Feedstock For Biodiesel Production Research Articles

Enhanced lipid production in Scenedesmus obliquus via nitrogen starvation in a two-stage cultivation process and evaluation for biodiesel production

The present study amalgamated the high lipid accumulation of Scenedesmus obliquus CCAP 276/3A and a FAME profile suitable for biodiesel production by optimization of nitrate concentration in a flat panel photobioreactor. In the proposed two-stage cultivation process, the nitrogen replete stage I was aimed at maximizing the biomass concentration, followed by a nitrogen deprived stage II for enhancing lipid production. Maximum lipid content was obtained when Scenedesmus obliquus was cultivated for 5 days under nitrogen limited stage II with nitrate concentration of 0.1 g/L. Lipid content ramped up from 33.1% (DCW) in control conditions to 45.1% (DCW) under the identified optimal conditions. The critical properties of biodiesel derived from this lipid were estimated based on the FAME composition; the results established the suitability of Scenedesmus obliquus CCAP 276/3A as a feedstock for biodiesel production. The present study provides important insights into the nitrogen response behavior of Scenedesmus obliquus which can help steer future schemes of lipid enhancement in algae.

Utilization of nano-sized waste lime sludge particles in harvesting marine microalgae for biodiesel feedstock production

Utilization of nano-sized waste lime sludge particles in harvesting marine microalgae for biodiesel feedstock production

Autophagy Induced Accumulation of Lipids in pgrl1 and pgr5 of Chlamydomonas reinhardtii Under High Light.

Chlamydomonas (C.) reinhardtii is a potential microalga for lipid production. Autophagy-triggered lipid metabolism in microalgae has not being studied so far from a mutant of proton gradient regulation 1 like (PGRL1) and proton gradient regulation 5 (PGR5). In this study, C. reinhardtii cells (wild-type CC124 and cyclic electron transport dependant mutants pgrl1 and pgr5) were grown photoheterotrophically in high light 500 μmol photons m–2 s–1, where pgr5 growth was retarded due to an increase in reactive oxygen species (ROS). The lipid contents were increased; however, carbohydrate content was decreased in pgr5. Further, the Nile Red (NR) fluorescence shows many lipid bodies in pgr5 cells under high light. Similarly, the electron micrographs show that large vacuoles were formed in high light stress despite the grana stacks structure. We also observed increased production of reactive oxygen species, which could be one reason the cells underwent autophagy. Further, a significant increase of autophagy ATG8 and detections of ATG8-PE protein was noticed in pgr5, a hallmark characteristic for autophagy formation. Consequently, the triacylglycerol (TAG) content was increased due to diacylglycerol acyltransferases (DGAT) and phospholipid diacylglycerol acyl-transference (PDAT) enzymes’ expression, especially in pgr5. Here the TAG synthesis would have been obtained from degraded membrane lipids in pgr5. Additionally, mono, polyunsaturated, and saturated fatty acids were identified more in the high light condition. Our study shows that the increased light induces the reactive oxygen species, which leads to autophagy and TAG accumulation. Therefore, the enhanced accumulation of TAGs can be used as feedstock for biodiesel production and aqua feed.

NOx–Smoke Trade-off Characteristics in a Palm Oil-Fueled CRDI Diesel Engine under Various Injection Pressures and EGR Rates

Palm oil is one of the most common and productive vegetable oils, so it is often used as an excellent feedstock for biodiesel production. However, due to the high viscosity and other issues of palm oil, it cannot be directly used as an alternative fuel for diesel engines unless some treatment is carried out. In this study, the effects of palm oil-diesel blend fuel on the nitrogen oxides (NOx)–smoke trade-off characteristics were investigated in a common rail direct injection (CRDI) diesel engine under various injection pressures and exhaust gas recirculation (EGR) rates. It was found that NOx and smoke from the combustion of fuel containing 50% palm oil (P50D50) were simultaneously suppressed by 3% and 3.1% compared with diesel fuel at an injection pressure of 400 bar, respectively. The performance of P50D50 was comparable to that of diesel, but at high injection pressure and high EGR rate, it showed shorter ignition delay (ID) and lower smoke emission.

