Low Oil Yield Research Articles

Expression of the heterologous Dunaliella tertiolecta fatty acyl-ACP thioesterase leads to increased lipid production in Chlamydomonas reinhardtii

Biofuel production from genetically-engineered microalgae is currently among the most widely studied strategies in generating renewable energy. However, microalgae currently suffer from low oil yields which limit the commercial feasibility of industrial-scale production. A major bottleneck in cost-efficient biofuel production from microalgae is the dilemma between biomass productivity and lipid accumulation. When grown under stressful culture conditions such as nitrogen depletion, microalgae accumulate large amounts of neutral lipids, but it comes at the expense of growth which negatively impacts overall lipid productivity. Overexpression of acyl-ACP thioesterases (TE) had been successful in increasing the production of fatty acids (FA) in prokaryotes such as E. coli and cyanobacteria, but has not been effectively tested in microalgae. In this study, we introduced a TE from D. tertiolecta (DtTE) into C. reinhardtii to investigate its effects on FA production without compromising growth. The results indicate that C. reinhardtii transformants were able to produce 63 and 94% more neutral lipids than the wild-type, which translates to an approximately 56% improvement in total lipids, without compromising growth. These findings demonstrate the cross-species functionality of TE, and provide a platform for further studies into using TE as a strategy to increase biofuel production from microalgae.

Soil quality assessment of different Camellia oleifera stands in mid-subtropical China

Camellia oleifera is a woody oil plant, which suffers from low yields in mid-subtropical areas of China. While increasing yields plays an important role in the development and security of the national edible oil industry, scientific evaluation of soil quality, which is essential for improving yields, has not yet been conducted for C. oleifera. To study soil quality and determine the factors limiting yields, 60 soil samples were collected from plantation stands producing different oil yields in mid-subtropical China. Thirty-two physical, chemical, and biological properties of soil were examined based on a one-way analysis of variance, canonical correspondence analysis (CCA) and principal component analysis (PCA). In addition, soil quality was assessed by the soil quality index (SQI) and grey relational analysis (GRA). Significantly high values were found for most properties in the high oil yield soil (HYS) samples, including soil organic matter (SOM), total nitrogen (TN), available calcium (ACa), available boron (AB), microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), bacteria, actinomycetes, total phosphatase (TOP), and urease. Conversely, available P (AP), available potassium (AK), and AB were depleted in the low oil yield soil (LYS) samples. Five soil indicators, namely SOM, AP, ACa, MBC, and catalase, were selected to establish a minimum data set. From this, soil quality was ranked as HYS>medium oil yield soil (MYS)>LYS, with SQI values of 0.65, 0.46, and 0.38, respectively. A similar trend was observed for the GRA results. A significant correlation (coefficient value of 0.699) was found between the SQI and oil yield. With higher SQI scores and a higher association degree, HYS had a greater nutrient supply and microbiological activity than MYS and LYS. SOM appeared to be the limiting factor for low oil yield, with deficiencies in AP found to be major constraints of yield in mid-subtropical China. Measures to improve the AB and AK content should also be considered in the study areas.

Paleoenvironmental reconstruction of the coal- and oil shale-bearing interval in the lower Cretaceous Muling Formation, Laoheishan Basin, northeast China

The Laoheishan Basin in northeast China has been filled with Lower Cretaceous coal- and “oil shale”-bearing sediments. The basin fill includes from base to top alluvial conglomerate (lower member of Muling Formation), fan delta sediments interbedded with coal and oil-prone mudstone (denominated as “oil shale”) layers in the upper member of Muling Formation, and volcaniclastic rocks (Dongshan Formation). In the present study, the maturity of organic matter, oil shale quality, and paleoenvironment of the coal and oil shale accumulation are investigated based on macro- and micropetrographic data, proximate and ultimate analyses, bulk geochemical parameters, biomarkers analysis and stable isotope geochemistry.In the Laoheishan Basin, both coal and “oil shale” layers are derived from land plant organic matter. This contrast the “oil shale” of this basin from oil shale/coal intercalations in fault-related basins, in which oil shale has been found to be of algal origin. The coal is sub-bituminous in rank, hydrogen-rich and oil-prone. The “oil shale” is of low-medium grade and the relatively low oil yield may relate to the abundant resinite and sporinite, because of their lower generation potential compared with alginite. Accumulation of the high-ash coal commenced in low-lying mire, drowned during frequent floodings. Subsequently high-ash, low-sulfur coal was deposited in a stable low-lying mire, under oxic conditions and limited bacterial activity. Afterwards the mire was drowned and formed a freshwater, dysoxic to oxic shallow lake, in which “oil shale” layers accumulated. Finally, the depositional environment returned to low-lying mire but probably with a brackish influence, as indicated by elevated sulfur contents in the uppermost samples. Petrography- and biomarker-based proxies indicate that gymnosperms dominated the paleovegetation of the mire, accompanied by variable amounts of herbaceous plants, such as ferns.

