生物柴油研究进展

生物柴油作为一种可再生、生物可降解和无毒燃料引起了人们极大的关注，它可以通过动植物油的转酯反应来制备。综述了直接掺和、微乳化和热裂解制备生物柴油的方法，着重强调了目前国内外学者广泛采用的转酯法，即三甘油酯在酸、碱或酶等催化剂作用下经转酯反应制备生物柴油的研究进展。     

利用生物柴油副产物粗甘油发酵生产EPA

实验利用生物柴油副产物甘油为碳源,培养畸雌腐霉(Pythiumirregulare)发酵生产EPA。实验中所用废甘油为利用碱法催化大豆油与甲醇进行酯交换反应生成,粗甘油经过纯化精制作为碳源。EPA产量采用气相色谱分析,分析之前采用浓硫酸-甲醇酯化法进行脂肪酸甲酯化。由实验得出,最佳发酵条件为:温度为25℃,pH为6,转速为170r/min,粗甘油加入量为70g/L,此条件下获得的EPA产量为:105mg/L。     

Catalytic properties of a lipase from Photobacterium lipolyticum for biodiesel production containing a high methanol concentration

Biodiesel, an alternative fuel, is generated via the transesterification reaction of vegetable oil or animal oil with alcohol. Currently, many reports have noted that microbial lipases might be utilized for the production of biodiesel. Among them, immobilized Candida antarctica lipase B (Novozym435) is frequently utilized for its biocatalytic efficiency and availability. However, as the enzyme is unstable in a medium containing high concentrations of methanol, a multi-stepwise methanol supply is required for the efficient production of biodiesel. Photobacterium lipolyticum lipase (M37) was determined to be quite stable in a medium containing a high concentration of methanol. The enzyme activity was maintained for longer than 48 h without any loss at a methanol concentration of 10%. In an effort to evaluate enzyme performance in the production of biodiesel, we have compared M37 lipase and Novozym435 in the biodiesel production reaction using fresh or waste oil and methanol. In the 3-stepwise methanol feeding method generally conducted for Novozym435 in biodiesel production, the M37 lipase showed a similar or superior conversion yield to Novozym435. However, the M37 lipase evidenced significantly higher conversion yields in the 2 and 1 step methanol feeding reactions. Particularly in the 1 step process using 10% of methanol where almost no conversion was detected by Novozym435, the biodiesel yield achieved with M37 lipase reached a level of up to 70% of the possible maximum yield. Consequently, this methanol-tolerant lipase, M37, has been shown to be a suitable enzyme for use in the biodiesel production process.     

Biodiesel fuel production from plant oil catalyzed by Rhizopus oryzae lipase in a water-containing system without an organic solvent

A new enzymatic method of synthesizing methyl esters from plant oil and methanol in a solvent-free reaction system was developed. It is anticipated that such plant oil methyl esters can be used as a biodiesel fuel in the future. Lipase from Rhizopus oryzae efficiently catalyzed the methanolysis of soybean oil in the presence of 4-30 wt% water in the starting materials; however the lipase was nearly inactive in the absence of water. The methyl ester (ME) content in the reaction mixture reached 80-90 wt% by stepwise additions of methanol to the reaction mixture. The kinetics of the reaction appears to be in accordance with the successive reaction mechanism. That is, the oil is first hydrolyzed to free fatty acids and partial glycerides, and the fatty acids produced are then esterified with methanol. Although R. oryzae lipase is considered to exhibit 1(3)-regiospecificity, a certain amount of 1,3-diglyceride was obtained during the methanolysis and hydrolysis of soybean oil by R. oryzae lipase solution. Therefore, the high ME content in the reaction mixture is probably attributable to the acyl migration from the sn-2 position to the sn-1 or sn-3 position in partial glycerides.     

