Preparation of solid acid catalyst from glucose-starch mixture for biodiesel production

The aim of this work is to study the catalyst prepared by glucose-starch mixture. Assessment experiments showed that solid acid behaved the highest esterification activity when glucose and corn powder were mixed at ratio of 1:1, carbonized at 400 °C for 75 min and sulfonated with concentrated H₂SO₄ (98%) at 150 °C for 5 h. The catalyst was characterized by acid activity measurement, XPS, TEM and FT-IR. The results indicated that solid acid composed of CS_0.073O_0.541 has both Lewis acid sites and Broˇnsted acid sites caused by SO₃H and COOH. The conversions of oleic acid esterification and triolein transesterification are 96% and 60%, respectively. Catalyst for biodiesel production from waste cottonseed oil containing high free fatty acid (FFA 55.2 wt.%) afforded the methyl ester yield of about 90% after 12 h. The catalyst deactivated gradually after recycles usage, but it could be regenerated by H₂SO₄ treatment.     

Ethanesulfonic acid-based esterification of industrial acidic crude palm oil for biodiesel production

An industrial grade acidic crude palm oil (ACPO) pre-treatment process was carried out using ethanesulfonic acid (ESA) as a catalyst in the esterification reaction. ESA was used in different dosages to reduce free fatty acid (FFA) to a minimum level for the second stage of biodiesel production via alkaline transesterification reaction. Different process operating conditions were optimized such as ESA dosage (0.25-3.5% wt/wt), methanol to ACPO molar ratio (1:1-20:1), reaction temperature (40-70 °C), and reaction time (3-150 min). This study revealed the potential use of abundant quantities of ACPO from oil palm mills for biodiesel production. The lab scale results showed the effectiveness of the pre-treatment process using ESA catalyst. Three consecutive catalyst recycling runs were achieved without significant degradation in its performance. Second and third reuse runs needed more reaction time to achieve the target level of FFA content. Esterification and transesterification using ESA and KOH respectively is proposed for biodiesel industrial scale production. The produced biodiesel meets the international standards specifications for biodiesel fuel (EN 14214 and ASTM D6751).     

Production of algae-based biodiesel using the continuous catalytic Mcgyan® process

This study demonstrates the production of algal biodiesel from Dunaliella tertiolecta, Nannochloropsis oculata, wild freshwater microalgae, and macroalgae lipids using a highly efficient continuous catalytic process. The heterogeneous catalytic process uses supercritical methanol and porous titania microspheres in a fixed bed reactor to catalyze the simultaneous transesterification and esterification of triacylglycerides and free fatty acids, respectively, to fatty acid methyl esters (biodiesel). Triacylglycerides and free fatty acids were converted to alkyl esters with up to 85% efficiency as measured by 300 MHz ¹H NMR spectroscopy. The lipid composition of the different algae was studied gravimetrically and by gas chromatography. The analysis showed that even though total lipids comprised upwards of 19% of algal dry weight the saponifiable lipids, and resulting biodiesel, comprised only 1% of dry weight. Thus highlighting the need to determine the triacylglyceride and free fatty acid content when considering microalgae for biodiesel production.     

Lipase catalyzed methanolysis to produce biodiesel: Optimization of the biodiesel production

A lipase from Candida sp., suitable for transesterification of fats and oils to produce fatty acid methyl ester (FAME), was immobilized on a cheap cotton membrane, in this paper. The conversion ratio of salad oil to biodiesel could reach up to 96% with the optimal reaction conditions. Continuous reaction in a fixed bed reactor was also investigated. A three-step transesterification with methanol (methanolysis) of oil was conducted by using a series of nine columns packed with immobilized Candida sp. 99–125 lipase. As substrate of the first reaction step, plant or waste oil was used together with 1/3 molar equivalent of methanol against total fatty acids in the oil. Mixtures of the first- and second-step eluates and 1/3 molar equivalent of methanol were used for the second- and third-reaction steps. A hydrocyclone was used in order to on-line separate the by-product glycerol after every 1/3 molar equivalent of methanol was added. Petroleum ether was used as solvent (3/2, v/v of oil) and the pump was operated with a flow rate of 15 L/h giving an annual throughput of 100 t. The final conversion ratio of the FAME from plant oil and waste oil under the optimal condition was 90% and 92%, respectively. The life of the immobilized lipase was more than 10 days. This new technique has many strongpoints such as low pollution, environmentally friendly, and low energy costs.     