Strategies for fuel property enhancement for second-generation multi-feedstock biodiesel

Fatty acids from non-edible bioresources are highly sought after as biofuel feedstock and the use of multi-stream feedstock for biodiesel production is of interest. This study explores the potential of using blended feedstock consisting of inedible jatropha oil (JO) and waste cooking oil (WO) for biodiesel production. Prior to blending, the unfavourable high acid value of jatropha oil was esterified under the most optimal conditions of 60 °C, 1% H2SO4 catalyst and alcohol to oil molar ratio of 11:1 to maximise the esterified yield (81.1 %). Based on the acid value measurement, the optimum volumetric blend of WO/EJO was determined to be 90/10 with the lowest acid value of 1.9 mg KOH g−1, which was then utilised as feedstock for base-catalysed transesterification. The KOH catalysed transesterification was optimised at 60 °C, 1 wt% KOH catalyst and alcohol to oil molar ratio of 6:1 to produce biodiesel with low acid value (0.2 mg KOH g−1), high calorific value (38.4 MJ kg−1), high oxidation stability (∼11 h) and favourable viscosity (4.7 mm2 s−1). The results show that the produced biodiesel has acceptable physicochemical properties but its properties can further be improved by blending with petroleum diesel and antioxidant. Among those produced blend derivatives, petroleum diesel and biodiesel blend (80:20) or B20 showed the best improvement with high calorific value (46.6 MJ/kg), high oxidation stability (∼37 h) and low acid value (0.3 mg KOH g−1). Based on the study, in situ feedstock blending of WO/EJO can improve the physicochemical properties of the produced biodiesel and reduce the dependency on single feedstock. Biodiesel blending with commercial diesel can enhance the biodiesel fuel properties and such derivatives can be directly applied in an existing engine.

Oligocat: Oligoesters as Pseudo-Homogenous Catalysts for Biodiesel Synthesis.

Biodiesel production from first-generation feedstock has shown a strong correlation with the increase in deforestation and the necessity of larger areas for land farming. Recent estimation from the European Federation for Transport and Environment evidenced that since the 2000s decade, an area equal to the Netherlands was deforested to supply global biodiesel demand, mainly originating from first-generation feedstock. Nevertheless, biodiesel is renewable, and it can be a greener source of energy than petroleum. A promising approach to make biodiesel independent from large areas of farming is to shift as much as possible the biodiesel production chain to second and third generations of feedstock. The second generation presents three main advantages, where it does not compete with the food industry, its commercial value is negligible, or none, and its usage as feedstock for biodiesel production reduces the overall waste disposal. In this manuscript, we present an oligomeric catalyst designed to be multi-functional for second-generation feedstock transesterification reactions, mainly focusing our efforts to optimize the conversion of tallow fat and sauteing oil to FAME and FAEE, applying our innovative catalyst. Named as Oligocat, our catalyst acts as a Brønsted-Lowry acid catalyst, providing protons to the reaction medium, and at the same time, with the course of the reaction, it sequesters glycerol molecules from the medium and changes its physical phase during the transesterification reaction. With this set of properties, Oligocat presents a pseudo-homogenous behavior, reducing the purification and separation steps of the biodiesel process production. Reaction conditions were optimized applying a 42 factorial planning. The output parameter evaluated was the conversion rate of triacylglycerol to mono alkyl esters, measured through gel permeation chromatography (GPC). After the optimization studies, a conversion yield of 96.7 (±1.9) wt% was achieved, which allows classifying the obtained mono alkyl esters as biodiesel by ASTM D6751 or EN 14214:2003. After applying the catalyst in three reaction cycles, Oligocat still presented a conversion rate above 96.5 wt% and as well an excellent recovery rate.

