Improving Waste Cooking Oil Quality for Biodiesel Production with the Ethanolic By-product of Soybean Oil Extraction

Waste cooking oils (WCO) can be used as feedstock for biodiesel (fatty acid ethyl or methyl esters—FAEE or FAME) production. Their usual high acidity, high moisture, and low stability can impair the reaction yield and generate a low-quality biodiesel. Here, we performed liquid–liquid washings using WCO and ethanol-based solvents with the goal of generating oil-rich miscella as FAEE feedstocks with a higher quality than WCO. Three different solvents were evaluated: 99% ethanol, 95% ethanol, and the soybean oil extraction ethanolic phase (SEP), a by-product with immense unexplored antioxidant potential obtained by extracting soybean oil using ethanol. Washings were performed in a 1000 mL flat-bottom flask at 78.1 °C, using a 1:2 (w/v) oil/solvent ratio, under magnetic stirring (1200 rpm) for 10 min. Ethyl esters were prepared via homogeneous alkali transesterification using WCO and oil-rich miscella as feedstocks. Treatments reduced the acid value by 40–61% and the peroxide value by 15–50%. Improvements in feedstock quality generated 24–54% higher biodiesel yields. The oil-rich phase produced with SEP was 15% more resistant to oxidation than WCO. This was attributed to the transference of isoflavones from the SEP. However, biodiesel from treated samples presented equal or lower oxidative stability than FAEE from WCO. High-performance liquid chromatography (HPLC) analysis showed that no isoflavones remained in biodiesel after purification. Pretreatment of WCO with ethanol-based extracts such as the SEP has great potential to improve WCO quality for biodiesel production as it can be a source of plant-based antioxidants.     

Hydroperoxide as a Prooxidant in the Oxidative Stability of Soybean Oil

Fifteen milliliters of soybean oil having peroxide value (PV) of 0, 2, 4, 6, 8, or 10 meq/kg oil in a 35 mL serum bottle was sealed air-tight with a Teflon rubber septum and aluminum cap and was stored in a forced-air oven at 50 °C. The oxidative stability of soybean oil was evaluated daily for six days by measuring the headspace oxygen content and volatile compounds in the headspace of a sample bottle by gas chromatography. As the initial PV of the oil increased from 0 to 2, 4, 6, 8 and 10, the headspace oxygen decreased and the volatile compounds increased at p < 0.05. Hydroperoxide accelerated the oxidation of soybean oil. The correlation coefficient (R ²) between the headspace oxygen and the volatile compounds was 0.95. The increase of tertiary butyl hydroquinone (TBHQ) from 0 to 50 ppm for the oil of PV 4 or 8 had a significant effect on the oxidative stability at p < 0.05. The increase from 50 to 100 ppm for the oil of PV 4 or 8 did not significantly increase the stability at p > 0.05. The oxidative stability of PV 8 meq/kg and 50 ppm TBHQ was better than the control with PV 0 and 0 ppm TBHQ at p < 0.05. TBHQ was an effective antioxidant to improve the oxidative stability of soybean oil.     

Inulin as a Promising Alternative Feedstock for Docosahexaenoic Acid Production by Schizochytrium sp. ATCC 20888

Schizochytrium sp. is considered as a promising alternative commercial source of docosahexaenoic acid (DHA), but the production is hindered by the high feedstock cost. In this study, inulin is used as a cheap and readily available feedstock for Schizochytrium sp. ATCC 20888 to produce DHA. The strain could not utilize inulin directly and therefore inulin first needed to be hydrolyzed. Compared with the acidic hydrolyzate by HCl and hydrolyzate by endo‐inulinase, the hydrolyzate by exo‐inulinase serves as the most effective carbon source for microalgal growth. Hydrolysis of inulin by exo‐inulinase is further optimized, and up to 97.8% of inulin conversion is obtained under the optimal conditions of 40 °C, pH 7.0, substrate concentration of 80 g L^?1 and exo‐inulinase loading of 2 g kg^?1 substrate for 12 h. The resulting hydrolyzate containing mainly fructose is used for the DHA production by the microalga. The lipid content in biomass, DHA content in total fatty acids, DHA yield, and DHA productivity at 72 h reach 45.26%, 35.59%, 5.64 g L^?1 and 1.88 g L^?1 d^?1, respectively. The results suggest that inulin is an excellent feedstock for Schizochytrium sp. suitable for commercial DHA production. Practical Applications: DHA is an essential nutrient for human health and is widely used in infant formula and functional food. As a reserve carbohydrate, inulin present in plants represents a cheap, abundant, and readily available bioresource. This study describes the suitability of inulin as a promising alternative to glucose for DHA production by Schizochytrium sp. Hence, a practical bioprocess for commercial DHA production from inulin by Schizochytrium sp. could be developed. As far as it is known, this is the first report of inulin as a feedstock for Schizochytrium sp. to produce DHA.     