Lipase-catalyzed transesterification of rapeseed oils for biodiesel production with a novel organic solvent as the reaction medium

tert-Butanol, as a novel reaction medium, has been adopted for lipase-catalyzed transesterification of rapeseed oil for biodiesel production, with which both the negative effects caused by excessive methanol and by-product glycerol could be eliminated. Combined use of Lipozyme TL IM and Novozym 435 was proposed further to catalyze the methanolysis and the highest biodiesel yield of 95% could be achieved under the optimum conditions (tert-butanol/oil volume ratio 1:1; methanol/oil molar ratio 4:1; 3% Lipozyme TL IM and 1% Novozym 435 based on the oil weight; temperature 35 °C; 130 rpm, 12 h). There was no obvious loss in lipase activity even after being repeatedly used for 200 cycles with tert-butanol as the reaction medium. Furthermore, waste oil was also explored for biodiesel production and it has been found that lipase also showed good stability in this novel system.     

Effects of co-expression of molecular chaperones on heterologous soluble expression of the cold-active lipase Lip-948

The cold-active lipase gene Lip-948, cloned from Antarctic psychrotrophic bacterium Psychrobacter sp. G, was ligated into plasmid pColdI. The recombinant plasmid pColdI+Lip-948 was then transformed into Escherichia coli BL21. SDS-PAGE analysis showed that there was substantive expression of lipase LIP-948 in E. coli with a yield of about 39% of total protein, most of which was present in the inclusion body. The soluble protein LIP-948 only consisted of 1.7% of total LIP-948 with a specific activity of 66.51U/mg. Co-expression of molecular chaperones with the pColdI+Lip-948 were also carried out. The results showed that co-expression of different chaperones led to an increase or decrease in the formation of soluble LIP-948 in varying degrees. Co-expression of pColdI+Lip-948 with chaperone pTf16 and pGro7 decreased the amount of soluble LIP-948, while the soluble expression was enhanced when pColdI+Lip-948 was co-expressed with "chaperone team" plasmids (pKJE7, pG-Tf2, pG-KJE8), respectively. LIP-948 was most efficiently expressed in soluble form when it was co-expressed with pG-KJE8, which was up to 19.8% of intracellular soluble proteins and with a specific activity of 108.77U/mg. The soluble LIP-948 was purified with amylase affinity chromatography and its enzymatic characters were studied. The optimal temperature and pH of LIP-948 was 35°C and 8, respectively. The activity of LIP-948 dropped dramatically after incubation at 50°C for 15min and was enhanced by Sr(2+), Ca(2+). It preferentially hydrolyzed 4-nitrophenyl esters with the shorter carbon chain.     

Process engineering and optimization of glycerol separation in a packed-bed reactor for enzymatic biodiesel production

A process model for efficient glycerol separation during methanolysis in an enzymatic packed-bed reactor (PBR) was developed. A theoretical glycerol removal efficiency from the reaction mixture containing over 30% methyl esters was achieved at a high flow rate of 540 ml/h. To facilitate a stable operation of the PBR system, a batch reaction prior to continuous methanolysis was conducted using oils with different acid values and immobilized lipases pretreated with methyl esters. The reaction system successfully attained the methyl ester content of over 30% along with reduced viscosity and water content. Furthermore, to obtain a high methyl ester content above 96% continuously, long-term lipase stability was confirmed by operating a bench-scale PBR system for 550 h, in which the intermediates containing methyl esters and residual glycerides were fed into the enzyme-packed columns connected in series. Therefore, the developed process model is considered useful for industrial biodiesel production.     