Application of Life Cycle Assessment Tool on Biodiesel Production: Assessing the Environmental Impact of Biodiesel

Bioenergy is an economic and ecological alternative energy, derived from biomaterials such as bioethanol, biomass, biodiesel etc. Therefore, biodiesel is a renewable and biodegradable fuel could be manufactured from vegetable oils, animal fats, or recycled restaurant grease. Traditionally world believes that the renewable energy has no impact on environment and ecology. Therefore, the key objective of this study is to assess the environmental undesirable impact associated with the production of biodiesel. The present research used the cooked oil (waste) as a feedstock for biodiesel production and assesses the life cycle impact of one ton of biodiesel. The life cycle of this product involves four stages including collection of feed stock, pre- treatment, transportation/ delivery stage and transesterification process. Waste oil was collected from food industry. After the pre-treatment of waste cooked oil, it was allowed for the transesterification process. The environmental impact was analyzed by SimaPro 7.1 software. Although, biodiesel is a renewable energy, one ton of biodiesel production contributes to the global warming potential around 287.3 kgCO2 eq. However, the amount is smaller than other conventional fuel such as fossil fuel and coal. Other environmental impacts such as Eutrophication, terrestrial eco-toxicity can be negligible. The transesterification stage is the main reason for the (69.27%) total environmental impacts.

Future prospects of biodiesel production from jatropha in India

India is vast country with an approximate population of around 138 crores as of 2020 according to United Nations data. The increase in population leads to the high demand of petroleum oils and gases which results in the increase in the price as well. The combustion of fossil fuels produces harmful emissions, which are also responsible for secondary pollutants such as smog, acid rain, and other harmful air pollutants. To overcome these situations, there is need of alternative and clean fuel. Among the available alternatives, biodiesel derived from non-edible plants have been considered a better option than petroleum diesel. Government of India has proposed to use 5% biodiesel produced from waste cooking oils and non-edible oils such as jatropha, karanja by 2030. This study presents the current scenario of jatropha as a feedstock for biodiesel production and how the flexibility in the growth of jatropha makes it suitable for India. With the development done so far by many investigators to establish jatropha biodiesel as potential substitute of diesel has also been covered in this article.

Sustainable and eco-friendly synthesis of biodiesel from novel and non-edible seed oil of Monotheca buxifolia using green nano-catalyst of calcium oxide

Presently, biodiesel offers a sustainable and renewable substitute for exhausting fossil fuels such as Petro-diesel. Large scale production of biodiesel could lead to positive outcomes in terms of environmental quality by reducing greenhouse gasses emission and Societal-Economic development. Hence, this research work focused on biodiesel synthesis from novel and non-edible seed oil of Monotheca buxifolia using green nano-particles of calcium oxide synthesized with aqueous leaves extract of Boerhavia procumbens. Advanced techniques like X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy diffraction X-Ray (EDX) were used to characterize calcium oxide nano-particles. High yield of biodiesel (95%) was obtained at optimum reaction conditions such as methanol to oil molar ratio of 9:1, catalyst loading 0.83 (wt.%), reaction time 180 min and temperature 85 °C. Gas Chromatography/Mass spectroscopy (GC/MS) analysis of biodiesel revealed four distinct peaks of methyl esters. Results of Fourier-transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance (NMR) confirmed the formation of methyl esters in biodiesel sample. Fuel properties of biodiesel such as density (0.821 kg/m3), viscosity (5.35 mm2/s), cloud point (-8 ◦C), pour point (-9 ◦C) and flash point (95 ◦C) were found equivalent to international ASTM D-6571, EN 14,214 and China GB/T 20828–2007 standards. It was finally concluded that Monotheca buxifolia is a highly potential, eco-friendly, and cheaper biomass feedstock for biodiesel production.