Oxidative Stability of Papaya Seed Oil From Hainan/Eksotika Obtained by Subcritical and Supercritical Carbon Dioxide Extraction

Papaya seed is a good source of edible oil with considerable antioxidant activity. Here, papaya seed oil (PSO) of Hainan/Eksotika variety was obtained by subcritical butane extraction (SBE) and supercritical carbon dioxide extraction (SCDE), and its yields, physicochemical properties, oxidative and thermal stability, and chemical and microscopic structures were compared. The results showed that SBE‐PSO had a higher yield (25.88 ± 0.29% vs. 19.47 ± 0.92%), but a lower melting point compared to SCDE‐PSO. Molecular structures indicated that there was no oxidative degradation during SBE and SCDE. Both SBE and SCDE caused significant structural changes of seed tissues. In addition, aldehyde composition analysis using high performance liquid chromatography (HPLC) showed that SBE‐PSO had fewer octanal, nonanal, 2‐decenal, and 2‐undecenal contents than SCDE‐PSO. All these results proved that SBE‐PSO exhibited superiority on the oxidative stability compared to SCDE‐PSO. It indicated that SBE was a superior method to obtain antioxidant edible oil with good stability.     

Content of Antioxidants,Antioxidant Capacity and Oxidative Stability of Grape Seed Oil Obtained by Ultra Sound Assisted Extraction

The goal of this work was to investigate the relationship between antioxidants’ content and the oxidative stabilities of grape seed oils obtained from the Cabernet Sauvignon variety. The samples of grape seed oils were obtained by ultrasound assisted extraction. The time of extraction was varied, while the other relevant parameters: extraction temperature, solvent to solid ratio and sonication power were kept constant. For the sake of comparison, the extraction was also done using the conventional Soxhlet method. For all the oil samples obtained, the contents of total phenolic compounds (TPC), α-tocopherol and fatty acids were determined using relevant analytic methods. Importantly, in the present study, the modern analytical techniques for estimation of antioxidant capacity (measuring the chemiluminescence intensity of a luminol-hemin solution) and oxidative stability [differential scanning calorimetry (DSC), coupled with thermogravimetry (TG)] were proposed. The obtained results prove that ultrasonic irradiation enables effective extraction of grape seed oil. It was shown that the extractive yields and the amounts of total phenolic compounds and α-tocopherol increase with time of extraction; the optimum time was determined. Results obtained in this work show that, for both oxidative stability and antioxidant capacity, TPC have a more important role then α-tocopherol.     

Catalytic Conversions in Aqueous Media. Part 2. A Novel and Highly Efficient Biphasic Hydrogenation of Renewable Methyl Esters of Linseed and Sunflower Oils to High Quality Biodiesel Employing Rh/TPPTS Complexes

An unusual high catalytic activity (TOF = 117,000 h⁻¹) and high catalyst productivity (TON = 9,700) have been achieved in the first example of partial hydrogenation of renewable polyunsaturated crude methyl esters of linseed and sunflower oils catalyzed by water soluble Rh/TPPTS complexes [TPPTS = P(C₆H₄-m-SO₃Na)₃] in aqueous/organic two-phase systems to afford monounsaturated fatty esters which is biodiesel first generation of improved oxidative stability, energy and environmental performance at a low pour point. This exceptionally high catalytic activity contrast with the general perception that industrially applied water soluble Rh/TPPTS catalysts normally exhibit very low rates in the conversions of higher molecular weight starting materials in aqueous/organic two-phase systems. For part 1 of this series see Ref. [14].     

A Novel Method of Endotoxins Removal from Chitosan Hydrogel as a Potential Bioink Component Obtained by CO2 Saturation

The article presents a new approach in the purification of chitosan (CS) hydrogel in order to remove a significant amount of endotoxins without changing its molecular weight and viscosity. Two variants of the method used to purify CS hydrogels from endotoxins were investigated using the PyroGene rFC Enzymatic Cascade assay kit. The effect of the CS purification method was assessed in terms of changes in the dynamic viscosity of its hydrogels, the molecular weight of the polymer, microbiological purity after refrigerated storage and cytotoxicity against L929 cells based on the ISO 10993-5:2009(E) standard. The proposed purification method 1 (M1) allows for the removal of significant amounts of endotoxins: 87.9–97.6% in relation to their initial concentration in the CS hydrogel without affecting the solution viscosity. Moreover, the final solutions were sterile and microbiologically stable during storage. The M1 purification method did not change the morphology of the L929 cells.