Effect of moisture on lipase catalysed esterification of geraniol of palmarosa oil in non-aqueous system

Summary Optimisation of reaction conditions for the esterification of geraniol of palmarosa oil with n-butyric acid using immobilized lipase from Mucor miehei in non-aqueous system was carried out. Palmarosa oil could be easily esterified upto 95% w/w at 40°C in 24 h. Effect of moisture content was studied using Na₂SO₄ and recycling of the immobilized enzyme.     

Penicillium expansum lipase-catalyzed production of biodiesel in ionic liquids

Penicillium expansum lipase (PEL) was used to catalyze biodiesel production from corn oil in [BMIm][PF₆]¹ (an ionic liquid, IL) and tert-butanol. Both systems were optimized in terms of MeOH/oil molar ratio, reaction temperature, enzyme loading, solvent volume, and water content. The high conversion obtained in the IL (86%) as compared to that in tert-butanol (52%) demonstrates that the IL is a superior solvent for PEL-catalyzed biodiesel production. Poor yields were obtained in a series of hydrophilic ILs. Addition of salt hydrates affected biodiesel production predominantly through the specific ion (Hofmeister) effect. The impact of methanol on both activity and stability of PEL in the IL and in hexane was investigated, in comparison to the results obtained by two commonly used lipases, Novozym 435 and Lipozyme TLIM. The results substantiate that while different lipases show different resistance to methanol in different reaction systems, PEL is tolerant to methanol in both systems.     

Effect of water on lipase NS81006-catalyzed alcoholysis for biodiesel production

Biodiesel production catalyzed by free lipase has been drawing attention for its lower cost and faster reaction rate compared to immobilized lipase. It has been found that free lipase NS81006 could efficiently catalyze alkyl esters production and a certain amount of water is demonstrated to be necessary for the catalytic process. The effect of water content on liquid lipase NS81006-mediated methanolysis and ethanolysis for biodiesel production was first explored respectively in this paper. It was found that with water content ranging from 3% to 10% (based on oil weight), there was no significant difference in the final alkyl ester yield either in NS81006-mediated methanolysis or ethanolysis process, while the quality of biodiesel varied obviously. The acid value as well as the contents of monoglyceride and diglyceride were much lower in the lower water-containing system. With the water content decreasing from 10% to 3%, the acid value reduced from 8.24 to 4.89 mg KOH/g oil, and the content of MAG and DAG dropped to 0.31 and 0.22, from 0.62 and 0.74, respectively. Lipase could maintain rather good stability with proper alcohol adding strategy and the gradual reduction in biodiesel yield in the repeated uses resulted from the accumulation of by-product glycerol. The continuous running of lipase-mediated methanolysis of waste cooking oil was successfully realized at 30L reactor and a final methyl ester yield of over 90% could be obtained.     

Modeling the effect of mixing in biodiesel production

The transesterification reaction models available in the literature are valid only for one particular mixing condition. In this work, a modeling strategy is presented in order to predict the effect of mixing conditions in the transesterification process. The proposed methodology was applied to independent sets of experimental data available in the literature that show the dependency of the transesterification reaction on the frequency of rotation of the stirrer. The accuracy of the developed models corroborates the validity of the proposed modeling approach.     

渗透促进剂对紫草素透过大鼠腹部皮肤的作用

研究不同浓度的丙二醇、氮酮和油酸对紫草素透过大鼠腹部皮肤的影响．实验结果表明,不同浓度的丙二醇对紫草素经皮渗透均有促进渗透作用,丙二醇浓度为10％时促渗效果最佳,油酸也具有促进紫草素的经皮渗透作用,但是在本实验中氮酮抑制紫草素的经皮渗透。     

Experimental study of the spray characteristics of biodiesel based on inedible oil