Simultaneous productions of biodiesel and biochar from krill

The Antarctic krill, referring to Euphausia superba, feeds phytoplankton, grown up with photosynthesis for CO2 fixation. Therefore, the use of krill as a raw feedstock for energy production is a highly carbon negative approach, not disturbing the food supply chain of human. Although the krill has high lipid content (up to 40 wt%, dry basis), its use as a raw feedstock for biodiesel production has not been considered. In this study, the feasibility of Euphausia superba to be used as a biodiesel feedstock was scrutinized. Prior to biodiesel production, an annual biodiesel production potential from the krill without disruption of ecosystems was estimated (129% larger than current biodiesel production in Korea). Because krill oil contains high fraction impurities, (trans)esterification with acid catalyst resulted in low yield of biodiesel (6.5 wt%), while non-catalytic transesterification achieved 94.7 wt% of biodiesel yield. To maximize the utilization of krill, solid residue obtained after biodiesel production was synthesized to krill biochars, and they were used as sorptive materials for adsorption of toxic chemicals. Among different model pollutants (Cd(II), Cr(VI), and methylene blue), krill biochar had the best adsorption capacity for Cd(II) (13.7 mg g−1), which is comparable value with other studies.

Fermentative reforming of crude glycerol to 1,3-propanediol using Clostridium butyricum strain L4

Repurposed used cooking oil is a sustainable alternative to other feedstocks for biodiesel production offering enviro-economic benefits. Residual crude glycerol (RCG) from such biodiesel production plants is difficult to utilize due to presence of numerous toxic impurities with various inhibitory effects on biological fermentative reforming process. However, it is a new industrial feedstock for bio-based production of 1,3-propanediol. In this work, a new Clostridium butyricum strain L4 was isolated from biogas reactor leachate after rigorous adaption and 35 subcultures under increasing stress conditions and studied for green production of 1,3-propanediol (PDO) from RCG and further process development. Evaluation of fermentative reforming kinetics was performed and the optimal reaction conditions are pH 7.0, temperature 30 °C, 2 g yeast extract/L and 15 g ammonium sulphate/L. Glycerol-glucose co-fermentation (10:1) enhanced cell growth and thus, PDO output by 11.6 g/L. In comparison to batch fermentation (24.8 g PDO/L; 0.58 mol PDO/mol glycerol) there was 2.8-fold improvement with fed-batch process resulting in accumulation of 70.1 g PDO/L (Yield = 0.65 mol PDO/mol glycerol) using the studied biocatalyst in 150 h. In order to predict yields under different operational conditions a multiple linear regression model was developed (r2 = 0.783) with six independent variables (p < 0.05), where biomass (g/L) and temperature (oC) were forecasted as top contributors to PDO yield. Finally, this biocatalyst appears as a potential candidate for industrial use due to its non-pathogenic nature, ability to grow in wide pH and temperature conditions, tolerance to high substrate and product concentration, insignificant generation of by-products and Coenzyme B12 independent biotransformation. The study can add value to bio-utilization of RCG to produce green 1,3-propanediol.

Property Determination, FA Composition and NMR Characterization of Palm Oil, Used Palm Oil and Their Methyl Esters

The search for a cost-effective, environmentally friendly and sustainable feedstock for biodiesel production has attracted attention among researchers. After frying, palm oil may become thermally degraded and unsuitable for consumption. In the current effort, neat palm oil (NPO), waste palm oil earlier utilized for frying fish and chips (WPOFC) and waste palm oil previously utilized to fry sausage and chips (WPOSC) were transesterified into waste palm oil methyl ester, namely, WPOMEFC and WPOMESC, respectively. The PO, WPOs and their ester derivatives were subjected to physicochemical properties, fatty acid (FA) compositions and 1H and 13C nuclear magnetic resonance (NMR) analyses. The thermal degradation, transesterification process and the foods the palm oil was used to fry affected the density, kinematic viscosity, acid value, pH, iodine value and FA profile of the samples. The outcome of the characterization reveals that the 1H and 13C NMR spectra of NPO, WPOFC and WPOSC show clear similarity, but NPO exhibits different intensities from that of the WPO samples. The absence of the peaks between δ 4.6 ppm and 5.0 ppm in the 1H NMR spectrum signifies the complete transformation of triglycerides in the WPO samples into biodiesel. The 13C NMR spectrum indicates the presence of ester carbonyl carbon (C=O) in WPOMEFC and WPOMESC, peculiar to ester, at a chemical shift ranging from 174.8 ppm to 174.9 ppm.

