Use Of Crude Glycerol Research Articles

Itaconate Production from Crude Substrates with U. maydis: Scale-up of an Industrially Relevant Bioprocess

BackgroundIndustrial by-products accrue in most agricultural or food-related production processes, but additional value chains have already been established for many of them. Crude glycerol has a 60% lower market value than commercial glucose, as large quantities are produced in the biodiesel industry, but its valorisation is still underutilized. Due to its high carbon content and the natural ability of many microorganisms to metabolise it, microbial upcycling is a suitable option for this waste product.ResultsIn this work, the use of crude glycerol for the production of the value-added compound itaconate is demonstrated using the smut fungus Ustilago maydis. Starting with a highly engineered strain, itaconate production from an industrial glycerol waste stream was quickly established on a small scale, and the resulting yields were already competitive with processes using commercial sugars. Adaptive laboratory evolution resulted in an evolved strain with a 72% increased growth rate on glycerol. In the subsequent development and optimisation of a fed-batch process on a 1.5-2 L scale, the use of molasses, a side stream of sugar beet processing, eliminated the need for other expensive media components such as nitrogen or vitamins for biomass growth. The optimised process was scaled up to 150 L, achieving an overall titre of 72 g L− 1, a yield of 0.34 g g− 1, and a productivity of 0.54 g L− 1 h− 1.ConclusionsPilot-scale itaconate production from the complementary waste streams molasses and glycerol has been successfully established. In addition to achieving competitive performance indicators, the proposed dual feedstock strategy offers lower process costs and carbon footprint for the production of bio-based itaconate.

Activated Carbon Electrodes Obtained from Crude Glycerol for Capacitive Deionization Desalination

The freshwater demand increases over the years to attend agriculture, industry, and human consumption demand. Water desalination by capacitive deionization (CDI) would be an interesting strategy to provide freshwater for populations suffering of water scarcity in arid and semi-arid regions in which brackish groundwater is available. CDI is an electrochemical technique based on the removal of ions using carbon electrodes. Besides low-cost, activated carbons (AC) produced from renewable sources are also desired due to sustainability demands. In parallel, appropriate routes for disposal or reuse of crude glycerol from biodiesel plants are also a major current concern (10 kg of biodiesel generates ~1.0 kg of glycerol). So, considering the water-waste nexus concept, in this work we proposed the use of crude glycerol as precursor to obtain a new sustainable activated carbon (PGAC), which was employed as an electrode for CDI desalination of brackish water. The crude glycerol is firstly converted to polyglycerol, which is carbonized and then chemically activated. The best desalination performance using the PGAC electrodes was achieved using membrane CDI configuration, applying 1.6 V, providing a stable salt adsorption capacity (SAC) of 27.1 mg of NaCl removed per g of PGAC over 50 desalination cycles. At this condition, co-ion repulsion is minimized and the charging efficiency (QE ) remained close to 100%. The high values of SAC and QE , along with the low cost of PGAC electrode, led to a very low specific energy consumption (2.6 J per mg of NaCl removed), compared to other values reported in literature, making it a potential candidate for use in CDI desalination. In order to further improve the desalination performance, a new cell architecture was proposed, named percolation flow cell (PFC). The PFC cell combines the fast mass transfer rates of the flow-through cell (FTC) configuration and longer residence time of flow-by cells (FBC), in which the flow velocity and electric current fields are perpendicular. Taking advantage of the beneficial aspects of the FBC and FTC designs, the desalination carried out using the PFC was enhanced by 170 %, providing a remarkable water desalination rate of 1661 mg g-1 day-1 at 1.0 mA cm-2 and single pass operation (7.0 mL min-1). Despite these advantages, the high pressure drop (0.12 bar cm-1) imposes a challenging issue for the effective application of PFE cells.