We studied the spray characteristics of inedible oil using experimental and simulation methods. Spray penetration, spray cone angle and spray tip speed were measured at different biodiesel ratios in a constant volume vessel with wide visualization and high back pressure, using a high-speed camera. The characteristics of biodiesel spray were simulated under the same conditions using Star-CD software. The experimental results showed that, as the ratio of biodiesel in the blends increased, spray penetration and spray speed increased, but the spray cone angle decreased. Throughout the spray injection period, the region at 0.05–0.475S (spray tip penetration) was a key area affecting spray cone angle. From 0.8 ms after injection, the spray penetration deviation ratios started to increase with increasing biodiesel blend ratios. Simulation results showed similar macroscopic spray characteristics to the experimental results for jatropha oil. The results also showed that the Sauter mean diameter of blend fuels was greater than that of diesel, and spray was more concentrated, due to the higher viscosity and surface tension of the biodiesel, compared with conventional diesel fuel. The macroscopic and microscopic spray properties of blended fuels containing 5%, 10% and 20% biodiesel were similar to diesel.     

A comparison of lipase-catalyzed ester hydrolysis in reverse micelles, organic solvents, and biphasic systems

The performance of lipases from Candida rugosa and wheat germ have been investigated in three reaction media using three acetate hydrolyses as model reactions (ethyl acetate, allyl acetate, and prenyl acetate). The effect of substrate properties and water content were studied for each system (organic solvent, biphasic system, and reverse micelles). Not unexpectedly, the effect of water content is distinct for each system, and the optimal water content for enzyme activity is not always the same as that for productivity. A theoretical model has been used to simulate and predict enzyme performance in reverse micelles, and a proposed partitioning model for biphasic systems agrees well with experimental results. While the highest activities observed were in the micellar system, productivity in microemulsions is limited by low enzyme concentrations. Biphasic systems, however, support relatively good activity and productivity. The addition of water to dry organic solvents, combined with the dispersion of lyophilized enzyme powders in the solvent, resulted in significant enzyme aggregation, which not surprisingly limits the applicability of the "anhydrous" enzyme suspension approach. (c) 1995 John Wiley & Sons, Inc.     

Kinetic studies on the Rhizomucor miehei lipase catalyzed esterification reaction of oleic acid with 1-butanol in a biphasic system

The kinetics of the esterification of oleic acid with 1-butanol catalyzed by free Rhizomucor miehei lipase in a biphasic system was studied in a batch reactor. The reaction appeared to proceed via a Ping Pong bi–bi mechanism with 1-butanol inhibition. The kinetic constants of the model were determined from experiments at 30 °C with initial concentrations of oleic acid and 1-butanol in the organic phase and 0.05–0.2 g L⁻¹ enzyme in the aqueous phase. The model was used to simulate the batch concentration profiles of the product as well as the initial reaction rates. Agreement of the model with both the batch concentration profiles (average error of 7.2%) and the initial reaction rate per experiment (average error of 16.0%) was good.     

Enzymatic conversion of sunflower oil to biodiesel in a solvent-free system: Process optimization and the immobilized system stability

The feasibility of using the commercial immobilized lipase from Candida antarctica (Novozyme 435) to synthesize biodiesel from sunflower oil in a solvent-free system has been proved. Using methanol as an acyl acceptor and the response surface methodology as an optimization technique, the optimal conditions for the transesterification has been found to be: 45 ^oC, 3% of enzyme based on oil weight, 3:1 methanol to oil molar ratio and with no added water in the system. Under these conditions, >99% of oil conversion to fatty acid methyl ester (FAME) has been achieved after 50 h of reaction, but the activity of the immobilized lipase decreased markedly over the course of repeated runs. In order to improve the enzyme stability, several alternative acyl acceptors have been tested for biodiesel production under solvent-free conditions. The use of methyl acetate seems to be of great interest, resulting in high FAME yield (95.65%) and increasing the half-life of the immobilized lipase by about 20.1 times as compared to methanol. The reaction has also been verified in the industrially feasible reaction system including both a batch stirred tank reactor and a packed bed reactor. Although satisfactory performance in the batch stirred tank reactor has been achieved, the kinetics in a packed bed reactor system seems to have a slightly better profile (93.6 ± 3.75% FAME yield after 8–10 h), corresponding to the volumetric productivity of 48.5 g/(dm³ h). The packed bed reactor has operated for up to 72 h with almost no loss in productivity, implying that the proposed process and the immobilized system could provide a promising solution for the biodiesel synthesis at the industrial scale.     