Optimization of Ultrasound Extraction of Cactus Pear(Opuntia ficus indica)Seed Oil Based on Antioxidant Activity and Evaluation of Its Antimicrobial Activity

The purpose of the present study was to determine the optimal ultrasound conditions (amplitude level and time) for the extraction of cactus pear seed oil with the highest antioxidant activity using a closed system. Seed oil was analyzed for yield, antioxidant activity by ABTS and DPPH, and antimicrobial activity. Conventional extraction methods were assessed for comparison. Amplitude level significantly affected antioxidant activity in linear terms (p< 0.0001 DPPH andp< 0.001 ABTS, resp.) so, at lower amplitudes, the higher antioxidant activity was achieved. The optimum ultrasound extraction conditions were of 78% amplitude for 10 min and yielded antioxidant activity values of 66.25 mg AAE/100 g and 289 µmol TE/100 g for ABTS and DPPH, respectively. Compared with conventional extraction methods, ultrasound exhibited lower oil yield and antioxidant activity but had the potential to achieve comparable results if multiple ultrasound extractions are performed in the time needed by conventional methods. Seed oils showed similar antimicrobial activity despite the extraction method and were more effective againstEscherichia coli. The results demonstrated that ultrasound can be an alternative extraction method of seed oils from fruits such as cactus pear.

Essential Oil Composition of Endemic Arabis purpurea Sm. & Arabis cypria Holmboe (Brassicaceae) from Cyprus.

There are very few reports on the phytochemistry of the Arabis L. (Brassicaceae) species in the literature. Here we present essential oil composition of aerial parts of two endemic Arabis species from Cyprus. The essential oils of Arabis purpurea Sm. and Arabis cypria Holmboe afforded very low oil yields (< 0.01% (v/w) yield). Sixty six compounds were identified in the essential oil of A. purpurea that represent 82.75 ± 0.21 % (n = 3) of the oil. The major components of the oil were nonacosane 16.18 ± 0.13 %, heptacosane 14.91 ± 0.17 %, hexahydrofarnesyl acetone 12.44 ± 0.10 % and phytol 7.36 ± 0.10 % (n = 3). Forty three compounds were identified in the essential oil of A. cypria which represent 81.28 ± 1.55 % (n = 3) of the oil. The major components of the oil were nonacosane 20.25 ± 0.47 %, heptacosane 9.13 ± 1.88 %, hexahydrofarnesyl acetone 9.03 ± 0.44 % and 1-tetradecanol 4.38 ± 2.60 % (n = 3). To the best of our knowledge this is the first report on the essential oil compositions of these species.

Ultrasound-Assisted Aqueous Enzymatic Extraction of Oil from Pomegranate Seeds

Pomegranate seed oil presents nutraceutical properties. Industrial processes for extraction of edible oils from seeds generally involve a solvent extraction step. Safety considerations on the use of organic solvents prompted attempts to develop aqueous extraction. However, aqueous extraction processes are usually characterized by low oil yields. The objective of this work was to overcome these low yields by using enzymes. The pomegranate seeds were treated with two enzymes—cellulase and Peclyve V. The extraction temperature, the time, the enzyme concentration, and the water/seeds ratio were varied between 35 and 55 °C, 2 and 8 h, 2 and 4 % w/w, and 2/1 and 6/1 mL/g, respectively. The optimum yield accomplished (15.33 g oil/100 g dry seeds at 2 h or 81 % oil recovery) was comparable to the yields obtained by other extraction methods, such as normal stirring, cold pressing, superheated fluid extraction, indirect ultrasound-assisted extraction and supercritical extraction, (4.29–25.11 g oil/100 g seeds) at similar or longer extraction times (10 min–72 h). In addition, this work studies the enhancement of aqueous enzymatic extraction of pomegranate seed oil by ultrasound probe. It was found that only 10 min in water are needed to recover oil with a yield of 18.15 g oil/100 g dry seeds, a value similar to or higher than those of the conventional procedures. Thus, the use of ultrasounds increased the yield of enzymatic extraction by 18.4 % and reduced the extraction time by 91.7 %.