Valorisation of crude glycerol in the production of liquefied lignin bio-polyols for polyurethane formulations

Bio-polyols, produced by liquefying lignin with polyhydric alcohols, offer a promising alternative to conventional polyols for polyurethane production. To enhance the sustainability on the production of these bio-polyols, this study proposes the use of crude glycerol and microwave-assisted liquefaction as substitutes for conventional methods and commercial glycerol. This approach reduces the energy requirements of the reaction while also adding value to this by-product. The synthesis of bio-polyols with suitable properties to produce elastic and rigid polyurethane was carried out using previously optimised reaction conditions. Organosolv lignins obtained from Eucalyptus globulus and Pinus radiata were employed, using polyethylene glycol and crude glycerol as solvents and sulphuric acid as a catalyst. Several parameters of the bio-polyols were analysed, including hydroxyl number (IOH), acid number (An), and functionality (f), suggesting that the bio-polyols were suitable for polyurethane synthesis. Bio-polyols formulated to produce rigid polyurethanes exhibited IOH values of 554 and 383 (mg KOH/g), An values of 1.91 and 4.21 (mg KOH/g), and functionalities of 4.16 and 3.14 for Eucalyptus globulus and Pinus radiata lignin. In the case of bio-polyols for elastic polyurethanes, the values were 228 and 173 (mg KOH/g) (IOH), 20.94 and 25.09 (mg KOH/g) (An), and functionalities of 3.51 and 2.08.

Use of crude glycerol for mixotrophic culture of Phaeodactylum tricornutum

Crude glycerol is a waste stream from biodiesel production, which has previously been shown to be useable for mixotrophic cultivation of microalgae; however, at high concentrations the presence of contaminants may limit culture growth. In this study two previously identified methods of contaminant removal from crude glycerol were trialled for use in mixotrophic culture of Phaeodactylum tricornutum. Neither crude glycerol without contaminant removal, nor crude glycerol which has had contaminants removed through calcium precipitation, lead to culture growth of P. tricornutum. However, pH adjusted crude glycerol gave comparable cell densities (6.03 ± 0.24 × 106 cells ml−1 compared to 5.66 ± 0.15 × 106 cells ml−1), growth rates (3.25 ± 0.26 days compared to 2.85 ± 0.21 days) and fatty acid profiles compared to reagent grade glycerol. There were alterations in the carbon partitioning of the microalgae, in addition to changes in cell widths. Cell widths increasing when harvested at stationary phase, compared to reagent grade glycerol (4.88 compared to 4.28 μm), while chlorophyll (11.38 compared to 6.25 %DW) and carbohydrate contents decreased (17.29 compared to 14.15 %DW respectively). As a result, it can be concluded that this method of contaminant removal meant that crude glycerol may be successfully used for culture of P. tricornutum, which may reduce the costs of microalgal culture, depending upon the end use.

Carbon dioxide mitigation and biodiesel production by a marine microalga under mixotrophic mode by using transesterification by-product crude glycerol: A synergy of biofuels and waste valorization

The present work integrates carbon sequestration and waste reclamation with biofuel production into a single dynamic for encouraging eco-friendlier approaches ensuring environmental sustainability. To achieve improved carbon capturing and lipid production, a marine microalga Picochlorum soloecismus was selected. The maximum productivities of biomass and lipid were asserted to be 0.24 ± 0.02 gL−1d−1 and 58.2 ± 0.2 mgL−1d−1 under a CO2 supply of 17.0% at 0.7 vvm aeration in a 5 L photobioreactor under photoautotrophic condition. A low-priced mixotrophic medium was designed using CO2 with the transesterification by-product, i.e., crude glycerol. This produced maximum biomass and lipid productivities of 0.67 ± 0.04 and 0.13 ± 0.01 gL−1d−1 at a carbon fixation rate of 0.77 ± 0.06 gL−1d−1. The effect of mixotrophy was also investigated on a modified culture medium, i.e. Optimized ASN (Artificial Seawater Nutrient) prepared in our recent study generating a maximum lipid productivity of 0.31 ± 0.02 gL−1d−1at a carbon fixation rate of 0.80 ± 0.07 gL−1d−1. The use of crude glycerol in place of commercial glycerol for mixotrophy can reduce the medium cost by 22-fold. The methyl ester profile of biodiesel obtained under mixotrophy exhibited higher proportion of saturated fats and lower fraction of unsaturated fats. The fuel parameters lied within the established biodiesel standards.

