William N. Marmer

Abstract Lipases were screened for their ability to transesterify triglycerides with short‐chain alcohols to alkyl esters. The lipase from Mucor miehei was most efficient for converting triglycerides to their alkyl esters with primary alcohols, whereas the lipase from Candida antarctica was most efficient for transesterifying triglycerides with secondary alcohols to give branched alkyl esters. Conditions were established for converting tallow to short‐chain alkyl esters at more than 90% conversion. These same conditions also proved effective for transesterfying vegetable oils and high fatty acid‐containing feedstocks to their respective alkyl ester derivatives.

Abstract The production of simple alkyl FA esters by direct alkali‐catalyzed in situ transesterification of the acylglycerols (AG) in soybeans was examined. Initial experiments demonstrated that the lipid in commercially produced soy flakes was readily transesterified during agitation at 60°C in sealed containers of alcoholic NaOH. Methyl, ethyl, and isopropyl alcohols readily participated in the reaction, suggesting that the phenomenon is a general one. Statistical experimental design methods and response surface regression analysis were used to optimize reaction conditions, using methanol as alcohol. At 60°C, the highest yields of methyl ester with minimal contamination by FFA and AG were predicted at a molar ratio of methanol/AG/NaOH of 226∶1∶1.6 with an approximately 8‐h incubation. An increase in the amount of methanol, coupled with a reduced alkali concentration, also gave high ester yields with low FFA and AG contamination. The reaction also proceeded well at 23°C (room temperature), giving higher predicted ester yields than at 60°C. At room temperature, maximal esterification was predicted at a molar ratio of 543∶1∶2.0 for methanol/AG/NaOH, again in 8 h. Of the lipid in soy flakes, 95% was removed under such conditions. The amount of FAME recovered after in situ transesterification corresponded to 84% of this solubilized lipid. Given the 95% removal of lipid from the soy flakes and an 84% efficiency of conversion of this solubilized lipid to FAME, one calculates an overall transesterification efficiency of 80%. The FAME fraction contained only 0.72% (mass basis) FFA and no AG. Of the glycerol released by transesterification, 93% was located in the alcoholic ester phase and 75 was on the post‐transesterification flakes.

Abstract FAME of lard, beef tallow, and chicken fat were prepared by base‐catalyzed transesterification for use as biodiesel fuels. Selected fuel properties of the neat fat‐derived methyl esters (B100) were determined and found to meet ASTM specifications. The cold‐flow properties, lubricity, and oxidative stability of the B100 fat‐derived fuels also were measured. In general, the cold‐flow properties of the fat‐based fuels were less desirable than those of soy‐based biodiesel, but the lubricity and oxidative stability of the fat‐based biodiesels were comparable to or better than soy‐based biodiesel. Nitrogen oxide (NO x ) emission tests also were conducted with the animal fat‐derived esters and compared with soybean oil biodiesel as 20 vol% blends (B20) in petroleum diesel. The data indicated that the three animal fat‐based B20 fuels had lower NO x emission levels (3.2–6.2%) than did the soy‐based B20 fuel.

A method for lipid isolation is presented that is alternative to the traditional chloroform/methanol extraction methods. This new method allows lipid isolation by solvent elution of a dry column composed of a tissue sample, anhydrous sodium sulfate, and Celite 545 diatomaceous earth ground together. To isolate total lipids, the dry column is eluted with a mixture of dichloromethane/methanol (90:10, v/v). Alternatively, the lipids may be isolated and simultaneously separated into neutral and polar fractions by a sequential elution procedure; neutral lipids free of polar lipids are eluted first with dichloromethane, followed by elution of polar lipids with the dichloromethane/methanol (90:10) mixture. The two dry column methods-isocratic or sequential elution-were compared with the traditional chloroform/methanol methods by gravimetric, thin layer chromatographic and phosphorus analyses.