Production of microbial oil with high oleic acid content by Trichosporon capitatum

Microbial oils with high unsaturated fatty acids content, especially oleic acid content, are good feedstock for high quality biodiesel production. Trichosporon capitatum was found to accumulate lipid with around 80% oleic acid and 89% total unsaturated fatty acids content on nitrogen-limited medium. In order to improve its lipid yield, effects of medium components and culture conditions on cell growth and lipid accumulation were investigated. Optimization of media resulted in a 61% increase in the lipid yield of T. capitatum after cultivation at 28 °C and 160 rpm for 6 days. In addition, T. capitatum could grow well on cane molasses and afford a lipid yield comparable to that on synthetic nitrogen-limited medium. The biodiesel from the microbial oil produced by T. capitatum on cane molasses displayed a low cold filter plugging point (−15 °C), and so T. capitatum might be a promising strain to provide lipid suitable for high quality biodiesel production.     

Chlorella sp.: A new strain with highly saturated fatty acids for biodiesel production in bubble-column photobioreactor

The biodiesel production from a naturally isolated strain of Chlorella in 2 L bubble-column photobioreactor was studied. The microalgal strain was isolated from the rice paddy-field soil samples during a screening program. After 17 days, at the end of exponential phase of growth, the total content of the lipids was extracted. The extracted fatty acids were first esterified and then identified using GC/MS analysis. Several types of fatty acid methyl esters (FAMEs) were identified in the isolated microalga and the presence of saturated fatty acids in Chlorella sp. MCCS 040 was approved. The composition of fatty acids in the studied species of microalga was mainly palmitic acid methyl ester, myristic acid methyl ester, stearic acid methyl ester and undecanoic acid methyl ester. This strain because of its highly saturated fatty acids content can be an ideal candidate for biodiesel production.     

Neochloris oleoabundans grown on anaerobically digested dairy manure for concomitant nutrient removal and biodiesel feedstock production

Microalgae have been investigated as a promising biodiesel feedstock; however, large-scale production is not currently cost-competitive with petroleum diesel, and its environmental impacts have received little attention. Using wastewater to supply nutrients for algal growth obviates synthetic fertilizer use, provides on-site nutrient removal, and reduces greenhouse gas emissions. In this work, anaerobically digested dairy manure was used to grow the oleaginous green alga Neochloris oleoabundans. In batch culture experiments with both synthetic media and anaerobic digester effluent, N. oleoabundans assimilated 90-95% of the initial nitrate and ammonium after 6 d and yielded 10-30% fatty acid methyl esters on a dry weight basis. Cellular lipid content and the N concentration in the growth media were inversely correlated. In addition, the proportion of polyunsaturated fatty acids (i.e. C16:3, C18:2, and C18:3) decreased with N concentration over time while the proportion of C18:1 fatty acid increased. Although N deficiency is likely the primary driver behind lipid accumulation, the influence of culture pH confounded results and requires further study. Other living microorganisms in the digester effluent were not observed to affect algal growth and lipid productivity, though the breakdown of organic nitrogen may have hindered lipid accumulation traditionally achieved through the manipulation of synthetic media. This work highlights the potential for waste-grown mono-algal cultures to produce high quality biodiesel while accomplishing simultaneous wastewater treatment.     

Culture of microalgal strains isolated from natural habitats in Thailand in various enriched media

Six freshwater microalgal strains in the class of Chlorophyceae, including Chlorococcum humicola, Didymocystis bicellularis, Monoraphidium contortum, Oocystis parva, Sphaerocystis sp., and Scenedesmus acutus were isolated from natural habitats in Thailand. The six strains were compared for their biomass yield, lipid content, and lipid productivity in four enriched culture media in batch mode. Significant differences were found across algal strains and culture media. The best strain was found to be C. humicola, which had the highest biomass yield of 0.113 g/l/d (in Kuhl medium), the highest lipid content of 45.94% (in BG-11 medium), and the highest lipid yield of 0.033 g/l/d (in 3NBBM medium). The 3NBBM medium, which has the lowest nitrogen concentration among the four culture media, was considered the optimal culture medium for C. humicola for lipid production. The fatty acid profile of C. humicola was also found to be affected by the culture medium. More oleic acid (C18:1) but less linolenic acid (C18:3) was accumulated in BG-11 and 3NBBM than in Kuhl and N-8 media. Lipid profiles of C. humicola were comparable to palm oil in the percentage of palmitic acid and the total amount of saturated fatty acids; however, C. humicola made more poly-unsaturated fatty acids such as linoleic (C18:2) and linolenic (C18:3) acids than oil palms. Lipids from C. humicola were believed to be acceptable for biodiesel production.     

