Maltosy-$eta$-cyclodextrin는 $eta$-cyclodextrin에 maltose가 $Alpha$-1,6 glycosidic bond로 결합된 분지환상결합체로서 pullulanase의 역반응(축합반응)을 이용하여 $eta$-cyclodextrin과 maltose로부터 합성된다. Maltosyl-$eta$-cycloextrin의 합성수율을 증가시키기 위하여 각종 water activity depressor인 각종 polyol, sugar 그리고 polyethylene glycol(PEG)등의 첨가의 영향을 검토하였다. 가장 적절한 water activity depressor는 PEG 6000로서, 첨가량 10%(w/w)의 경우 maltosyl-$eta$-cyclodextrin 생성량과 합성수율은 크게 증가하여 3.02g/100ml 와 55.9%(w/w)로서, 첨가하지 않았을 경우보다 약 1.3배 증가하였다. Water activity는 PEG 6000을 20%(w/w) 첨가할 때 원래의 0.966에서 0.914로 감소하였으며, maltosyl-$eta$-cyclodextrin 합성수율은 water activity에 반비례하여 증가하였다. Pullulanase의 역반응을 이용한 maltosyl-$eta$-cyclodextrin 합성반응의 각종 열역학적 상수를 평가하였으며, $Delta$H는 36.788kJ/mol, $Delta$S는 0.067kJ/moleK, 그리고 $Delta$G는 14.433kJ/mole이였다. PEG 6000의 분리회수에 적절한 ultrafiltration membrane의 pore size는 3K dalton이었으며, 여과액과 농축액의 적정 분획비는 1.0 : 9.0였다. Maltosyl-$eta$-cyclodextrin 합성수율의 증가는 첨가한 PEG가 water activity를 감소시켜 합성된 maltosyl-$eta$-cyclodextrin이 재분해되는 pullulanase이 정반응인 hydrolysis reaction을 억제하여 equilbrium state에 변화를 주기 때문인 것으로 유추된다.
The effect of various water-activity depressors, such as pol yo Is, sugars, and polymers, on the conversion yields of the enzymatic synthesis of maltosyl-$eta$-cyclodextrin from $eta$-cyc1odextrin and maltose through reverse reaction of pullulanase was investigated. PEG 6000 of concentration of 10% (w/w) was found to be the most acceptable water-activity depressor resulting for increment of conversion yield from 43.0% to 55.9%, corresponding maltosyl-$eta$-cyc1odextrin concentration of 3.02 g/100 ml H20. Water activity was changed from initial 0.966 to 0.914 upon addition of 20% (w/w) of PEG 6000. The conversion yields were inversely proportional to the water activities, and the increased conversion yield was caused by water activity depression which inhibited the hydrolysis reaction of maltosyl-$eta$-CD to maltose and $eta$-cyc1odextrin. The changes of enthalpy ($Delta$H), entropy ($Delta$S), and Gibbs free energy ($Delta$G) were calculated to be 36.788 kJ/mole, 0.067 kJ/mole K. and 14.433 kJ/mole, respectively. The synthesis of maltosyl-$eta$-CD could be increased substantially by the intermittent feeding of $eta$-cyclodextrin. PEG 6000 could be separated effectively from reaction mixture using ultrafiltration membrane for reutilization.