固定化Enterobacter agglomerans脂肪酶生产菜籽油生物柴油的研究

用硅藻土对实验室筛选得到的成团肠杆菌脂肪酶干燥酶粉进行固定化,固定化酶在有机溶剂体系下催化生产生物柴油。在最佳反应条件,即菜籽油15.47 mL,固定化脂肪酶用量1 000 U,甲醇为酰基受体(7.15 mL,3次等量加入),5 mL正己烷,振荡速度180 r/min,35℃反应48 h时,转化率达91.03%。实验结果表明,油酸含量高有利于生产生物柴油,而芥酸有不利影响。固定化酶稳定性好,重复使用8次,转化率仍大于50%,同时还具有一定的适应性,可催化大豆油和葵花籽油生产生物柴油。研究表明,固定化酶可用于催化生产生物柴油,并有效降低酶催化法的生产成本。     

助溶剂在生物柴油酯化反应过程中的促进作用

生物柴油是一种与石化柴油相比具有性能优势的可再生燃料,由动植物油等可再生原料与甲醇、乙醇等低碳醇经酯交换制得的脂肪酸单酯。生物柴油在全球范围内的逐步普及,对工艺过程和生产效率提出了更高的要求。由于助溶剂能够大大提高酯交换反应速率,从而提高生产设备的效率,降低能耗,故受到人们的普遍重视。根据各种助溶剂的性质,可将助溶剂划分为物质助溶剂和能量助溶剂,对酯交换过程中助溶剂加入的必要性,各种催化剂条件下助溶剂的使用特点,各种助溶方法的比较进行了介绍。     

Biodiesel fuel production from plant oil catalyzed by Rhizopus oryzae lipase in a water-containing system without an organic solvent

A new enzymatic method of synthesizing methyl esters from plant oil and methanol in a solvent-free reaction system was developed. It is anticipated that such plant oil methyl esters can be used as a biodiesel fuel in the future. Lipase from Rhizopus oryzae efficiently catalyzed the methanolysis of soybean oil in the presence of 4–30 wt% water in the starting materials; however the lipase was nearly inactive in the absence of water. The methyl ester (ME) content in the reaction mixture reached 80–90 wt% by stepwise additions of methanol to the reaction mixture. The kinetics of the reaction appears to be in accordance with the successive reaction mechanism. That is, the oil is first hydrolyzed to free fatty acids and partial glycerides, and the fatty acids produced are then esterified with methanol. Although R. oryzae lipase is considered to exhibit 1(3)-regiospecificity, a certain amount of 1,3-diglyceride was obtained during the methanolysis and hydrolysis of soybean oil by R. oryzae lipase solution. Therefore, the high ME content in the reaction mixture is probably attributable to the acyl migration from the sn-2 position to the sn-1 or sn-3 position in partial glycerides.     

高温气相色谱分析油脂转酯反应

建立了高温气相色谱分析油脂转酯反应样品中各种脂肪酸甲酯和脂肪酸甘油酯的方法。样品经硅烷化处理后分流进样,使用VF-5HT高温毛细柱,优化后的程序升温使各种脂肪酸甲酯和甘油酯得到良好分离,同时缩短了分析时间;十三酸甲酯和辛酸三甘油酯双内标分别对脂肪酸甲酯和脂肪酸甘油酯定量,提高了分析的准确度。该方法为油脂转酯反应制备生物柴油提供了分析依据。     

花椒籽油高纯度α-亚麻酸提取

以花椒籽油为原料,通过酯交换制备混合脂肪酸甲酯,利用尿素包合技术、硝酸银-硅胶柱层析法,对花椒籽油α-亚麻酸进行分离纯化,得到纯度高于92%α-亚麻酸产品.     

Impact of biodiesel source material and chemical structure on emissions of criteria pollutants from a heavy-duty engine

Biodiesel is an oxygenated diesel fuel made from vegetable oils and animal fats by conversion of the triglyceride fats to esters via transesterification. In this study we examined biodiesels produced from a variety of real-world feedstocks as well as pure (technical grade) fatty acid methyl and ethyl esters for emissions performance in a heavy-duty truck engine. The objective was to understand the impact of biodiesel chemical structure, specifically fatty acid chain length and number of double bonds, on emissions of NOx and particulate matter (PM). A group of seven biodiesels produced from real-world feedstocks and 14 produced from pure fatty acids were tested in a heavy-duty truck engine using the U.S. heavy-duty federal test procedure (transient test). It was found that the molecular structure of biodiesel can have a substantial impact on emissions. The properties of density, cetane number, and iodine number were found to be highly correlated with one another. For neat biodiesels, PM emissions were essentially constant at about 0.07 g/bhp-h for all biodiesels as long as density was less than 0.89 g/cm3 or cetane number was greater than about 45. NOx emissions increased with increasing fuel density or decreasing fuel cetane number. Increasing the number of double bonds, quantified as iodine number, correlated with increasing emissions of NOx. Thus the increased NOx observed for some fuels cannot be explained by the NOx/PM tradeoff and is therefore not driven by thermal NO formation. For fully saturated fatty acid chains the NOx emission increased with decreasing chain length for tests using 18, 16, and 12 carbon chain molecules. Additionally, there was no significant difference in NOx or PM emissions for the methyl and ethyl esters of identical fatty acids.     