Impact of light intensity,CO2 concentration and bubble size on growth and fatty acid composition of Arthrospira (Spirulina) platensis KMMCC CY-007

Studies on lipid accumulation and fatty acid composition of microalgae as a feedstock for biodiesel have been reported in numerous papers in recent years. However, in contrast to microalgae, documentation on cyanobacteria such as Arthrospira platensis with regard to lipid production has been sparse thus far. In this paper, we show the relatively high lipid accumulation potential of A. platensis KMMCC CY-007 in modified Schlösser medium. Four different growth conditions [7.5 candela (cd) and 1% CO₂, 15 cd and 1% CO₂, 7.5 cd and air, and 15 cd and air] were examined over 7 days in order to compare the impact of light intensity. Using two different growth conditions (7.5 cd and 1% CO₂ bulk bubble and 7.5 cd and 1% CO₂ fine bubble), changes in growth, lipid accumulation and fatty acid composition were compared. The highest lipid content of 37.96% was obtained at 7.5 cd and 1% CO₂ fine bubble after 7 days, and the maximum net production (72.56%) of long chain fatty acid methyl esters (C16:0 and C18:0) detected at 7.5 cd and 1% CO₂ bulk bubble. These data suggest the potential of A. platensis for production of crude lipid as a future feedstock for biodiesel production.     

Biomass and lipid productivities of marine microalgae isolated from the Persian Gulf and the Qeshm Island

In this work, the screening of 147 microalgal strains from the Persian Gulf and the Qeshm Island (Iran) were done in order to choose the best ones, in terms of growth (biomass) rate and lipid content for biodiesel production. A methodology, combining experiments in lab-scale and pilot plant (open pond) used to produce and evaluate biomass and lipid productivity is presented for the systematic investigation of the potential of different microalgae species. The culture conditions, including photo flux (180 ??E m⁻² s⁻¹), photoperiod (12 h light/dark), temperature (25 °C), pH (≈8), air (carbon dioxide) and growth medium, were kept constant for all experiments. Microalgae were screened in two stages using optical density (for evaluation of biomass concentration) and Nile red and gas chromatography (for determination of lipid content and fatty acid fractions). In general, maximum specific growth rate and the maximum biomass productivity were obtained after 8-12-day culture. Nannochloropsis sp. and Neochloris sp. were selected from the marine microalgal culture collection, due to their high biomass (50 and 21.7 g L⁻¹, respectively) and oil content (52% and 46%, respectively). If the purpose is to produce biodiesel only from one species, Nannochloropsis sp. presented the most adequate fatty acid profile, namely linolenic and other polyunsaturated fatty acids. However, the microalgae Chlorella sp. can also be used if associated with other microalgal oils. In addition, selected strains could be potent candidates for commercial production in the open pond culture.     

Bioconversion of organic wastes into biodiesel and animal feed via insect farming

Approximately one-third of all food produced for human consumption worldwide is wasted. The current waste management practices are not only costly but also have adverse impact on environment. In this study, black soldier fly (BSF) (Hermetia illucens) larvae were grown on food wastes to produce fat and protein-rich BSF prepupae as a novel strategy for efficient organic waste management. The lipid content in BSF prepupae was characterized for fatty acids profile. Whole BSF prepupae, pressed cake, and meal were analyzed for important animal feed characteristics. BSF-derived oil has high concentration of medium chain saturated fatty acids (67% total fatty acids) and low concentration of polyunsaturated fatty acids (13% total fatty acids), which makes it potentially an ideal substrate for producing high quality biodiesel. BSF (prepupae, pressed cake, and meal) has feed value comparable to commercial feed sources. Thus, the bioconversion of organic waste into BSF prepupae has significant potential in generating high-value products with simultaneous waste valorization.     

