Abstract: The invention relates to a new microbiological process for the preparation of clavine alkaloids of the general formula (I), ##STR1## wherein R stands for hydroxymethyl or methyl group, by cultivation of a Claviceps fusiformis strain in liquid submerged culture medium containing sources of carbon, nitrogen, mineral salts and optionally other additives, under aerobic conditions, in which a Claviceps fusiformis variant strain deposited under No. 00211 is used as alkaloid-producing strain. The invention further relates to a biologically pure culture of the Claviceps fusiformis variant strain No. 00211 obtained in a process in which a Claviceps fusiformis strain No. 00164 is grown in a solid culture medium containing sources of carbon, nitrogen, mineral salts and agar as well as an additive promoting the formation of cytochrome P-450, followed by the selective isolation of the new strain No. 00211.

Abstract: Microbiological conversions of cyclodextrins are intensified by adding to the reaction mixture 0.2 to 3 moles of .alpha.-, .beta.- or .gamma.-cyclodextrin or an optical mixture thereof pro mole of the steroid substrate, before, at the beginning or during the conversion. The cyclodextrin if desired, can be removed after the reaction. In this way the reaction velocity can be increased, the reaction time is reduced, the substrate concentration in the solution, i.e. its solubility is increased or the so called product inhibition may be avoided. In certain cases of more alternatives the desired reaction can be catalyzed and in this manner the selectivity is increased.