黏度法快速测试生物柴油连续生产酯交换反应转化率

对黏度法测试生物柴油连续生产酯交换反应转化率过程的可行性和准确性进行了系统研究。结果表明:采用黏度法测试酯交换反应转化率是可行的,且具有较高的准确性;生产条件下采用黏度法,甲醇导致黏度急剧降低,甘油使黏度略有增加,而碱催化剂影响可以忽略;取样点确定为沉降工序后上层甲酯,样品蒸发除甲醇进行黏度测试。与色谱法对比,平均相对标准偏差为0.91%,可用于实际生产过程酯交换反应转化率的快速测试。     

Lipase-catalyzed process in an anhydrous medium with enzyme reutilization to produce biodiesel with low acid value

One major problem in the lipase-catalyzed production of biodiesel or fatty acid methyl esters (FAME) is the high acidity of the product, mainly caused by water presence, which produces parallel hydrolysis and esterification reactions instead of transesterification to FAME. Therefore, the use of reaction medium in absence of water (anhydrous medium) was investigated in a lipase-catalyzed process to improve FAME yield and final product quality. FAME production catalyzed by Novozym 435 was carried out using waste frying oil (WFO) as raw material, methanol as acyl acceptor, and 3 Å molecular sieves to extract the water. The anhydrous conditions allowed the esterification of free fatty acids (FFA) from feedstock at the initial reaction time. However, after the initial esterification process, water absence avoided the consecutives reactions of hydrolysis and esterification, producing FAME mainly by transesterification. Using this anhydrous medium, a decreasing in both the acid value and the diglycerides content in the product were observed, simultaneously improving FAME yield. Enzyme reuse in the anhydrous medium was also studied. The use of the moderate polar solvent tert-butanol as a co-solvent led to a stable catalysis using Novozym 435 even after 17 successive cycles of FAME production under anhydrous conditions. These results indicate that a lipase-catalyzed process in an anhydrous medium coupled with enzyme reuse would be suitable for biodiesel production, promoting the use of oils of different origin as raw materials.     

预处理固定化脂肪酶催化合成生物柴油

探讨了预处理固定化Candida antarctica脂肪酶催化餐饮废油合成生物柴油的过程。将固定化Candida antarctica脂肪酶用叔丁醇处理3h后再用废油浸泡4h，用于催化酯交换反应，酯交换反应速率明显加快。研究发现，固定化Candida antarctica脂肪酶预处理后，过量甲醇对酶的抑制作用仍然存在。采用分步添加甲醇工艺，按总醇油摩尔比3：1，分别在0、0．5、1．0、1．5、2．0、2．5h等量加入甲醇，反应4h后，体系中甲酯含量达到97．86％，反应：效率是未处理固定化酶催化合成生物柴油体系的6倍。固定化酶重复使用仍具有较高活性。     

液相色谱法测定生物柴油中多种脂肪酸甲酯

采用液相色谱法分离,液相色谱—质谱联用及标准品对照法对由菜籽油制备生物柴油中各种脂肪酸甲酯进行定性,并利用外标法建立准确测定生物柴油中各种脂肪酸甲酯组成及含量方法。试验结果表明,利用该法,生物柴油中各脂肪酸甲酯均能达到基线分离,且线性关系良好,相关性系数均在0.998以上,回收率达95.4%～104.1%;该法简单快速、准确性好。     

微生物脂肪酶的研究与应用

脂肪酶是一类能够催化酯的水解反应以及在非水相体系中催化脂肪酸和醇类发生酯化反应的酶类。随着酶学技术的快速发展,微生物脂肪酶也受到了越来越多的关注。作为生物催化剂,脂肪酶一直以来都是生物技术领域中最重要的一类酶。本文探讨了脂肪酶的来源、理化性质、脂肪酶活力测定,同时对脂肪酶的非水相催化特性以及脂肪酶在食品工业,医药、洗涤剂、皮革、造纸和生物柴油工业领域中的应用进行了讨论。     