Co-production of biodiesel and alpha-linolenic acid (omega-3 fatty acid) from microalgae,Desmodesmus sp. MCC34

Microalgae are a potential source of biofuel and nutraceuticals. In the present study, Desmodesmussp. MCC34 was identified as a promising species for biodiesel and omega-3 fatty acid productions after initial screening since it had displayed the highest lipid productivity of 15.9 mg L^?1 day^?1 and alpha-linolenic acid of 24% of total fatty acids. Using silver ion chromatography, 92% of pure alpha-linolenic acid was selectively removed from total lipid of Desmodesmussp. MCC34, while the residual oil having a higher amount of saturated and monounsaturated fatty acids displayed biodiesel property adhering to international standards, suggesting fuel co-application.

Abbreviations: ALA: alpha-linolenic acid methyl ester; GLAME: gamma-linolenic acid methyl ester; FAME: atty acid methyl ester; SFA: aturated fatty acid; MUFA: monounsaturated fatty acid; PUFA: polyunsaturated fatty acid.     

Biomass and lipid production of marine microalgae using municipal wastewater and high concentration of CO2

In order to reduce the cost of the production of microalgae for biodiesel, the feasibility of using the mixture of seawater and municipal wastewater as culture medium and CO₂ from flue gas for the cultivation of marine microalgae was investigated in this study. Effects of different ratios of municipal wastewater and 15% CO₂ aeration on the growth of Nannochloropsis sp. were examined, and lipid accumulation of microalgae was also studied under nitrogen starvation and high light. It was found that optimal growth of microalgae occurred in 50% municipal wastewater, and the growth was further significantly enhanced by aeration with 15% CO₂. When Nannochloropsis sp. cells were transferred from the first growth phase to the second lipid accumulation phase under the combination of nitrogen deprivation and high light, both biomass and lipid production of Nannochloropsis sp. were significantly increased. After 12 days of the second-phase cultivation, the biomass concentration and total lipid content increased from 0.71 to 2.23 g L⁻¹ and 33.8–59.9%, respectively. This study suggests that it is possible to utilize municipal wastewater to replace nutrients in seawater medium and use flue gas to provide CO₂ in the cultivation of oil-bearing marine microalgae for biodiesel.     

Analytical evaluation of different carbon sources and growth stimulators on the biomass and lipid production of Chlorella vulgaris – Implications for biofuels

The key challenges in lipid production from marine microalgae include the selection of appropriate strain, optimization of the culture conditions and enhancement of biolipid yield. This study is aimed at evaluating the optimal harvest time and effect of chlorella growth factor (CGF) extract, carbon sources and phytohormones on the biomass and lipid production in Chlorella vulgaris. CGF, extracted using hot water from Chlorella has been reported to possess various medicinal properties. However, in the present study, for the first time in C. vulgaris, CGF was found as a best growth stimulator by enhancing the biomass level (1.208 kg m⁻³) significantly on day 5. Gibberellin and citrate augmented the biomass by 0.935 kg m⁻³ and 1.025 kg m⁻³. Combination of CGF and phytohormones were more effective than CGF and carbon sources. Analysis of fatty acid methyl esters indicated that the ratio of saturated to unsaturated fatty acids is higher in cytokinin, abscisic acid and CGF, and are also rich in short chain carbon atoms, ideal criteria for biodiesel. Nitrogen starvation favoured synthesis of more unsaturated fatty acids than saturated. This study shows that CGF enhances the biomass and lipid significantly and thus can be used for large scale biomass production.     

