Biotransformation of codeine to morphine in freely suspended cells and immobilized cultures of Spirulina platensis

Both freely suspended cells and immobilized cultures of Spirulina platensis , a blue-green alga, biotransformed exogenously fed codeine, an opium alkal oid, to morphine. The external addition of codeine to the culture medium di d not affect the growth of S. platensis. Immobilization of Spirulina in a c alcium alginate gel matrix was optimized by using 2% (w/v) sodium alginate and reducing the concentration of nutrients of Zarrouk's medium, which caus ed destabilization of the calcium alginate gel. The accumulation of morphin e increased gradually and reached maxima of 330 mu g 100 ml(-1) culture at 105 h in freely suspended and 351 mu g 100 ml(-1) at 96 h in immobilized Sp irulina cultures. Accumulation of morphine was detected only in the medium, whereas cells did not show accumulation. The immobilized Spirulina culture s showed marginally higher conversion of codeine to morphine over freely su spended cultures.