Influence of Moisture Content and Seed Dimensions on Mechanical Oil Expression from African Oil Bean (Pentaclethra macrophylla Benth) Seed

Purpose: New low-cost oilseeds are needed to meet an ever-increasing demand for oil for food, pharmaceutical, and industrial applications. African oil bean seed is a tropical crop that is underutilized and has high oil yields, but there have been no studies conducted on its mechanical oil expression up to now. The objective of this work was to investigate the effect of moisture content and seed dimensions on mechanical oil expression from the seeds. Methods: Fresh oil bean seeds were procured, de-hulled, and cleaned. Initial seed moisture content, obtained in accordance with the ASAE standard, was 12% dry basis (db). The seeds were further conditioned by dehydration and rehydration prior to oil expression to obtain four other moisture levels of 8, 10, 14, and 16% db. The major diameter of the seeds was measured using digital vernier calipers, and the seeds were classified into size dimensions (< 40, 41-45, 46-50, 51-55, and > 55 mm). The oil yield and expression efficiency were obtained in accordance with standard evaluation methods. Results: The highest oil yield and expression efficiency (47.74% and 78.96%, respectively) were obtained for a moisture content of 8% db and seed dimensions of < 40 mm, while the lowest oil yield and expression efficiency (41.35% and 68.28%, respectively) were obtained for a moisture content of 14% db and seed dimensions between 51-55 mm. A mathematical model was developed to predict oil yield for known moisture content and seed dimensions, with a coefficient of determination <TEX>$R^2$</TEX> of 95% and the confidence level of the predictive model of 84.17%. The probability of prediction F ratio showed that moisture content influence was more significant than seed dimensions. Conclusions: The higher the moisture content and larger the seed dimensions, the lower the oil yield from African oil bean seeds.

Modeling and techno-economic analysis of shale-to-liquid and coal-to-liquid fuels processes

To alleviate the conflict between oil supply and demand, Chinese government has accelerated exploration and exploitation of alternative oil productions. STL (Shale-to-liquid) processes and CTL (coal-to-liquid) processes are promising choices to supply oil. However, few analyses have been made on their energy efficiency and economic performance. This paper conducts a detailed analysis of a STL process and a CTL process based on mathematical modeling and simulation.Analysis shows that low efficiency of the STL process is due to low oil yield of the Fushun-type retorting technology. For the CTL process, the utility system provides near to 34% energy consumption of the total. This is because that CTL technologies are in early development and no heat integration between units is implemented. Economic analysis reveals that the total capital investment of the CTL process is higher than that of the STL process. The production cost of the CTL process is right on the same level as that of the STL process.For better techno-economic performance, it is suggested to develop a new retorting technology of high oil yield for the STL process. The remaining retorting gas should be converted to hydrogen and then used for shale oil hydrogenation. For the CTL process, developing an appropriate heat network is an efficient way to apply heat integration. In addition, the CTL process is intended to be integrated with hydrogen rich gas to adjust H2/CO for better resource utilization.

Influence of canola seed dehulling on the oil recovery by cold pressing and supercritical CO2 extraction

Dehulling canola seeds provides an enriched cake in oil and proteins leading to an improved meal quality after oil extraction. The aim of this work was therefore to explore the impact of dehulling pre-treatment on both oil recovery and quality, using cold pressing followed by supercritical CO2 extraction. For this purpose, whole canola seeds, dehulled seeds, and reconstituted mixtures of 5% and 10% hulls were used to recover canola oil. After 1 h pressing, the obtained results showed that the lowest oil yield (≈37%) was obtained using dehulled seeds, indicating that dehulling adversely affects the efficiency of cold pressing. After pressing, remaining oil in press cake was extracted by supercritical CO2. After process optimization, the optimal parameters providing the maximum extraction yield (≈74%) were found at 40 °C temperature, 35 MPa pressure, 8.5 kg/h CO2 flow, and 10 min of conditioning. Using these conditions for grinded seeds, the combined process allowed a quasi-total oil recovery (95 ± 3%) and showed similar oil quantities extracted from either whole seeds, dehulled seeds, or reconstituted mixtures, demonstrating thus the efficiency of the proposed process. On the other hand, total phenolic compounds content in oil was reduced upon dehulling, and results show that the oil obtained by supercritical CO2 extraction was about twice enriched in phenolic compounds when compared to that obtained by mechanical pressing.