The reuse of waste cooking oil and spent bleaching earth to produce biodiesel

Currently, semi-refined and refined vegetable oils are used as a feedstock in biodiesel production. However, criteria such as competition with conventional fossil fuel, economic reasons, shortage supply of food and its social impact on the global scale have somewhat slowed the development of the biodiesel industry. Spent bleaching earth is currently under-utilized by deposition in landfills with no attempt to recover the oil. In this study the waste oil adsorbed on spent bleaching earth, refined soybean oil, and waste cooking oil were evaluated as potential sources of biodiesel production in Iran. Different characteristics of the oil samples, such as fatty acid composition, peroxide, iodine, acid values, etc., were evaluated. A two-step esterification reaction using methanol was conducted to produce biofuel. Subsequently, physicochemical properties of produced biodiesel were analyzed. The oil content in spent bleaching earth was 19.3%, which was lowered to 3.7% using hexane as the solvent. Gas chromatography showed that palmitic, oleic, and linoleic acids were predominantly fatty acids, respectively, and the highest content of saturated acids belonged to waste cooking oil (24%). The acidity of 8.3% was obtained for the oil recovered from spent bleaching earth followed by waste cooking oil (3.6%) and refined soybean oil (0.1%). Totally, the specifications of all biodiesel produced were in the range defined by ASTM D6751 and EN 14214 standards. Since about 2000–3000 tones of spent bleaching earth residual oil is annually dumped and the amount of waste cooking oil produced yearly is 500,000 tones, there is a great potential for Iran to produce biodiesel from waste oils.     

Development of low‐temperature properties on biodiesel fuel: a review

The use of biodiesel as a diesel fuel alternative is rapidly increasing. An important aspect of applying this alternative is the transportation and application in cold weather. In this article, different kinds of methods and technologies were briefly reviewed to improve the low‐temperature properties of biodiesel. The compositions of fatty acids would be effectively changed by choosing available material with high content of unsaturated fatty acids or by reducing saturated fatty acids via winterization process. Branched alcohols can be used to change biodiesel structures that improve the low‐temperature properties. As a technically feasible method, there is still a constant demand to search cost‐effective raw materials for economic branched alcohols production. In order to enhance the impact of crystal morphology and decrease freezing point, the blending chemical additives and petroleum fuels would be a promising method that have been widely used. Besides, other treatments such as epoxidation, hydroisomerization, and ozonization were also discussed. However, each method applied for improving low‐temperature properties of biodiesel should be effective and economical so that the biodiesel would continue to compete with fossil and other renewable fuels for market share. Copyright © 2015 John Wiley & Sons, Ltd.     

Biodiesel potential of the seed oils from some Brazilian native Euphorbiaceae species

In the present study, the oil content, fatty acid composition and physicochemical properties of seed oils and biodiesel from seven species of Euphorbiaceae were analyzed. The oil content from seven Brazilian native Euphorbiaceae species ranged from 25.4 to 48.5%. Nine primarily unsaturated fatty acids were identified in seed oils. Actinostemon concolor and Stillingia trapezoidea seeds accumulated mainly oleic and linoleic acids, whereas in the seeds of Croton floribundus, Croton nepetifolius, Euphorbia comosa and Microstachys corniculata, linoleic and linolenic acids were the main constituents identified. Palmitic and oleic acids were predominantly detected in the seeds of Sapium glandulosum. In general, the oils showed low acidity, viscosity and free fatty acids. The results suggest that the seed oils from A. concolor, S. glandulosum and S. trapezoidea might be a viable alternative for biodiesel production, while those from C. floribundus, C. nepetifolius, E. comosa and M. corniculata seeds have great potential for application in the paint, varnish and lubricant industries. Due to the high content of saturated fatty acids, the seeds of S. glandulosum could also be used to produce soaps and detergents. For most species analyzed, the biodiesel specifications are in accordance with EN 14214 and ASTM D6751 standards.     

Effect of outdoor conditions on the growth and lipid accumulation of six green algae

Microalgae are considered as an alternative feedstock for producing biodiesel. In this study, six oil-producing algae were cultivated with natural sunlight outdoors. The highest lipid content, biomass productivity, and lipid productivity were 29.99%, 208.42 mg/l/d, and 69.84 ml/d, respectively. In addition, the photosynthetic efficiency of PS II (Fv/Fm) was kept high during the cultivation and the preferred fatty acids (C16–C18) for producing biodiesel were more than 95% of total fatty acids for all of the strains.     

