Optimization of variables affecting the direct transesterification of wet biomass from Nannochloropsis oceanica using ionic liquid as a co-solvent

Microalgae are a promising alternative source of several bioactive compounds useful for human applications. However, lipids are traditionally extracted with toxic organic solvents (e.g. mixture of chloroform and methanol or hexane). In this work, we developed a new lipid extraction protocol to obtain a fatty acids rich extract from the diatom Phaeodactylum tricornutum. Deep Eutectic Solvents (DES) and microwaves (MW) were investigated as pre-treatments for environmentally friendly solvent extractions using dimethyl carbonate (DMC) and supercritical CO2 (scCO2). Pre-treatments with various DES formed by choline chloride (ChCl) and different hydrogen bond donors (oxalic acid, levulinic acid, urea, ethylene glycol and sorbitol) were tested in combination with DMC extraction. DES formed by ChCl and carboxylic acids gave best results, increasing both selectivity and total fatty acids (TFA) extraction yield of DMC (respectively by 16% and 80%). DES combined with MW heating followed by DMC extraction allows to reach comparable TFA yield and fatty acid profile to traditional Bligh & Dyer extraction method and much better selectivity (88% vs. 35%). This pre-treatment was also demonstrated to improve significantly extraction efficiency of scCO2, increasing by 20 times TFA yield and providing highly purified triglycerides extracts.

Section: Introductionmentioning

confidence: 99%

Enhanced and Selective Lipid Extraction from the Microalga P. tricornutum by Dimethyl Carbonate and Supercritical CO₂ Using Deep Eutectic Solvents and Microwaves as Pretreatment

Tommasi

Cravotto

Galletti

et al. 2017

“…As presented in Figure , the biodiesel yields of [Bmim] 2 [HPO 4 ]-catalyzed IST of wet algae increase with the increasing amounts of methanol initially, while a slight decrease is observed when the amount of methanol is higher than 20 g. In contrast to the fluctuation of biodiesel yields of [Bmim] 2 [HPO 4 ]-catalyzed IST of wet algae under different methanol conditions, there is a continuous decrease of biodiesel yields of [Bmim][H 2 PO 4 ]-catalyzed IST of wet algae from 11.74% to 8.94%. Comparing with previous studies recognized in Table , the biodiesel yields of BAILs-catalyzed IST are comparative to traditional acid-catalyzed IST of wet algae with the high reusability of BAILs. ,, Similarly, the variation of biodiesel yields of [Bmim][HSO 4 ]-catalyzed IST of wet algae is consistent with the variation of amounts of cellulose extracted by [Bmim][HSO 4 ], which can be observed from their continuous increase from 9.34% to 11.76%. Obviously, there is a dual rule of BAILs in in situ transesterification of wet algae due to their deprotonation and H-bonding formation properties.…”

Section: Results and Discussionmentioning

confidence: 99%

“…In addition, the electron density at the bond critical point (BCP) and the core− valence bifurcation (CVB 1, the biodiesel yields of BAILs-catalyzed IST are comparative to traditional acid-catalyzed IST of wet algae with the high reusability of BAILs. 10,34,35 Similarly, the variation of biodiesel yields of [Bmim][HSO 4 ]-catalyzed IST increase from 8.79%, 3.67% to 11.25%, 7.12%, respectively, when 60% water content is added. The positions and strengths of the H-bonding of H 2 O-BAILs are varied with the structures of the ionic liquids to form stable geometries, which subsequently lead to the variation of the H-bonding interaction of BAILs-cellulose complexes.…”

Section: Acs Sustainablementioning

confidence: 99%

Effect of H-Bonding on Brønsted Acid Ionic Liquids Catalyzed In Situ Transesterification of Wet Algae

Shen

et al. 2020

Brønsted acid ionic liquids (BAILs) are effective to biodiesel production of in situ transesterification of wet algae due to their dual role as both solvents of cellulose and catalysts of transesterification. The cellulose solubilities of BAILs are depending on H-bonding of BAILs-cellulose in varied solvent conditions, which subsequently affect the biodiesel productions. For this reason, the effects of H-bonding between BAILs includingand cellulose under different methanol and water conditions on cellulose extractions are experimentally and theoretically investigated. The cellulose extractions in BAILs are decreasing as [Bmim][H 2 PO 4 ] > [Bmim] 2 [HPO 4 ] > [Bmim][HSO 4 ], contrary to the variation of their thermal stabilities and crystallinities caused by varied Hbonding of BAILs-cellulose. Increasing methanol is positive to cellulose extractions in [Bmim][HSO 4 ], while negative to those in [Bmim][H 2 PO 4 ] and [Bmim] 2 [HPO 4 ], due to the solvent effect of methanol confirmed by cyclic voltammetry (CV) measurements. The effect of water on H-bonding of BAILs-cellobiose is contrary to the effect of methanol. It is confirmed via the bonding interaction of BAILs-cellobiose through the density functional theory (DFT) computational method. However, the biodiesel yields are varied differently due to the competition of H-bonding of BAILs-cellobiose and deprotonation of BAILs under different methanol and water conditions. This study might pave the way to neutralize the negative effect of water on in situ transesterification via enhancing the cellulose extractions of BAILs.

“…Preliminary screening showed that acid catalysts (H 2 SO 4 and acetic acid) required much longer reaction times (>18h), which has been reported elsewhere. 24 Interestingly, when H 2 SO 4 was used in the presence and absence of the ionic liquid (1:10 weight ratio yeast:IL, 50 °C, 11.9 g methanol/g yeast, and 25% water content), the ionic liquid was found to reduce the overall FAME yield (13.6% vs 5.5%). Therefore, their study was discontinued in order to develop a faster process based on an alkaline catalyst.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Direct Conversion of the Oleaginous YeastRhodosporidium diobovatumto Biodiesel Using the Ionic Liquid [C₂mim][EtSO₄]

Ward

Munch

Çiçek

et al. 2017

In this study, the direct conversion of wet oleaginous yeast biomass to fatty acid methyl esters (FAME) using base transesterification in the presence of an ionic liquid was optimized. The ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate, was used to facilitate this process and improved the yields of FAME transesterified directly from wet biomass using potassium hydroxide (KOH) as a catalyst. Factorial screening was first used to identify critical factors affecting the transesterification yield, and subsequently, response surface methodology was employed to study the interaction of methanol, KOH, and temperature on reaction yield. The optimized conditions for dried biomass were found to be 16.9 g methanol/g yeast, 0.056 g KOH/g yeast, 2 g [C2mim[EtSO4]/g yeast, and 65 °C, which yielded 97.1% conversion of the maximum FAME yield in only 2.5 h. The optimized system was further studied to observe the reaction profiles and FAME yield over time from both dry yeast and fresh wet yeast biomass containing varying degrees of water (from 65 to 80 wt %). The ionic liquid was found to improve total overall yield of FAME (96.9 ± 0.4%) compared to the negative control without ionic liquid (69.6 ± 5.0%) when wet yeast was used. While all the ionic liquid was recovered from the reaction, it contained only 59.3% of the catalyst, suggesting a heterogeneous catalyst may be more appropriate in future work.