The extraction of β-Carotene from palm mesocarp via green sub-critical carbon dioxide

This study provides an explanation on experiments involving subcritical carbon dioxide extraction of palm oil from treated palm mesocarp to determine palm oil yield and the concentration of s-Carotene. As a comparison, Soxhlet extraction with six different solvents is posited as the conventional method. The overall oil yield is measured as the weight of oil per weight of sample, while anti-oxidant activity is determined by using 2,2-diphenyl-1-picryihydrazyl radical scavenging method. The sub-critical extraction is conducted at a constant temperature of 30°C and four different pressures at 10 MPa, 15 MPa, 20 MPa and 25 MPa. Results show that the sub-critical extraction may produce a higher concentration of s-Carotene than Soxhlet extraction, despite having a lower oil yield. Besides, the anti-oxidant analysis indicates a similar trend to the concentration of s-Carotene. Then, the best condition for a sub-critical extraction is found to occur at 25 MPa and 30°C.

The importance of ultrahigh pressure processing over the quality of the extracted oil from peony seeds (Paeonia suffruticosa Andr.)

The influence of extraction pressure on peony seeds (Paeonia suffruticosa Andr.) oil yield and quality was investigated using GC–MS, and the results indicated that the extraction of peony seeds oil under atmospheric pressure had the lowest oil yield and led to the absence of 9,12,15-octadecatrienoic acid in the oil. Ultrahigh pressure (UHP) of 350, 400, 450, 500 and 550MPa was used in this study and the analysis demonstrated that all the extracted peony seeds oils using UHP technology had the common compounds including hexadecanoic acid, 9,12-octadecadienoic acid, 9,12,15-octadecatrienoic acid, and octadecanoic acid, but their proportions in the extracted oils greatly differed. Although the oil yield was the highest, the extraction at a lower pressure of 350MPa achieved the greatest saturated fatty acids content of 49.49% and also the highest fatty acids number of 11, which might be due to the activated enzymes during the extraction. In contrast, the unsaturated fatty acids content in the extracted oil was up to be the highest of 87.57% when the extraction pressure of 500MPa was used, and its corresponding fat acidity was found to the lowest level of 3.5mg 100g−1 among all the extracted oils. This study suggests that the both oil yield and, in particular the oil quality are greatly sensitive to the extraction pressure.

Chemical composition and antibacterial activity of essential oil of Launaea lanifera Pau grown in Algerian arid steppes

ObjectiveTo evaluate the essential oil composition and the antibacterial activity of an Algerian endemic plant, Launaea lanifera Pau (L. lanifera), grown in arid steppe regions. MethodsL. lanifera essential oil was isolated from aerial parts by steam distillation and its chemical composition was evaluated by gas chromatography-flame ionization detector and gas chromatography with electron impact mass spectrometry. Furthermore, its in vitro antibacterial activity against four bacterial strains was tested following the agar disk diffusion method. ResultsThis species had a very low essential oil yield (0.005%). Twenty-four (92.6%) individual components were identified. The main constituents were hexahydrofarnesyl acetone (31.6%), (E)-β-ionone (8.5%), (E)-β-damascenone (7.0%), 2-methyltetradecane (3.8%), n-heptadecane (3.8%), limonene (2.8%) and β-caryophyllene (2.8%). No noteworthy antimicrobial activity was observed on the tested bacteria, neither Gram negative nor Gram positive. ConclusionsThis is the first report on the volatile constituents and antibacterial activity of L. lanifera. The studied essential oil does not possess significant activity against the tested microorganisms.

