A comprehensive screening platform of wood-derived sugars for sophorolipid production: predictive modelling, sterilization methods and analysis of feedstock composition.

Sophorolipid production using conventional food-grade feedstocks such as glucose and rapeseed oil can have detrimental impacts on food supply and commodity prices. The increasing complexity of alternative feeds necessitates efficient management of nutritional (substrate and inhibitor content) and physical (viscosity, particulates) characteristics. To address this, a screening platform was applied that uses predictive modelling to customize the fermentation media composition based on feed substrate content, while employing different preparation methods such as tangential flow filtration or autoclaving to mitigate particulate loading and prevent the formation of inhibitory by-products. To validate the platform, three lignocellulosic sugars (Fibenol OÜ) were tested, including the glucose-rich (C6), xylose-rich (C5), and mixed (C5/C6) sugars. Under the tailored media conditions, the C6 wood-sugar produced 47.12 g/L and 44.33 g/L average sophorolipid with tangential flow filtration and autoclave sterilization, respectively. The C5/C6 wood-sugar only produced sophorolipid with tangential flow filtration (40.15 g/L) whilst the C5 wood-sugar did not produce sophorolipids with either sterilization method. Comparatively, autoclaved glucose produced 33.06g/L average sophorolipid under conditions matching the C6 and C5 wood-sugars. The combination of predictive profiling and preparation method comparisons allows for effective screening of potentially productive fermentation feeds, with the application of tangential flow filtration for feeds being reported for the first time.

Highlights:

• The application of tangential flow filtration to fermentation feeds avoids the
   formation of inhibitory by-products.
• Glucose rich wood-derived sugars (C5 and C5/C6) were capable of producing
   more sophorolipids than a pure glucose equivalent at identical glucose
   concentrations
• Replacement of autoclaved C5/C6 sugars with a tangential flow filtered form
   brought production from 0 to 40.15 g/L average C18:1 lactonic diacetylated
   sophorolipid.
• The consumption of acetic acid appears to promote the consumption of
   rapeseed and subsequently increase sophorolipid production.
• The production of sophorolipids is associated with the formation of formic
   acid.

Keywords: sophorolipid, screening, S. bombicola, lignocellulose, tangential flow                   filtration