Integrated systems for biosurfactant synthesis

Biosurfactants are difficult to produce in an economic manner for several reasons: 1. Overproducing strains of bacteria are rare and those found generally display a very low productivity. In addition complex media need to be applied. 2. The regulation of biosurfactant synthesis is hardly understood, seemingly it represents a "secondary metabolite" regulation. Among others 02-limitation has been described as an essential parameter to govern biosurfactant production. 3. An improvement of the production yield is hampered by the strong foam formation. Consequently diluted media have to be applied and only immobilized systems provided an increased productivity of about 3 g 1-1 h-1. In the following improved cultivation methods with developed defined media are described leading to enhanced productivities with the potential of 5 to 10 g 1-1 h-1 upon optimization of the bleeding rate of an integrated continuous process. Instead of indirect product analytics by physical methods (ChlC, surface tension) HPLC analysis for a new biosurfactant has been developed. INTRODUCTION Due to their biodegradability biosurfactants were originally ment to replace chemically synthesized surface active molecules (1, 2). However it has to be stated that the expected breakthrough in terms of applications of these biosurfactants has not yet occured. Among the reasons for this finding are the high production costs of biosurfactants, the limitation in the use of diluted media, technical difficulties encountered in the production process, in particular the strong formation of foam. In addition, the strains used often suffer from a bad public acceptance, such as P . aeruginosa. Fundamental improvements are therefore necessary as the required performance is not yet guaranteed. In the following the results achieved using direct analytics (HPCL) instead of indirect product determination (CMC, surface tension) with improved, yet simple and effective culture systems for preliminary testings are presented. As a model application this system was successfully applied to the design of defined media to replace expensive complex media which are generally far more difficult to handle. In addition efforts were made to replace the harmful strain P. aerugiitosa by P . fluorescens. In a second step an integrated system for a high perfomiance continuous production process was developed. By applying a highly effective membrane technology for cell retention a dramatic increase in potential product yield was achieved. RESULTS In order to improve the analytics of biosurfactants the production of these surface active molecules by Bacillus licheniformis in batch culture was investigated. B. licheniformis produces biosurfactants with a basic structure of a cyclic peptide of 7 amino acids with different B-OH fatty acid side chains (6, 8). For the product determination no easy and