Optimisation of Oil Extraction Process from Australian Native Beauty Leaf Seed (Calophyllum Inophyllum)

Abstract In this study, the oil extraction process from Australian native beauty leaf seed has been optimised in terms of seed preparation and cracking, seed kernel treatment, moisture content and oil extraction methods. Two methods: mechanical oil extraction using an electric powered screw press and chemical oil extraction using n-hexane as an oil solvent have been applied to extract oil from the seed kernel. Both whole and grated kernels have been used for mechanical oil extraction process. The study indicated that treatment of seed kernel has a significant impact on oil yields for both techniques. It has been observed that kernels prepared to 15% moisture content provided the highest oil yields for both extraction methods. Mechanical extraction using the screw press could produce oil from the prepared kernels at a low cost. In addition, it has been obtained that oil yields by using grated kernels were relatively higher than the whole kernels. However, oil extraction by using this technique is ineffective due to relatively lower oil yields compared to chemical extraction. On the other hand, chemical extraction was found to be a very effective method for oil extraction because of its consistence performance and high oil yield, but cost of production was relatively higher due to high cost of solvent. The outcomes of this study are expected to serve as the basis on which industrial scale oil extraction can be made from beauty leaf seed.

Examination of molecular weight distributions of primary pyrolysis oils from three different oil shales via direct pyrolysis Field Ionization Spectrometry

The present study was focused on molecular weight and molecular weight distribution values of pyrolysis oils that could be useful in modeling oil shale thermochemical conversion processes, consistent with principles adopted in advanced coal pyrolysis modeling. Direct pyrolysis Field Ionization Spectrometry (py-FIMS) was applied to evaluate these parameters for volatilizing pyrolysis products with molecular weights greater than 50daltons. Stepwise heating, with an overall rate of 10°Cmin−1 up to 710°C, was used. The oil shales studied were Kukersite and Dictyonema oil shales from Estonia and Green River formation oil shale from the United States. Comparison of molecular distributions indicated a decreasing trend in molecular weight parameters (average molecular weight and width of the molecular weight distribution) of oils from higher oil yield oil shales to lower oil yield oil shales. In addition, the molecular weight trends seen among pyrolyzates from this study, under py-FIMS conditions, were compared to published values for pyrolyzates under other pyrolysis conditions and also to published values of the average molecular weight between cross-links for these three oil shales.

Pyrolysis in indirectly heated fixed bed with internals: The first application to oil shale

The indirectly heated fixed bed reactor with particularly designed internals has been devised to achieve advanced pyrolysis performance for coal (Energy & Fuels, 28, 2014: 236–244). This study extends the application of the reactor to oil shale and thereby solves the problems of low shale oil yield and low heating efficiency to shale particles in conventional fixed beds. The yield and quality of the produced shale oil and the rate heating the oil shale particles were compared for laboratory fixed beds without and with the particularly designed internals. It was shown that the use of internals doubled the efficiency of heating the oil shale inside the reactor from the heated reactor wall. Raising the heating temperature from 600°C to 1000°C increased the shale oil yield from 9.50% to 10.60% in the bed with internals, and reached 84.9% of the oil yield of Fischer assay (12.49wt.% in dry base). Furthermore, the shale oil maintained its relatively stable aliphatic hydrocarbon content. In the bed without any internals such a temperature rise sharply decreased the shale oil yield from 9.53% to 4.60%. Consequently, the fixed bed with internals would be an advanced reactor also for oil shale pyrolysis, which allows high process efficiency, high oil yield and high oil quality.

Quality Evaluation for Essential Oil of Cinnamomum verum Leaves at Different Growth Stages Based on GC–MS, FTIR and Microscopy

The essential oil yield and composition of the different growth stages of C. verum leaves were investigated. The results indicated that the density of the oil cells and the degree of oil accumulation were closely related to the essential oil yield. The leaves of the 2-year-old branches contained the highest density of oil cells (10.17 n/mm2), and the oils were largely accumulated, which coincided with the highest oil yield (5.81 %). The oils were less accumulated in leaves 1–4 collected from the annual branches and were mostly disintegrated in the leaves collected from the 4-year-old branches, resulting in lower oil yields (3.04 and 2.98 %, respectively). Eugenol was primarily found in the leaves collected from the 1-year- old branches, and the eugenol content decreased with the leaf growth. The results indicated clearly, that the leaves collected from the 1- and 2-year-old branches should be preferably chosen as the raw materials for the extraction of high-quality essential oils or eugenol. These results provide reference information for the rational utilization of cinnamon resources. Our research indicated that GC–MS and FTIR techniques, combined with microscopy, has been proved to be an effective strategy for assessment of essential oil quality for use in cinnamon plants.