Comparative study of biohydrogen production by four dark fermentative bacteria

Dark fermentation is a promising biological method for hydrogen production because of its high production rate in the absence of light source and variety of the substrates. In this study, hydrogen production potential of four dark fermentative bacteria (Clostridium butyricum, Clostridium pasteurianum, Clostridium beijerinckii, and Enterobacter aerogenes) using glucose as substrate was investigated under anaerobic conditions. Batch experiments were conducted to study the effects of initial glucose concentration on hydrogen yield, hydrogen production rate and concentration of volatile fatty acids (VFA) in the effluents. Among the four different fermentative bacteria, C. butyricum showed great performance at 10 g/L of glucose with hydrogen production rate of 18.29 mL-H₂/L-medium/hand specific hydrogen production rate of 3.90 mL-H₂/g-biomass/h. In addition, it was found that the distribution of volatile fatty acids was different among the fermentative bacteria. C. butyricum and C. pasteurianum had higher ratio of acetate to butyrate compared to the other two species, which favored hydrogen generation.     

Oleaginous yeast Cryptococcus curvatus culture with dark fermentation hydrogen production effluent as feedstock for microbial lipid production

Volatile fatty acids (VFA) from dark fermentation hydrogen production were tested as carbon sources for the culture of oleaginous yeast Cryptococcus curvatus, which is a promising feedstock for biofuel production. The optimal acetate concentration and pH were investigated when potassium acetate was used as the sole carbon source. Comparisons were then made when hydrogen production effluent (HPE) from synthetic wastewater was tested as feedstock. A pH-stat culture fed with acetic acid ultimately produced 168 g/L biomass, with a lipid content of 75.0%. No inhibitor to yeast growth was produced in the hydrogen production process. However, inhibition occurred in culture with HPE from food waste (FW), indicating that inhibitors may be present in the original raw food waste. This inhibition could be avoided by a process that uses glucose as the initial carbon source and then is continuously fed with FW-HPE. The biomass productivity in this continuous culture process reached 0.34 g/L/h, but the lipid content was only 13.5%. These results suggest that FW-HPE alone is not an optimal feedstock, but HPE derived from nitrogen-deficient waste streams could be good feedstocks. This study provides preliminary evidence for the feasibility of using organic waste for the co-production of hydrogen and lipid.     

Analysis of performance and emission patterns of novel biofuel feedstock neat coconut fatty acid distillate (CFAD) fuelled single-cylinder diesel engine

This study examined the potential of using coconut fatty acid distillate (CFAD), a by-product of the processing of edible oils, as a diesel engine fuel. The major novelty of this study is to assess the CFAD as a viable feedstock of biodiesel to address global energy demands. CFAD has not been specifically researched as a feedstock for producing biodiesel or as a fuel for diesel engines, despite the fact that numerous studies on the production and performance of biodiesel have already been conducted. Fourier transform infrared (FTIR) spectroscopy, gas chromatography (GC), and FTIR were used to analyze the fuel. According to the results of the GC test, CFAD oil contains 91.53% saturated fatty acids, compared with only 8.47% unsaturated fatty acids. High saturation values can be seen in myristic acid (16.92%) and lactic acid (45.33%). Longer hydrocarbon chain lengths indicate higher energy density and boiling point, which also indicate lesser volatility. At a frequency of 1708.54 cm⁻¹, C─H stretching vibrations have been identified through FTIR investigation. The vibrations of C─C stretching at 1465.47 cm⁻¹ indicate the presence of alkenes/fingerprint phase. The blends used for this investigation include 90% diesel with 10% CFAD (CFAD10), 80% diesel with 20% CFAD (CFAD20), 70% diesel with 30% CFAD (CFAD30), and 100% CFAD. The CFAD 10%, 20%, and 30% blends as well as the CFAD100 had brake thermal efficiency values of 27.24%, 26.23%, 24.88%, and 21.52%, correspondingly, at full load. The average increment in brake-specific energy consumption for CFAD10, CFAD20, CFAD30, and CFAD100 over diesel fuel was 8.23%, 10.88%, 13.77%, and 25.90%, respectively. The behavior of CFAD exhibits reduced cylinder pressure because of the large content of moderate saturated fatty acids in this substance. The net heat release rate (NHRR) and cylinder pressure have a similar relationship in that the NHRR increases with increasing diesel volume. In comparison to diesel, the CO emissions from the CFAD20, CFAD30, and CFAD100 blends increased by 10.79%, 16.66%, and 35.89% at maximum load, respectively. It has been reported that NO_x is reduced more significantly the more CFAD is present in the mixture. The blend CFAD10 had the least amount of smoke. The high viscosity of the CFAD and its blends influences the fuel droplets range and the development of spray in the cylinder, which results in delayed combustion and higher unburned hydrocarbon emissions.     