Study on factors influencing stability of whole cell during biodiesel production in solvent-free and tert-butanol system

Utilizing whole cell biocatalyst for biodiesel production has some advantages since it can avoid the complex procedures of isolation, purification and immobilization of extracellular lipase. However, during repeated use of Rhizopus oryzae (R. oryzae) IFO4697 whole cell for biodiesel production in solvent-free system, the whole cell exhibited very poor stability; while the whole cell stability has been found to be significantly improved in tert-butanol system compared to that in solvent-free system. The difference in whole cell stability was found to be due to the difference of product accumulation between solvent-free and tert-butanol system. After 144 h reaction, glycerol and methyl ester accumulated in the cell in solvent-free system came up to about 1000 mg/g and 350 mg/g dry biomass, respectively, while in tert-butanol system, glycerol and methyl ester accumulation was kept at a relatively low level, approximately 100 mg/g and 2 mg/g dry biomass, respectively. The accumulated glycerol influenced whole cell stability through mass transfer limitation only, while the accumulated methyl ester influenced whole cell stability through both mass transfer limitation and product inhibition. Further study showed that a slight loss in enzymatic activity in tert-butanol system was caused by protein leakage.     

Effect of several factors on the mechanical properties of pressure-sensitive adhesives used in transdermal therapeutic systems

The effects of coating thickness, type of adhesive, and type and concentration of enhancer on the mechanical properties of two acrylic pressure-sensitive adhesives (PSAs) were investigated using a 2(4) factorial design and an optimization technique. Sixteen formulations containing 0% or 10% of either caprylic acid or methyl laurate in two different PSAs, namely Duro-Tak 87-2196 and Duro-Tak 87-2097, were prepared. The adhesive properties of these laminates were evaluated by applying the 90 degrees Dynamic Adhesive Strength Peel Test (90 degrees DASPT) and 1800 Release Liner Peel Test (180 degrees RLPT). Coating thickness, concentration of enhancer, and type of adhesive did affect the 90 degrees DASPT. For the 180 degrees RLPT, the most significant factors were coating thickness and concentration of enhancer, with a strong interaction observed between the two. Coating thickness and concentration of enhancer were also used to create mathematical models that correlated these factors with the mechanical properties of the PSAs. For this purpose, the optimization technique 3(2) was applied. It was found that the correlation of the above factors can be adequately described with polynomial equations, which can be used for predicting the mechanical properties of the laminates containing the above PSAs and methyl laurate (0%-10%).     

Effect of oleic acid on vegetative growth of the aphid-pathogenic fungus Erynia neoaphidis

Abstract The aphid-pathogenic fungus Erynia neophidis grew on a semi-defined medium containing 16 g·1⁻¹ glucose, 3 g·1⁻¹ yeast extract and 5 g·1⁻ mycological peptone only when the medium was supplemented with low concentrations of certain fatty acids. Of these, oleic acid fulfilled the growth requirement at a concentration of 0.02% (v/v), but higher concentrations were toxic, causing complete loss of viability of cultures at a concentration of 0.2% (v/v) in liquid medium and at 4% (v/v) on solid medium. The reduced viability of the fungus in liquid culture compared to that on equivalent solid medium, and at low inoculum density compared to high inoculum density in liquid medium, is explicable in terms of this toxicity.     

间歇及连续式固定化酶反应生产生物柴油

探讨了利用本实验室自制的Candida sp99．125脂肪酶转酯化合成生物柴油的过程。在利用间歇式反应得到最佳反应条件的情况下利用固定床反应器生产生物柴油,经过初步优化的试验结果表明,在采用分级流加甲醇下,生物柴油的转化率可以达到93％左右,并且固定化酶的使用寿命超过480h。