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With supercritical carbon dioxide as a reaction medium, the syntheses of cocoa butter equivalent by interesterification with various lipases were investigated. The study showed that among those five lipases tested, lipase IM-20 from Mucor miehei was the most effective and specific in synthesizing this cocoa butter equivalent product by interesterification. The yields of cocoa butter equivalent are affected by pressure, substrate oil composition, solubility and co-solvent. The best reaction conditions were: reaction pressure at 1500 psi, triglyceride with high content of POP (P, palmitate; O, oleate) and POO, reaction medium with 5.0% water, and reaction temperature at 50°C. The major component of cocoa butter, POS (S, stearate), can be increased by 6.0% by adding a small amount of carbon dioxide. The yield and melting point of the purified cocoa butter equivalent are 53.0% and 34.3°C, respectively.

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lrlgliluI[.' [If B(atany, ,'M adernia Sinica, Nankang,1 ,'.iplg, raiv,,,u~ 11 ~2!l, drlr, J /'D(?raarml(,t11 i.~r St,lld lel/hr~ologv, Td.illl.,i, Ta!wan ]11 ABSTRACT: ViJlrio mimicu,~ arylesterase, a 20 kDa protein, is a nlultiiuln~ tifma] enzyme with Ihioe,qer,tse at:<] chyl~qntl-yl)sin-like activilies, gecaLise an aflinily His-tag ,:six consecutive his{idin0 affinily' tag:l clirectly, [o the prnh.qn cau,4~d Ihe loss of enzyllq[? aLtivity, a hr,.,xade(-a]X':l::.tide v,.,itl'. His-tag, A1)I'NSSSVf)K1.AAAL.r_-HHH1-]HH encoded from vector pET-2Ob,:+i was (.iJllS]l-Ut:l(xt [{I ,Pxlen(J (mnl the carboxyl tr,_'lnlil~uls of the arvlesterase. This His. taggell pr~lein r,~:,[a]rqr,.,.(] enzyme fLJn,r..-ti,r'l~,S. Thermal unroh-ling l>e. hm,.'i[~r ol l~oIh proteins was ahnosl identical, and lheir T vakles were near 54:>(.7 as rnonilored 1),,. cilr.:ular dicl:,loism. l-ryl:>tic ,: le,tvage of lhe I'un~:tiemal His-tagged enzyme fm~du,:ed 1,a.'o smaller i)rGeins, which slill i~{~ssessed enZynlC a(_livily and whi{ h suggeslt.,ct [hal the addilii~na] ]leptide extended ~)n the i:~rotc.in ~t_tr'-Iat:e. fl',tt spa( htg pepfide hetweerl His-tag and arylesterase successlullv FXeVenle,d tl'i{, iNlerr'erulce of lhe His-tag to the enzyme functions. lhu kh~,:,li,: sludies sh(),,.ve~l ~l~( the wild q,'pe. /A(.)C5 74. 1}7l-1:176,:1 !;97).