to that observed in phototrophic cells, but was lower in cells grown heterotrophically. Heterotrophic cells contained less unsaturated fatty acids than phototrophic or mixotrophic cells. α-Linolenic acid was present at 5 to 18 mg g^-1 dry biomass in cells grown in the presence of light, but at < 0.5 mg g^-1 biomass in cells grown in the dark. Eicosapentaenoic and docosahexaenoic acids were detected at 1 to 5 mg g^-1 biomass. Light was also important for the production of vitamin E and phytol.