Investigation on Applying Cyclodextrins in a Fermentation Process for Enhanced Biosurfactant Production by Bacillus licheniformis

Biosurfactants are environmentally friendly alternatives for chemical surfactants and have a broad spectrum of applications in different industries such as cosmetics, oleochemistry, pharmaceuticals, and detergents. It has been established that Bacillus licheniformis produces several lipopeptide-type biosurfactants, including lichenysin and iturin. However, in order to enhance the biosurfactant production by Bacillus licheniformis, it is necessary to either extend the already performed media optimization to circumvent the current limitations or defeat the product inhibition. Cyclic oligosaccharides made of glucose monomers called cyclodextrins (CD) have been shown to improve the biomass synthesis of other microorganisms, which may also increase the output of biosurfactants. The efficient fermentative production of biosurfactants is often limited by the inhibitory/toxic effect of the product on the producer cells itself. Therefore, in this work, we demonstrated that CDs may entrap biosurfactants from the broth, decreasing product inhibition. Thus, we also tested the media supplementation with three different types of cyclodextrins including alpha-, beta-, and gamma-CD and a derivative (dimethyl-beta-cyclodextrin, DIMEB); notably, DIMEB at 2.0 g/L enhanced biosurfactant production by up to 41.43% and specific product formation (g product/g cells) by 79,6% compared to the control, while mitigating the growth inhibition observed at lower concentrations. This study demonstrates, for the first time, the distinct advantage of DIMEB over native CDs in reducing product toxicity and boosting biosurfactant yields, highlighting its potential as a simple additive strategy for improving sustainable bioprocesses.