Direct production of polyhydroxybutyrate and alginate from crude glycerol by Azotobacter vinelandii using atmospheric nitrogen

While biodiesel is drawing attention as an eco-friendly fuel, the use of crude glycerol, a byproduct of the fuel production process, has increasingly become a concern to be addressed. Here we show the development of a low-cost fermentation technology using an atmospheric nitrogen-fixing bacterium to recycle crude glycerol into functional biopolymers. Azotobacter vinelandii showed substantial growth on tap water-diluted crude glycerol without any pretreatment. The number of viable A. vinelandii cells increased over 1000-fold under optimal growth conditions. Most of the glycerol content (~ 0.2%) in the crude glycerol medium was completely depleted within 48 h of culture. Useful polymers, such as polyhydroxybutyrate and alginate, were also produced. Polyhydroxybutyrate productivity was increased ten-fold by blocking the alginate synthesis pathway. Although there are few examples of using crude glycerol directly as a carbon source for microbial fermentation, there are no reports on the use of crude glycerol without the addition of a nitrogen source. This study demonstrated that it is possible to develop a technology to produce industrially useful polymers from crude glycerol through energy-saving and energy-efficient fermentation using the atmospheric nitrogen-fixing microorganism A. vinelandii.

Emulsion-based drilling fluids: Rheological properties preservation facing changes on the temperature, pressure and dispersed phase

The biodiesel transesterification reaction generates crude glycerol as a by-product, which has been excessively generated due to the growing production of this biofuel. The possibility of allocating this low value-added waste to applications would solve several problems, especially regarding the need to dispose of this material. In this sense, the use of crude glycerol in olefin-based inverse emulsion fluids is something new in the literature. However, its performance in drilling fluids must ensure that the fluid's rheological properties are achieved. For this purpose, the plastic viscosity, yield stress and thixotropy of olefin-based fluids were studied, varying the temperature, pressure and the composition of the dispersed phase (sodium chloride brine (NaCl), crude glycerol and pure glycerol). A 23 factorial design was also carried out to assess whether the dispersed phase type, pressure and temperature variables affect the rheological properties of these fluids. The results showed that crude glycerol maintains the rheological properties of the conventional NaCl brine fluid even with changes in temperature and pressure, enabling the use of this industry waste for this type of application.

Improvement of the Crude Glycerol Purification Process Derived from Biodiesel Production Waste Sources through Computational Modeling

Considering waste as a possible new resource for useful purposes is one of the strategies included in the circular economy principles. In fact, industrial processes are seen as great contributors to the formation of waste streams. With the aim to attain more sustainable and resilient systems, in this study, a process flow chart was elaborated in an Aspen Plus computer simulator, to obtain the production of pure glycerol from crude glycerol (a by-product of biodiesel production). This process occurs through fractional vacuum distillation, the methanol recovery route in the deacidification process and the removal of methanol from the reaction medium. The separation stages of the crude glycerol implemented enabled a degree of purification of 99.77%, meeting the specifications of the pharmaceutical use. The developed model allowed for the optimization of the purification process, raising by 40% the mass flow rate of pure glycerol. A conclusion could be drawn that the use of crude glycerol is an excellent option for the development of new products with greater added-value, contributing to the zero waste principles and to the circular economy.

Crude Glycerol as a Potential Feedstock for Future Energy via Thermochemical Conversion Processes: A Review

