Influence of Additives on the Biohydroxylation of Protected Carboxylic Acids and Ketones

Michaela Kreiner¹, Gerhart Braunegg¹*, Anna De Raadt², Herfried Griengl², I. Kopper¹, O. Sukcharoen¹, H. Weber<sup>2

1</sup>lnstitute of Biotechnology, Technical University of Graz, Petersgasse 12, 8010 Graz, Austria, Spezialforschungsbereich F01 Biocatalysis
²Institute of Organic Chemistry, Technical University of Graz, Stremayrgasse 16, 8010 Graz, Austria, Spezialforschungsbereich F01 Biocatalysis

Article history:
Received March 6, 1997
Accepted June 13, 1997

Key words:
biohydroxylation, 13-cyclodextrin, B. megaterium, B. bassiana, C. lunata, C. hlakesleeana, surfac­tants, cyclic carboxylic acids and ketones

Summary:
The effects of β-cyclodextrin (β-CD), the anionic detergent Witconate SK, two non-ionic surfactants, Triton X-100 and Tween 80, and sodium tetraborate on the biohydroxylation of protected cyclic carboxylic acids and ketones by Bacillus megaterium and the fungi Beauveria bassiana, Curvularia lunata, and Cunninghamella blakesleeana were studied in shake flask experiments. The bacterium B. megaterium was found to be more sensitive towards the above mentioned surfactants than the fungi tested. The presence of Triton X-100 (0.5 fold CMC) and Tween 80 (0.5-2.0 g L^-1) decreased the maximum concentration of the main hydroxylated product by 62% and 55%, respectively. Employing Witconate, hydroxylation ivas not observed at all. Only β-CD (0.5 g L^-1) proved to be slightly beneficial for the transformation using B. megaterium demonstrated by a 5% increase of the overall yield. Contrary to the results obtained with B. megaterium, the fungi under consideration showed an improvement, with respect to the biotransformation with all the additives tested. Generally low detergent concentrations (up to 1 g L^-1) were preferable. Most positive results for the transformation with C. lunata were found with 0.5 g L^-1 β-CD and 1 g L^-1 Tween 80 allowing a 65% increase of the maximum yield of the main hydroxylated product. The presence of 12 mg V sodium tetraborate increased the maximum concentration of the main product when employing C. blakesleeana. For B. bassiana, a 33% increase of the maximum product concentration zvas obtained in the presence of Witconate (0.5 and 1.0 g L^-1).