Emulsifying capacity of a biosurfactant extract obtained from a residual corn stream by pilot-scale dialysis process

Abstract

1. Introduction - The ATEMBIO project explores the use of membrane technology, particularly diffusion dialysis, as a strategy to recover biosurfactants (BS) from corn steep waters (CSW), aiming to achieve a technology readiness level (TRL) between 4-6. In this context, dialysis is proposed as an innovative and environmentally sustainable approach for the downstream processing of secondary metabolites. Therefore, the obtained BS extract by pilot-scale dialysis process could be considered as potential ingredient for cosmetic applications. 2. Experimental - A pilot-scale dialysis unit, manufactured by Mech-Chem (USA), equipped with 6-8 kDa regenerated cellulose membranes were used to process CSW in an open configuration at 4ºC. Centrifuged and pH-adjusted (pH 6.5) CSW was pumped at 0.56 L/h·m2 to the dialysis unit and counter current was pumped Milli-Q water at 1.90 L/h·m2. Once the BS extract has been obtained, it is freeze-dried for different assays. The study variables included the type of BS extract (lab-scale and pilot-scale dialysis processes), the BS extract concentration (0.5 and 1% w/v), and different types of mica (M010, M75, and M600) with particle size from 6.5 to 354.9 μm. In this way, emulsifying capacity was carried out by mixing mica (1% w/v), BS extract in aqueous solution (0.5 or 1% w/v) and finally tocopherol (50% w/v) in a total emulsion volume of 4 mL. Mixtures were homogenized using vortex for 2 minutes at room temperature. Emulsion height was measured for 1 month to determine relative emulsion volume (EV%) and stability (ES%). Furthermore, the volume (%) and particle size (μm) distribution of emulsions was assessed by dynamic light scattering (DLS) in the particle size range from 40 nm up to 2000 μm using a particle size analyzer model LS 13 320 (Beckman Coulter, Spain); and the emulsion droplets were observed under a Nikon Eclipse E800 optic microscope equipped with a Nikon camera. All assays were carried out following the procedure described in previous works and performed in triplicate [1]. 3. Results and Discussion - The emulsion results indicate that the BS extract concentration plays a key role, being required a concentration of 1% to achieve EV values of around 70%. Regarding the type of BS extract, the extract obtained through the pilot-scale dialysis process showed better performance for all the micas tested. Concerning the type of mica, M010 and M75 exhibited very similar EV values, ranging from 59 to 69.8%, whereas the best results were obtained with mica M600, with values between 59 and 75.1%. In this last case, Pickering emulsions displayed ES values of 95% in the presence of the BS extract from pilot-scale dialysis process and 61% in its absence after one month. 4. Conclusions - This study demonstrates the successful production of a biosurfactant extract using a pilot-scale dialysis process as an alternative to conventional biosurfactant recovery methods. Its emulsifying property highlights its potential for promising applications in the cosmetics sector.