Biodiesel is an emerging substitute for petroleum-based products. It is considered an ecologically safe and sustainable fuel. The high cost of biodiesel production is linearly related to its feedstock. Crude glycerol, which is a by-product of the biodiesel industry, is also a major challenge that must be addressed. A large volume of crude glycerol needs to be disposed of, and this involves processing, dumping, and land requirements. This increases the cost of biodiesel production. One way to decrease the cost of biodiesel production is to utilize its by-product to make valuable products. Crude glycerol can be processed to produce a variety of chemicals and products. The present utilization of crude glycerol is not enough to bring down its surplus availability. Thermochemical conversion processes can utilize crude glycerol as a starting feedstock and convert it into solid, liquid, and gaseous fuels. The utilization of crude glycerol through integrated thermochemical conversion processes could lead to an integrated biorefinery. This review paper highlights the research scope for areas where crude glycerol could be utilized as a feedstock or co-feedstock in thermochemical conversion technology. Various thermochemical conversion processes, namely, gasification, pyrolysis, combustion, catalytic steam reforming, liquefaction, and supercritical water reforming, are discussed and shown to be highly suitable for the use of crude glycerol as an economical feedstock. It is found that the integration of crude glycerol with other thermochemical conversion processes for energy production is a promising option to overcome the challenges related to biodiesel production costs. Hence, this paper provides all the necessary information on the present utilization status of crude glycerol in thermochemical conversion processes, as well as identifying possible research gaps that could be filled by future research studies.

Use of Crude Glycerol for Glycerolysis of Free Fatty Acids in Crude Palm Oil

The glycerolysis of crude palm oil (CPO) using potassium hydroxide was studied. This work aimed to evaluate free fatty acid (FFA) conversion in CPO through glycerolysis using crude glycerol. The effect of molar ratios of FFA to crude glycerol, rea

Simultaneous Lipid Production and Valorization of Crude Glycerol by Mixotrophic and Heterotrophic Cultivation of <em>Arthrospira platensis

This study investigates the possible use of crude glycerol as external carbon source for mixotrophic and heterotrophic cultivation of Arthrospira platensis for the purpose of producing lipid. Recently, biodiesel has become a remarkable biofuel while cyanobacterial lipid is an alternative feedstock for biodiesel production. In this study effect of carbon source concentration, trophic culture type on production of biomass, chlorophyll, protein, total carbohydrate and lipid were examined. In terms of total lipid content, the highest value was detected as 5.78 ± 0.21 mg/g cell with 10 mM crude glycerol in mixotrophic cultivation on 18th day. Higher specific growth rates were detected in mixotrophic cultures. The fatty acid composition was detected by gas chromatography. The produced lipid had the basic fatty acids for a quality biodiesel production — palmitic, stearic, oleic and linoleic acids. The biodiesel potential of produced lipid was investigated. The indicator of oxidative stability of the fuel, iodine value was in accordance with UNE-EN 14214. Cetane number and oxidative stability are related to productive combustion characteristics of fuel which comply with ASTM 6751 standards. These results show that the fatty acid composition of the produced lipid, from a waste material via economical fermentation, is suitable for a qualitative fuel production.

Two-Stage Anaerobic Codigestion of Crude Glycerol and Micro-Algal Biomass for Biohydrogen and Methane Production by Anaerobic Sludge Consortium

Optimization of factors affecting biohydrogen production from the codigestion of crude glycerol and microalgal biomass by anaerobic sludge consortium was conducted. The experiments were designed by a response surface methodology with central composite design. The factors affecting the production of hydrogen were the concentrations of crude glycerol, microalgal biomass, and inoculum. The maximum hydrogen production (655.1 mL-H2/L) was achieved with 13.83 g/L crude glycerol, 23.1 g-VS/L microalgal biomass, and 10.3% (v/v) inoculum. The hydrogenic effluents obtained under low, high, and optimal conditions were further used as substrates for methane production. Methane production rates and methane yield of 868.7 mL-CH4/L and 2.95 mL-CH4/L-h were attained with the effluent produced under optimum conditions. The use of crude glycerol and microalgal biomass as cosubstrates had an antagonistic effect on biohydrogen production and a synergistic effect on methane fermentation. The two-stage process provided a more attractive solution, with a total energy of 1.27 kJ/g-VSadded, than the one-stage process.