Ethyl levulinate: A potential bio-based diluent for biodiesel which improves cold flow properties

Biodiesel, defined as mono-alkyl esters of long-chain fatty acids derived from vegetable oils or animal fats, is an attractive renewable fuel alternative to conventional petroleum diesel fuel. Biodiesel produced from oils such as cottonseed oil and poultry fats suffer from extremely poor cold flow properties because of their high saturated fatty acid content. In the current study, Ethyl Levulinate (ethyl 4-oxopentanoate) was investigated as a novel, bio-based cold flow improver for use in biodiesel fuels. The cloud (CP), pour (PP), and cold filter plugging points (CFPP) of biodiesel fuels prepared from cottonseed oil and poultry fat were improved upon addition of ethyl levulinate at 2.5, 5.0, 10.0, and 20.0% (vol). Reductions of 4-5 °C in CP, 3-4 °C in PP and 3 °C in CFPP were observed at 20 vol % ethyl levulinate. The influence of ethyl levulinate on acid value, induction period, kinematic viscosity and flash point was determined. The kinematic viscosities and flash points decreased with increasing content of ethyl levulinate. All samples (≤15 vol % ethyl levulinate) satisfied the ASTM D6751 limit with respect to flash point, but none of the 20 vol % blends were acceptable when compared to the higher EN 14214 specification. Acid value and oxidative stability were essentially unchanged upon addition of ethyl levulinate. In summary, ethyl levulinate appears acceptable as a diluent for biodiesel fuels with high saturated fatty acid content.     

Metabolomics of photobiological hydrogen production induced by CCCP in Chlamydomonas reinhardtii

The green alga Chlamydomonas reinhardtii can produce hydrogen gas (H₂) in the presence of the proton uncoupler carbonyl cyanide m-chlorophenyl hydrazone (CCCP). The addition of 15 μM CCCP to the algal cultures led to 13-fold increase in H₂ photoproduction compared to the control cultures without CCCP treatment. CCCP completely inhibited the photochemical activity of photosystem (PS) II under illumination. In order to better understand metabolic conditions necessary for sustained H₂ production, we have used gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF) for metabolomics analysis that is independent of nutritional stress, specifically, sulfur deprivation, which had been used previously to induce H₂ photoproduction. Even 10 min after addition of CCCP, metabolites from many metabolic modules were found drastically decreased, including levels of free amino acids, unsaturated free fatty acids and nucleotides. During prolonged CCCP exposure H₂ production was found to be stable for at least 12 h with a continued increase in levels of free fatty acids. These results indicate that CCCP might become a useful treatment for production of biohydrogen in reactors. The increase in fatty acid production might then be a useful addition for production of carbon-derived biofuels.     

Biohydrogen production by Lyngbya perelegans: Influence of physico-chemical environment

Biohydrogen production by a non-heterocystous cyanobacterium Lyngbya perelegans was studied under varied physico-chemical conditions including oxic/anoxic, light/dark period, light intensity, temperature, pH and salinity. Some important biological characteristics of the species that favored its selection as a hydrogen producing organism included its dense biomass in the culture, moderately good chlorophyll-a and carotenoid concentrations, high glycogen content, and high hydrogenase activity at its mid log phase (7d). Biohydrogen production by the cyanobacterium was found to be significantly influenced by its physico-chemical environment. H₂ production by the species could be increased 1.4 times by optimizing the light/dark duration, light intensity, pH and temperature, while maintaining anoxic conditions and supplementing the medium with a low concentration of salt.