Integrating life cycle assessment and characterisation techniques: A case study of biodiesel production utilising waste Prunus Armeniaca seeds (PAS) and a novel catalyst

Prunus Armeniaca seed (PAS) oil was utilised as a waste biomass feedstock for biodiesel production via a novel catalytic system (SrO–La2O3) based on different stoichiometric ratios. The catalysts have been characterised and followed by a parametric analysis to optimise catalyst results. The catalyst with a stoichiometric ratio of Sr: La-8 (Sr–La–C) using parametric analysis showed an optimum yield of methyl esters is 97.28% at 65 °C, reaction time 75 min, catalyst loading 3 wt% and methanol to oil molar ratio of 9. The optimum catalyst was tested using various oil feedstocks such as waste cooking oil, sunflower oil, PAS oil, date seed oil and animal fat. The life cycle assessment was performed to evaluate the environmental impacts of biodiesel production utilising waste PAS, considering 1000 kg of biodiesel produced as 1 functional unit. The recorded results showed the cumulative abiotic depletion of fossil resources over the entire biodiesel production process as 22,920 MJ, global warming potential as 1150 kg CO2 equivalent, acidification potential as 4.89 kg SO2 equivalent and eutrophication potential as 0.2 kg PO43− equivalent for 1 tonne (1000 kg) of biodiesel produced. Furthermore, the energy ratio (measured as output energy divided by input energy) for the entire production process was 1.97. These results demonstrated that biodiesel obtained from the valorisation of waste PAS provides a suitable alternative to fossil fuels.

Microbial fuel cells with Photosynthetic-Cathodic chamber in vertical cascade for integrated Bioelectricity, biodiesel feedstock production and wastewater treatment

This study aimed to develop efficient microbial fuel cells (MFCs) for integrated bioelectricity, biodiesel feedstock production and wastewater treatment. Among wastewaters tested, MFC fed with anaerobic digester effluent from rubber industry gave the maximum power density (55.43 ± 1.08 W/m3) and simultaneously removed COD, nitrogen and phosphorus (by 72.4 ± 0.9%, 40.5 ± 0.8% and 24.4 ± 1.5%, respectively). 16S rRNA gene analysis revealed that dominant microbial communities were: Firmicutes (43.68%), Bacteroidetes (25.41%) and Chloroflexi (15.02%), which mostly contributed to bioelectricity generation. After optimizing organic loading rate, photosynthetic oleaginous microalgae were applied in cathodic chamber in order to increase oxygen availability, secondarily treat anodic chamber effluent and produce lipids as biodiesel feedstocks. Four MFCs with photosynthetic-cathodic chamber connected in vertical cascade could improve power density up to 116.9 ± 15.5 W/m3, sequentially treat wastewater, and also produce microalgal biomass (465 ± 10 g/m3) with high lipid content (38.17 ± 0.01%). These strategies may greatly contribute to sustainable development of integrated bioenergy generation and environment.

Two birds with one stone: A combined environmental and economic performance assessment of rapeseed‐based biodiesel production

AbstractRapeseed is the dominant feedstock for biodiesel production in Germany; however, significant decline in crop yields observed during the 2018 drought in Europe poses economic and environmental risks for its sustained use as a fuel crop. Many Life Cycle Assessment (LCA) studies were conducted to quantify the potential environmental impacts of biodiesel production; however, only a few studies have considered the spatial and temporal heterogeneities of the studied regions. Furthermore, previous studies have usually only focused on the greenhouse gas (GHG) savings of biodiesel and have ignored the environmental burden and economic profits of biodiesel production. For the first time, we combined the Regional Environmental LCA model with an economic analysis to evaluate both the environmental impact and the economic benefits of biodiesel production in Central Germany (CG). Our results showed that emissions from rapeseed cultivation were the largest contributor to both global and regional environmental impact categories. In our study region, we found that GHG emissions were around 56%–71% lower for rapeseed‐based biodiesel than for fossil fuels. Due to the drought in 2018, we also observed that the regional rapeseed supply could not meet the demand of biodiesel production in CG. An economic analysis of biodiesel production found significant economies of scale effect in the biodiesel industry. In addition, none of the studied biodiesel plants were able to operate at their designed installed capacities without causing indirect land‐use change. Furthermore, the profitability of biodiesel production was closely related to the feedstock cultivation cost. Based on these findings, we concluded that a regionalized LCA model would be able to more accurately evaluate the environmental influence of biodiesel production by taking site‐specific conditions into consideration. We also suggest that potential biodiesel plant operators take the regional biodiesel production density and feedstock cultivation conditions into account when deciding on plant size.