Using Glycerol to Produce European Sea Bass Feed With Oleaginous Microbial Biomass: Effects on Growth Performance, Filet Fatty Acid Profile, and FADS2 Gene Expression

Using a circular economy concept, the present study investigated the use of crude glycerol, a primary by-product of biodiesel production, as a low-priced nutrient source for heterotrophic cultivation of the fungus-like protist Schizochytrium limacinum SR21 strain. The whole biomass of this oleaginous microorganism, rich in docosahexaenoic acid (DHA) and high-quality proteins, was then paired with a vegetable oil (VO) source and used to replace fish oil (FO) in European sea bass (Dicentrarchus labrax) feeds. Four nutritionally balanced diets were formulated: diet FO (a FO-based diet), diet VO + 0 (a VO-based diet without S. limacinum), and diets VO + 5 and VO + 10 that were VO-based feeds supplemented with 5 and 10% of S. limacinum, respectively. After a 3-month feeding trial, fish of all dietary groups tripled their initial weight, but growth and feeding efficiencies of D. labrax were not significantly different among treatments. Although the formulated diets were balanced for polyunsaturated fatty acids (PUFAs), fish fed with feeds containing either VO or VO plus 5 and 10% of S. limacinum biomass had significantly higher levels of PUFAs in the flesh than fish fed the FO-based diet. Values of health-related lipid indexes, such as atherogenicity index, thrombogenicity index, and flesh lipid quality as well as n-6/n-3 and PUFAs/SFAs ratios confirmed the high nutritional value of sea bass filet, thus representing a healthy product for human consumption. Although the PUFAs/SFAs ratio showed a significantly higher value in fish fed with VO-based diets supplemented with S. limacinum than in those fed with FO diet, suggesting a better filet quality, the n-6/n-3 ratio clearly indicated that filet quality of dietary group FO was best (value of 0.55) and that of group VO + 10 second best (value of 0.98). We also evaluated the nutritional regulation of Δ6-desaturase (or fads2) gene expression in European sea bass liver. European sea bass fed the VO + 0 diet had the highest number of mRNA copies for Δ6-desaturase (or fads2), fish fed with diet VO + 10 the lowest. Our study adds to the growing body of literature concerning the use of thraustochytrid biomass as a valid alternative to marine-derived raw materials for European sea bass feeds.

Polyhydroxyalkanoates and pigments coproduction by Arthrospira (Spirulina) platensis cultivated in crude glycerol

Valorization of industrial waste as an alternative carbon source for microalgae mixotrophic cultivation and co-production of high-value compounds are strategies to enhance the bioprocess revenue and make large-scale production of microalgae polyhydroxyalkanoates (PHAs) feasible, with these biopolymers as potential substitutes to conventional polymers, such as polypropylene (PP) and high-density polyethylene (HDPE). In this sense, the use of crude glycerol, a main byproduct of the biodiesel industry, is an alternative to reduce cultivation costs and, at the same time, to provide a biotechnological solution for the excess of this byproduct produced, approximately 10 wt% per biodiesel batch. Thus, this work evaluated the effect of pure and crude glycerol supplementation and nutrient depletion (N and P) on growth, total carotenoids, phycocyanin and PHAs content in Arthrospira platensis xenic cultures. The highest final biomass concentrations, 1.68 and 1.40 g L-1, and PHAs contents, 1.1 and 0.5 % were achieved by supplying a Zarrouk medium with 6.14 g L-1 of pure or crude glycerol, respectively. In spite of having its content reduced at 6.14 g L-1 of pure glycerol, phycocyanin still presents a reasonable content (4.2 %) in this condition and in crude glycerol at 3.07 g.L-1 attained the highest content (10.8 %). On the other hand, glycerol mixotrophic cultivations with simultaneous nutrient depletion (nitrogen or phosphorus) did not improve the accumulation of PHAs.

Mixotrophic Growth of Astaxanthin-Rich Alga Haematococcus pluvialis using Refined Crude Glycerol as Carbon Substrate: Batch and Fed-Batch Cultivations