Direct transesterification of total fatty acids of adipose tissue, and of freeze-dried muscle and liver with boron-trifluoride in methanol

The purpose of this study was to demonstrate direct transesterification of fatty acids of tissue total lipids with boron-trifluoride in methanol. Adipose tissue, muscle, and liver samples obtained from market-weight lambs, were transesterified with 14% boron-trifluoride in methanol at 80 °C. Total lipids of additional samples were first solvent-extracted and then transesterified with 14% boron-trifluoride in methanol. Thin layer Chromatographic evaluation revealed quantitative conversion of triacylglycerol- and polar lipid-fatty acids to fatty acid methyl esters using direct transesterification. No differences in fatty acid composition were observed for adipose tissue (p > 0.05); however, for muscle, 20:4 was greater (p = 0.01) with direct transesterification. For liver, greater concentrations of fatty acids were observed for the direct transesterification method (p < 0.02). Weight percentages of adipose and muscle fatty acids were unchanged from 15 to 180min of direct transesterification; however, 120 and 90 min of direct transesterification were required for adipose tissue and muscle, respectively, for complete transesterification. It was concluded that for analysis of total fatty acids, one-step direct transesterification with boron-trifluoride in methanol is a useful and acceptable procedure.     

Purification and characterization of lipase from Rhizopus chinensis cells

Lipase from Rhizopus chinensis cells was purified and characterized. The molecular mass of purified lipase was 28.4 kDa and the optimal temperature and pH for its activity were 37 degrees C and 5.5, respectively. Purified lipase exhibited high hydrolytic activity against fatty acid methyl esters such as methyl caprylate, methyl laurate, and methyl palmitate. Freeze-dried lipase catalyzed the transesterification between olive oil and methyl laurate in n-hexane.     

超临界甲醇法制备生物柴油工艺探讨

该实验对制备生物柴油几种影响因素进行探索,实验结果表明,在350℃、15MPa、醇油比为20:1和反应时间为30min条件下,反应转化率可达95%以上;且经过真空精馏后得到生物柴油产品甲酯含量可达98.7%以上,水洗和干燥后产品性能符合美国生物柴油标准。另外,该研究还在甲醇和油料中分别加入不同比例水和油酸进行实验,发现超临界法制备生物柴油不受水和游离酸影响。     

培养过程参数对霉菌Rhizopus oryzae IFO细胞催化植物油脂合成生物柴油的影响研究

采用脂肪酶催化可再生动植物油脂合成生物柴油已经成为目前研究的热点,其中利用全细胞催化剂是一个重要的研究方向。文中直接利用霉菌R.oryzaeIFO细胞催化植物油脂甲醇解反应合成生物柴油,系统研究了培养过程参数对细胞生长和该细胞催化剂催化甲醇解反应活性的影响。研究表明,细胞培养过程中所添加的油脂不同,细胞在后续反应中催化特定油脂进行生物柴油制备时所表现出的催化活性也会有所差别;由某种油脂作为碳源得到的细胞催化剂催化对应油脂与甲醇转酯化反应制备生物柴油时,表现出比催化其他油脂和甲醇反应制备生物柴油更高的催化活性。在优化的操作参数(大豆精制油20g/L,蛋白胨70g/L,NaNO31.2g/L,KH2PO41.2g/L,MgSO4·7H2O0.5g/L,培养温度35℃,摇床转速130r/min)下,培养得到的细胞催化剂能有效催化大豆油与甲醇三步转酯化反应,生物柴油(脂肪酸甲酯)最终得率可达到86%。     

酶法催化酯交换反应制备脂肪酸甲酯工艺研究

利用凯泰中性脂肪酶催化菜籽油与甲醇酯交换制备脂肪酸甲酯,相比而言,采用经乳化后菜籽油作反应原料具有更高转化率;为提高转化率,采用响应面实验设计和分析方法对菜籽油酯交换反应条件进行优化,得到最佳工艺条件:反应温度47℃,反应时间34小时,醇油摩尔比为4.5∶1,脂肪酶用量420UI;在此工艺条件下,酯交换反应转化率达95.81%。采用GC–MS技术分析所得样品,结果表明,菜籽油脂肪酸甲酯主要组份为油酸甲酯。