| In this paper, two bioconversion reactions, the 11 β -hydroxylation of Compound RSA and degrading the side chain of phytosterols , were researched in the present of β -CD. The mechanism of β -CD acting on steroid bioconversion was preliminarily discussed. The main research contents and results are as follows:The conditions of β -CD including Compound RSA was determined. On that condition, β -CD-RSA inclusion complex was made and then characterized with optical microscopy, FTIR, TG-DSC analysis. Concluded from stability of equilibrium constant, β -CD-RSA (molar ratio β -CD: RSA 1:1) was stable inclusion complex in water. Further research showed how β -CD included RSA. The effects of β -CD on RSA solubility were studied and it was found that the RSA solubility at 1:1 ratio of RSA to β-CD at 28℃ was 9.12 mg/L ,5.26 times higher than that without β -CD. β -CD-PS inclusion complex was also made and then characterized with X-Ray, TG-DSC analysis.The course of β -CD including Compound RSA was reversible and deeply affected by temperature. High temperature caused Compound RSA to release from β-CD. So when extracting product HC ,the culture firstly was heated to boil and then cool to 50℃. With the molar ratio of β -CD to Compound RSA increasing, HC conversion rate decreased from 59.72% to nearly none. Adding β -CD earlier than Compound RSA, the conversion velocity became slower. The two results showed that β -CD including Compound RSA limited bioconversion. The effects of β -CD on phytosterols bioconversion to AD(D) with Mycobacterium sp. were also investigated. With the molar ratio of β-CD to phytosterols increasing, AD(D) conversion rate decreased from 22% to 2%,compared with 29% of uncomplexed phytosterols dispersed with Tween 80.Compound RSA was absorbed by Absidia coerulea cells in the course of bioconversion ,which were observed under ESEM .The dry Absidia coerulea cells contained Compund RSA about 5.17mg/g.This further proved the conclusion made by observing under ESEM. The amount of Compund RSA in the dry Absidia coerulea cells was 49.94 times as much as the cells dealt with β -CD. β -CD extracted Compund RSA from Absidia coerulea cells. In the course of adding β -CD earlier than Compound RSA, the solubility of HC was higher than Compound RSA .It showed that β -CD departed HC from the cells.To make use of the ability to extract steroid from cell by β -CD, β -CD was added 3h later than Compound RSA . The conversion velocity was accelerated effectively because of HC reducing feedback inhibition.Further experiments proved that P -CD included lween80. When the TweenSO molecular was included, it lost the abilfty to emulsify hydrophobic substrates. So, firstly dispersed phytostesols with TweeaSO to redyce the acts between phytosterols molecular. ￡ -CD was added at the moment of Mycobacterium sp. cells in a great amount. The conversiott of phytosterols was 19.1% more than phytosterois only dispersed with Twees 8&. He conversion was strengtheaed becauce the acts between cells and phytostef ols were increasing,...
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