Simplified soy molasses-based medium for reduced-cost production of sophorolipids by Candida bombicola

Authors: Solaiman, Daniel; Ashby, Richard - Rick; Zerkowski, Jonathan; Foglia, Thomas

Submitted to: Biotechnology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2007
Publication Date: 7/30/2007
Citation: Solaiman, D., Ashby, R.D., Zerkowski, J.A., Foglia, T.A. 2007. Simplified soy molasses-based medium for reduced-cost production of sophorolipids by Candida bombicola. Biotechnology Letters. DOI 10.1007/S10529-007-9407-5.

Interpretive Summary: Sophorolipids (SLs) are biological detergents (biosurfactants) produced by yeasts grown on renewable agricultural feedstocks. SLs can replace petrochemical-based detergents in many applications such as cleaning solutions and washing detergents. In addition, they can be used as emulsifying agents, antimicrobial additives and cosmetic ingredients. The components of sophorolipid are also valued as starting materials for making biobased plastics and lubricants and for use as bioactive molecules to stimulate biomass degradation. There is, however, a need to lower the production cost of SL to make it more affordable to the end-users. One approach to achieve a lowering of production cost is to reduce the costs of the starting feedstocks. We have previously shown that a low-value coproduct of soy processing, i.e., soy molasses, could be used to produce SLs. In this study, we further show that by using soy molasses as a feedstock for SL production, two other expensive ingredients of the growth medium, i.e., yeast extract and urea, can be omitted, thus achieving a further cost reduction. The composition and detergent properties of the SL obtained from our study are compatible to those of SLs produced using more expensive ingredients. This work helps pave the way for future research to develop a cost-effective SL production system using the inexpensive soy molasses.

Technical Abstract: A simplified medium containing only soy molasses and oleic acid as ingredients was developed for the production of sophorolipids (SLs) from Candida bombicola. We achieved a product yield of 53 plus/minus 3 g of purified sophorolipids per liter of starting culture volume, which is 71 plus/minus 4% of the yield obtained with growth medium containing the costly yeast extract and urea as nitrogen source. The large majority of the SL components existed in the lactone form (87%), and the predominant component is SL containing (omega-1)-hydroxyoleic acid as the lipid moiety. The study demonstrated for the first time the usefulness of the low-value soy molasses as a combined nitrogen- and carbon-source for SL production at a reduced cost.