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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 transesterffying triglycerides with secondary alcohols to give branched a|kyl esters. Conditions were established for converting tallow to short-chain alkyl esters at more than 90% conversion. These same conditions also proved effective for transesterifying vegetable oils and high fatty acid-containing feedstocks to their respective alkyl ester derivatives.

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 7% was on the post-transesterification flakes.Paper no. J10571 in JAOCS 81, 83-89 (January 2004).KEY WORDS: Biodiesel, fats and oils utilization, fatty acid ester, in situ transesterification, transesterification.The simple alkyl esters of FA have numerous established uses in the food, textile, cosmetic, rubber and metal processing, and synthetic lubricant industries. FAME are the predominant esters consumed, with a year 2000 global consumption of 1 million metric tons (MMT) (1). In addition, FAME are the favored starting material for the production of fatty amides, more complex esters, ester sulfonates, and fatty alcohols. Fatty alcohols alone were consumed at a world rate of 6.2 MMT in 2000 (1). Production and consumption of the methyl esters of FA are rapidly increasing due to their growing use as biodiesel, a renewable replacement for petroleum-based diesel engine fuel.Contemporary industrial technology for the synthesis of fatty acyl esters of vegetable oils involves isolation of oilseed acylglycerides by extrusion or solvent extraction, degumming and refining of the oil, and its alkali-catalyzed transesterification. Hexane extraction is the main technology for oil recovery in the United States. Extraction plants achieve high levels of solvent recovery, with a typical soybean processing plant losing less than 1.25 L of solvent per metric to...

Aside from their importance to the survival and general welfare of mankind, agriculture and its related industries produce large quantities of feedstocks and coproducts that can be used as inexpensive substrates for fermentative processes. Successful adoption of these materials into commercial processes could further the realization of a biorefinery industry based on agriculturally derived feedstocks. One potential concept is the production of poly(hydroxyalkanoate) (PHA) polymers, a family of microbial biopolyesters with a myriad of possible monomeric compositions and performance properties. The economics for the fermentative production of PHA could benefit from the use of low-cost agricultural feedstocks and coproducts. This mini-review provides a brief survey of research performed in this area, with specific emphasis on studies describing the utilization of intact triacylglycerols (vegetable oils and animal fats), dairy whey, molasses, and meat-and-bone meal as substrates in the microbial synthesis of PHA polymers.