The Study Of Induction And Immbolization Of Streptomyces Albus Which Can Biotransformate DHEA

Hollow calcium alginate capsules come from hollow calcium alginate gel beads, itis a kind of immobilized material which has the characteristics of low price, widesources and universal applications.With it we can produce compounds such as7αor7β-OH-DHEA which have more significant antioxidant activity and antitumoreffect.This method not only avoids the high cost and by-products produced by chemicalmethod, but also overcome the long conversion cycle and separation difficulties ofcommon biological transformation. Therefore, biological transformation of DHEA toproduct7α or7β-OH-DHEA is becoming a hot spot of current research, and is gettingmore and more favor from people.This article selected a type of strain streptomyces albus as the only species whichhad the good transforming activity, we also made the morphology observation andidentification of the bacteria. By single factor experiment, we optimized thebiotransformation conditions of the bacteria as follows: temperature30℃, optimumrevolution180r/min, pH7, spore concentration106/mL, additive time of substrate was48h, additive amount of substrate was60mg, optimum conversion time was48h, we gota elevation of the transformation rate of DHEA by streptomyces albus from30%to45%after optimization. In order to further enhance the conversion rate of the target product,we carried on the induction of Streptomyces albus and got the optimum concentration ofinducer as follows:methanol50μL，ethanol100μL, n-hexane200μL, carbamazepineconcentration5g/L, dilantin concentration1g/L, rifampicin concentration4g/L. We alsoconfirmed that ethanol and n-hexane were the best inducers which can make theconversion rate up to50%.Then we succeeded in preparing the hollow calcium alginate capsμLes by CMC,CaCl2and SA. Through the investigation of capsμLe performance and the ability to be aball, we confirmed the optimum conditions: SA concentration1%(w/v，1g/100mL，thesame below), CMC concentration1%, CaCl2concentration8%, addition speed200/min,churning time10min, needle aperture2mm, addition height8cm.Finally, we used hollow calcium alginate capsμLes to realize the immobilization ofstreptomyces albus, and confirmed that the immobilized bacteria had the transformationactivity on DHEA, and optimized the transformation conditions of immobilized bacteriaon DHEA, at last we got a37%transformation rate of immobilized bacteria for the first, 50%for the second time and so on. The experiment also analysed the influence ofgrowth conditions and bacteria volume of streptomyces albus in capsμLes on thetransformation rate of DHEA, we also realized the recycle of immobilized bacteria, andgot the high transformation rate of the second transfer. In order to improve thetransformation rate of the immobilized bacteria, we used inducer to induce theimmobilized bacteria, and made the first transformation rate up to49%.