비식용 원료인 Palm Acid Oil, 동물성 폐유지 등은 상대적으로 자유 지방산 함량이 높기 때문에 일반적인 염기 촉매를 이용한 전이에스테르화 반응에 적합하지 않다. 효소 촉매를 이용하면 염기 촉매에서 해결할 수 없는 몇 가지 문제를 해결할 수 있으며, 에너지 소비가 작고, 바이오디젤 부산물인 글리세롤 회수가 쉬우며, 자유 지방산 함량이 높은 트리글리세라이드에 대한 전이에스테르화 반응이 가능하다. 본 연구에서는 고정화 효소 촉매를 이용하여 1 ton/day 용량의 반응기에서 비식용 폐유지를 바이오디젤로 합성하였으며, 반응 공정의 변수를 최적화하였다.

Biodiesel as methyl esters derived from vegetable oils has considerable advantages in terms of environmental protetion. In the present work, methyl esters were produced from soybean oil by lipase-catalyzed transesterification. To reduce inactivation of commercial immobilized lipases emulsified two-step process was developed using the stepwise addition of methanol with 4:1 molar ratio at 4h intervals. Also with immobilized lipase from Candida antarctica(Novozym 435) high conversion of 98.5 percent was possible at 45℃ of reaction temperature with 4:1 of methanol-to-oil molar ratio and 1%(v/v) methyl glucoside oleic polyester as an emulsifier in the presence of cosolvent.

Lipases catalyzed the transesterification reaction between esters and various primary and secondary alcohols in a 99% organic medium, porcine pancreatic, yeast, mold lipases can vigorously act as catalysts in a number of nearly anhydrous organic solvents. Various transesterification reactions catalyzed by porcine pancreatic lipase in hexane obey Michaelis-Menten kinetics. The dependence of the catalytic activity of the enzyme in organic media on the pH of the aqueous solution from which it was recovered is bell-shaped, with the maximum coinciding with the pH optimum of the enzymatic activity in water. The catalytic power exhibited by the lipases in organic solvents is comparable to that displayed in water. In addition to transesterification, lipases Can catalyze several other processes in organic media.

This study investigated the optimal sequential hydrolysis conditions by comparing with reducing sugar yield ofsequential hydrolysis of Laminaria japonica processing residue. After acid-catalyzed hydrothermal hydrolysis, sequentialenzymatic hydrolysis was performed with single enzymes such as Celluclast® 1.5L, Saczyme, and Alginate Lyase, andtheir mixture. As a result, the yield of reducing sugar by sequential hydrolysis with the mixed enzymes was the highest,but there would be an economical problem with excessive enzyme loading. Therefore, considering the reducing sugaryield and economics, it is thought that hydrolysis by the mixed enzymes has no advantage, thus, using the Celluclast®1.5L in the sequential hydrolysis was practically more appropriate. The optimal sequential hydrolysis conditions ofLaminaria japonica processing residue were determined to be 8% v/w of enzyme injection, 42.6oC of reaction temperature,pH 4.1, and 26 hours of reaction time after acid-catalyzed hydrothermal hydrolysis (0.108 N-HCl, 144oC of reactiontemperature, and 22 minute of reaction time).

Since biodiesel as bioenergy is defined as ester compounds formed by esterification of animal/vegetable oils, in this study three vegetable cooking oils (market, waste and refined waste ones) were esterified by reactions of alkali catalyst and immobilized enzyme. The fatty acid composition of the formed ester compounds was analyzed to investigate the feasibility of biodiesel production. By lipolysis (i.e, hydrolysis of Triglyceride (TG)), all three vegetable oils used in this study were found to produce Diglyceride (DG), Monoglyceride (MD) and Fatty acid ethylester (FAEE). However, the amount of produced FAEE (which can be used as an energy source) was in the increasing order of market cooking oil, waste one and refined waste one. With NaOH catalyst, FAEE was produced about 24.92, 17.63 and 11.31 % for the respective oils while adding Lipozyme TL produced FAEE about 43.54, 38.16 and 24.47 %, respectively. This indicates that enzyme catalyst is more effective than alkali one for transesterification. In addition, it was found that the composition of fatty acids produced by hydrolysis of TG was unchanged with alkali and immobilized enzyme reactions. Thus it can be expected that stable conditions remain in the course of mixing with gasoline whose composition is similar to that of the fatty acids.