Due to a current overabundance of crude glycerol produced from the biodiesel industry, the compound has the potential to be used as an inexpensive carbon source for growing the green microalga Haematococcus pluvialis (H. pluvialis), the richest source of natural astaxanthin (ATX). In order to investigate the practical use of crude glycerol, microalgal cultures were grown mixotrophically and heterotrophically in BG11 medium with the supplementation of refined crude glycerol, a mixture of glycerol and ethanol, under 2, 5 and 7 g L-1, using photoautotrophic cultivation as a control. H. pluvialis green-stage growth and red-stage ATX accumulation were effectively facilitated by mixotrophic conditions, with the highest µ of 0.27 ± 0.03 day-1 and the highest ATX content of (3.5 ± 0.4 % wt) (both observed under 7 g glycerol L-1). In contrast, growth was completely inhibited under heterotrophic conditions. Under repeated fed-batch operation, the exponential growth phase, during green-stage mixotrophic cultivation, was significantly extended from 5 days (in batch) to 24 days, making biomass yield of 1.86 ± 0.06 g DCW L-1 (around 2.6-fold higher). Monitoring of substrates (glycerol, ethanol and nitrate) in the broth was carried out and subsequently suggested that further optimization of media could be made.

Assessing the use of crude glycerol from biodiesel production as an alternative to boost methane generation by anaerobic co-digestion of sewage sludge

In this work, the effect of the addition of crude glycerol (GL) (1 and 3% (v v−1)) from biodiesel production on anaerobic digestion of sewage primary sludge (PS), was evaluated through biochemical methane potential tests. Parameters such as pH, volatile acid/alkalinity ratio, chemical oxygen demand, volatile solids (VS) and carbon/nitrogen (C/N) ratio were monitored to assess process stability and performance. The methane yield from the co-digestion experiments of the binary mixture comprising PS and GL corresponded 223.8 mL CH4 g−1 VS and 368.8 mL CH4 g−1 VS for the tests supplemented with 1 and 3% GL, respectively, which represent an increase in methane yield of 61% and 167% compared to the control test conducted only with PS (138.2 mL CH4 g−1 VS). For each percentage increase in the applied VS load, the percentage increase in methane yield was found to be 4.7% and 5.7% for the tests with 1% and 3% glycerol, respectively. At the highest GL content, the maximum daily biogas generation rate was reached (i.e., 56.8 mL g−1 VS d−1). However, for this particular condition, an initial instability period with methanogenesis inhibition of 5.8 days was noticed, likely related to the accumulation of intermediate volatile acids. Overall, the results suggest that the use of crude glycerol as a co-substrate for the digestion of sewage sludge is interesting alternative to maximize the generation of biogas and methane, although its quantity should be controlled to avoid overload conditions which may compromise the stability of the system.

Investigation on the effect of ultrasonic-assisted transesterification for green synthesis of glycerol carbonate from crude glycerol

The present work demonstrates the utilization of ultrasonic-irradiation for synthesis of glycerol carbonate (GC) with direct use of crude glycerol (C.Gly) and dimethyl carbonate (DMC). This transesterification reaction was catalysed by calcium oxide (CaO) and the effect of ultrasonic-assisted transesterification reaction was studied. In order to verify the contents of C.Gly, the C.Gly obtained from biodiesel production plant was characterized and the results showed that C.Gly consists of 71.21%w/w glycerol, 16.01%w/w of moisture, 7.10%w/w of methanol, 2.76%w/w of ash, 3.60 %w/w of soap and 10.02%w/w of matter organic non-glycerol (MONG). Subsequently, effects of reaction temperature, reaction time, molar ratios of reactants and catalyst loading on C.Gly conversion and GC yield have been investigated. The highest yield of GC (95.41%) was attained with 9 mol% of CaO catalyst loading, 3:1 molar ratio of (DMC:C.Gly) at 70 °C for 90 min. The yield of GC was observed to rise with all the reaction parameters till the optimum conditions obtained. Moreover, the yield of GC obtained from ultrasonic-assisted was compared with the conventional-heating method done in the previous study. It was noticeable that the yield of GC obtained via ultrasonic-assisted was found to be 51.44% better than conventional-heating transesterification. In conclusion, the production of GC via ultrasonic-assisted transesterification shows better feasibility than that of the conventional-heating method.