Extraction of Spent Bleaching Earth in the Production of Renewable Diesel

AbstractThe extraction of oils based on animal fat and vegetable oil from two types of spent bleaching earths, namely from the acidic sepiolite and the nonacidic palygorskite, was investigated by the Soxhlet method with hexane as a solvent. The yields of oil were independent of the feedstock, whereas a much lower oil yield was obtained with palygorskite exhibiting also a smaller surface area as compared to sepiolite which provided a higher yield. The glyceride compositions were very similar in bleached and extracted oils, while slightly lower melting and crystallization energies were determined by differential scanning calorimetry for the extracted oils bleached with acidic clay indicating minor hydrolysis of triglycerides.

Essential Oil Composition of Centaurea stenolepis Kerner. from Turkey

:Essential oil composition of Centaurea stenolepis Kerner flowers and stems were investigated with GC, GC-MS. Flowers and stems of C. stenolepis had very low essential oil yield <0.01 % (v/w). Twenty eight compounds were identified in the flower oil which represent 53.5 % of the oil. Main components of the flower oil include caryophyllene oxide 12.6 %, hexadecanoic acid 10.6 % and β-Eudesmol 7.2 %. Forty compounds were identified in the stem oils which represent 74.2 % of the oil. Main components of the stem oils include hexadecanoic acid 38.4 % and phytol 12.9 %. Both flower and stem oils were rich on oxygenated sesquiterpene hydrocarbons and fatty acids.

Grain Quality of Medicinal Pumpkin (Cucurbita pepo subsp. Pepo var. styriaca) Affected by Type and Amount of Fertilizers

A field experiment was conducted at the Research Farm of Kurdistan University of Iran. Fourteen compositions of bio, organic and chemical fertilizers were done as treatments. Results showed that maximum seed (118.5 g.m-2) and fruit yield (6056.2 g.m-2) were obtained when pumpkin inoculated with nitrogen fixing and phosphate solubilizing bacteria + 50 % organic fertilizer. Maximum protein content (33.05 and 32.66 %) was obtained by inoculation of seeds with nitrogen fixing bacteria + 50 % chemical fertilizer and free-living nitrogen fixing bacteria + phosphate solubilizing bacteria + 50 % chemical fertilizer, respectively. The highest oil yield was obtained by a mixture of two biofertilizers + 50 % organic fertilizer (48.31 g.m-2) and the lowest oil yield (12.22 g.m-2) was resulted with control treatment.

Pilot-scale supercritical carbon dioxide extraction, physico-chemical properties and profile characterization of Moringa oleifera seed oil in comparison with conventional extraction methods

Moringa oleifera seed has gained importance over the years due to its great source of high quality oil that can be used in high value food, cosmetic, and pharmaceutical products. However, Moringa oil has never been successfully produced on the industrial basis due to the insufficient information available on the effective technique for oil extraction. It is generally extracted using organic solvent and screw pressing. Screw pressing generally produces low oil yield, on the other hand, the solvent extraction produces higher yield but its residue is the major health concern. This research proposed an alternative oil extraction from Moringa seeds using a pilot-scale supercritical fluid extraction (SFE) unit. SFE is considered as a green technology that is non-toxic and allows the elimination of polluting organic solvents. Carbon dioxide (CO2) was used as a solvent under near-critical and supercritical conditions in the pressure ranges from 15 to 35MPa and the temperature ranges from 25 to 35°C at the fixed flow rate of 20kg/h. The extractions made under higher pressure enhanced the oil yield. Extraction at highest pressure of 35MPa and moderate temperature of 30°C showed the most solvation power and extracted the maximum oil quantity of 75.27%. The oleic acid was the most abundant unsaturated fatty acid in Moringa oil amounted to 72.26–74.72%. At the lowest pressure (15MPa) CO2 was the most selective solvent for the extraction of oleic acid, tocopherols, and sterols. By comparison, the physico-chemical properties of oils extracted by supercritical CO2 were not substantially different from those of oils extracted by conventional methods. Overall, Moringa oil can be effectively extracted using a pilot-scale SFE at a relatively low temperature and pressure to give high quality oil.