Biodiesel production and comparison using commercial lipase and chemical catalyst from Cassia auriculata oil

In this present investigation, Cassia auriculata was explored as a feedstock for production of biodiesel. Transesterification reaction was performed by both enzyme (lipase) and chemical (potassium hydroxide) catalyst with diverse acyl acceptors such as methanol, ethanol, propanol, n-propanol, butanol, n- butanol, and finally their biodiesel yield were also recorded. Process optimization was performed by both one factor at a time method and response surface method. The maximal biodiesel yield of 92% (weight/weight) was obtained at the following optimal conditions: Oil:Methanol molar ratio of 1:6 (moles/moles), the lipase concentration of 2% (weight/weight), at 35 ​°C and 120 ​min. The highest biodiesel yield from Cassia auriculata oil was occurred with excess methanol that aids the equilibrium shift in the forward direction. The kinetics of the transesterification reaction was investigated under optimal conditions and the activation energy was found to be 14.91 ​kJ/mol. Simultaneously Gas Chromatography – Mass Spectroscopy was also carried out for the biodiesel produced from Cassia auriculata and the same has been reported. The GC analysis declares the existence of fatty acid esters like hexadecanoic acid methyl ester, methyl stearate and the peak with retention time 12.8 ​min signifies the evidence of hexadecanoic acid methyl ester with 28% of yield content. This investigation also evaluated the biodiesel quality produced from lipase-transesterified Cassia auriculata oil based on fuel properties. Biodiesel properties Flash Point (FC), Pour Point (PP) and kinematic viscosity were compared with American (ASTM 6751) and European (EN 14214) Standards. Cassia auriculata oil had PP 6.7 ​°C and Kinematic viscosity (813 ​kg/m3) that agreed with both the standards. Thus this study showed that Cassia auriculata oil could be a better fuel alternative with further improvement of fuel properties.

Reconsidering the potential of direct microalgal biomass utilization as end-products: A review

Microalgae can rapidly sequester carbon dioxide (CO2) and convert it into various marketable products. Thus, these photosynthetic microorganisms have gained substantial attention as prospective biological platforms for the practical reduction of CO2 and establishing renewable and sustainable supply chains. However, conventional biomass applications to which attention has been directed, such as a feedstock for biodiesel production, are only achievable through cumbersome downstream processes, including extraction, fractionation, separation, and refinement. These stereotypical biomass utilization strategies have increased concerns regarding economic, energetic, and environmental viability. As a promising alternative, utilization of whole microalgal biomass as end-products has emerged because it can directly provide various beneficial commodities through a streamlined production route only consisting of harvesting and drying processes. The process review in this study clearly shows the energy and CO2 reduction efficiencies of this strategy compared with other traditional production routes. Despite the high potential, this application strategy has been overlooked because of the limited commercialized examples and the broad use of established methods. Recently, many applications have been suggested, and their practicality has been thoroughly verified according to the main biochemical constituents, namely carbohydrates, proteins, and lipids. Raw microalgal biomass produced by a potentially carbon-negative and net-energy-positive process can be employed as-is in an extensive range of fields that cover most human needs, including nutritious foods and feeds with bioactive functions, cosmetics, thermoplastic materials, and fuels for direct combustion. Thus, this comprehensive review aims to provide an opportunity to reconsider the potential and practicality of whole microalgal biomass utilization strategies.