Increase in biomass productivity and protein content of Spirulina sp. LEB 18 (Arthrospira) cultivated with crude glycerol

Glycerol is a byproduct of biodiesel production. Purified, this compound has several applications; however, in its crude form, its commercial value is limited. An alternative use of crude glycerol is its application as an organic carbon source in microalgal cultures. This study aimed to investigate the different concentrations in crude glycerol influence productivity, biomass concentration, and biomolecules content in cultures of Spirulina sp. LEB 18. Microalga was cultured in media supplemented with different glycerol concentrations in Erlenmeyer bioreactors during 15 days. The best glycerol concentration was 2.5 g L−1, which led to the maximum biomass productivity (0.43 g L day−1). Proteins were the largest component of the biomass (75.7% w w−1, 2.5 g L−1 glycerol) and could be used to obtain high-added-value compounds. Carbohydrates ranged from 7.0 (control) to 8.9% (1.5 g L−1) w w−1. Chlorophyll was reduced up to 47% (9.14 mg g−1) in the assay using 5 g L−1 of glycerol. The lipids produced in this condition (8.3% w w−1, 2.5 g L−1 glycerol) presented interesting properties for biodiesel production because of their high content of saturated fatty acids (260.56 mg g−1, 2.5 g L−1 glycerol). Microalgae culture with crude glycerol could aggregate value to a biodiesel co-product through biocompounds production making the biofuel production process more sustainable.

Use of Biofuel Industry Wastes as Alternative Nutrient Sources for DHA-Yielding Schizochytrium limacinum Production

The simultaneous use of crude glycerol and effluent from anaerobic digestate, both wastes derived from the biofuel industry, were tested in the frame of circular economy concept, as potential low-cost nutrient sources for the cultivation of rich in docosahexaenoic acid (DHA) oil microalgae strain Schizochytrium limacinum SR21. Initially, the optimal carbon and nitrogen concentration levels for high S. limacinum biomass and lipids production were determined, in a culture media containing conventional, high cost, organic nitrogen sources (yeast extract and peptone), micronutrients and crude glycerol at varying concentrations. Then, the effect of a culture media composed of crude glycerol (as carbon source) and effluent digestate at varying proportions on biomass productivity, lipid accumulation, proximate composition, carbon assimilation and fatty acid content were determined. It was shown that the biomass and total lipid content increased considerably with varying effluent concentrations reaching 49.2 g L−1 at 48% (v/v) of effluent concentration, while the lipid yield at the same effluent concentration reached 10.15 g L−1, compared to 17.0 g L−1 dry biomass and 10.2 g L−1 lipid yield when yeast extract and peptone medium with micronutrients was used. Compared to the control treatment, the above production was obtained with 48% less inorganic salts, which are needed for the preparation of the artificial sea water. It was shown that Schizochytrium limacinum SR21 was able to remediate 40% of the total organic carbon content of the biofuel wastes, while DHA productivity remained at low levels with saturated fatty acids comprising the main fraction of total fatty acid content. The results of the present study suggest that the simultaneous use of two waste streams from the biofuel industry can serve as potential nutrient sources for the growth of Schizochytrium limacinum SR21, replacing the high cost organic nutrients and up to one half the required artificial sea water salts, but upregulation of DHA productivity through optimization of the abiotic environment is necessary for industrial application, including aqua feed production.

Effect of utilization of crude glycerol as substrate on fatty acid composition of an oleaginous yeast Rhodotorula mucilagenosa IIPL32: Assessment of nutritional indices

This work studied the use of crude glycerol obtained from biodiesel industry as substrate to generate yeast lipid from Rhodotorula mucilagenosa IIPL32 MTCC 25056. Crude glycerol is a low value by product obtained from biodiesel industry. Rhodotorula mucilagenosa IIPL32 MTCC 25056 was evaluated for its potential to produce lipid using crude glycerol as sole source of carbon. Under nitrogen limiting condition a lipid and biomass content of 5.6 g/L and19.7 g/L were obtained from crude glycerol. The fatty acid profile was found to be interestingly rich in oleic acid (61.88%), linoleic acid (16.17%) and linolenic acid (1.03%) comprising ~80% of MUFA and PUFA of total lipid. Further, evaluations were attempted to compare MUFA rich yeast lipid against different plant-borne edible oils commonly used in India. In this study, nutritional indices were calculated to check feasibility of using yeast oil as a plausible blend to edible oil.