In-situ (trans)esterification of lipid-dense post-hydrolysis rice bran at ambient pressures with low acid loading

Dilute acid hydrolysis was employed to generate lipid-dense post-hydrolyzed rice bran (PHRB) which was utilized as feedstock in biodiesel production. Upon drying of the wet PHRB with the entrained dilute acid solution, subsequent carbonization and sulfonation occurred with the material, incorporating significant amounts of sulfur in PHRB as sulfonic acid. The collected dry PHRB was utilized as feedstock in the in-situ (trans)esterification (ISTE) of its lipids to fatty acid methyl esters (FAME), whereby the available acid sites reduced the acid catalyst to be loaded in the reaction system. The optimum reaction conditions under ambient pressures were determined via the Taguchi method and the highest yield achieved was 22.38 ± 0.28 g FAME/100 g PHRB (82.31% conversion or reaction yield), and was achieved at 65 °C, SSR of 20 mL methanol/g dried PHRB, 12 h reaction time, and 5 wt% H2SO4 of the PHRB processed. The post-ISTE PHRB was found to still possess the catalytic activity and could be used for the esterification of oleic acid and methanol and appreciable stability. Finally, the FAME-rich product also exhibits free-radical scavenging activity, owing to the presence of bioactive components, which may provide better oxidative stability or could be further recovered as high-value by-products.

Fatty Acid Profile of Microalgal Oils as a Criterion for Selection of the Best Feedstock for Biodiesel Production

Microalgae are considered to be potentially attractive feedstocks for biodiesel production, mainly due to their fast growth rate and high oil content accumulated in their cells. In this study, the suitability for biofuel production was tested for Chlorella vulgaris, Chlorella fusca, Oocystis submarina, and Monoraphidium strain. The effect of nutrient limitation on microalgae biomass growth, lipid accumulation, ash content, fatty acid profile, and selected physico-chemical parameters of algal biodiesel were analysed. The study was carried out in vertical tubular photobioreactors of 100 L capacity. The highest biomass content at 100% medium dose was found for Monoraphidium 525 ± 29 mg·L−1. A 50% reduction of nutrients in the culture medium decreased the biomass content by 23% for O. submarina, 19% for Monoraphidium, 13% for C. vulgaris and 9% for C. fusca strain. Nutrient limitation increased lipid production and reduced ash content in microalgal cells. The highest values were observed for Oocystis submarina, with a 90% increase in lipids and a 45% decrease in ash content in the biomass under stress conditions. The fatty acid profile of particular microalgae strains was dominated by palmitic, oleic, linoleic, and linoleic acids. Nutrient stress increased the amount of saturated and unsaturated fatty acids affecting the quality of biodiesel, but this was determined by the type of strain.

Strategies for Improvement of Lipid Production by Yeast Trichosporon oleaginosus from Lignocellulosic Biomass.

Microbial lipids have similar fatty acid composition to plant oils, and therefore, are considered as an alternative feedstock for biodiesel production. Oleaginous yeasts accumulate considerable amounts of lipids intracellularly during growth on low-cost renewable feedstocks such as lignocellulosic biomass. In this study, we cultivated yeast Trichosporon oleaginosus on hydrolysate of alkaline pretreated corn cobs. Different process configurations were evaluated and compared, including separate hydrolysis and fermentation (SHF) with cellulase recycle and simultaneous saccharification and fermentation (SSF) in batch and fed-batch mode. At low enzyme loading, the highest lipid concentration of 26.74 g L−1 was reached in fed-batch SSF fed with 2.5% (g g−1) substrate. Batch SHF was conducted for four rounds with recycling the cellulase adsorbed on unhydrolyzed lignocellulosic biomass. Thirty percent of cellulase saving was achieved for rounds 2–4 without compromising productivity and lipid yield. The addition of Tween 80 to lignocellulosic slurry improved the hydrolysis rate of structural carbohydrates in pretreated lignocellulosic biomass. Furthermore, supplementing the growth medium with Tween 80 improved lipid yield and productivity without affecting yeast growth. Oleaginous yeast T. oleaginosus is a promising strain for the sustainable and efficient production of lipids from renewable lignocellulosic feedstock.