High-Value Added Valorization of Food Waste Streams to Rhamnolipids

Globally, food waste constitutes 30-50% of total municipal solid waste while landfilling remains the main treatment technology. From a circular economy perspective, this treatment option is not sustainable due to greenhouse gases emission and breakdown of nutrient cycling. Meanwhile, the recent sustainable development goals emphasize on food security, environmental protection and material and energy efficiency, and therefore, have become the key drivers for food waste valorization to high-value products. In the present work, we investigated the feasibility of bioconversion of mixed, post-consumption leftover food waste into rhamnolipids biosurfactant using Pseudomonas aeruginosa. Food waste was obtained from university cafeteria in Hong Kong. The food waste hydrolysate was obtained by mixed culture acidogenic fermentation instead of using expensive commercial enzymes. Preliminary experiments compared the rhamnolipids production efficiency on (food) waste streams including waste cooking oil and mixed food waste with refined hydrophilic substrates such as glucose and glycerol, and hydrophobic carbon sources such as oleic acid and fresh canola oil. Food waste emerged as the best feedstock for rhamnolipids production and was subsequently used for fermentation in a laboratory bioreactor. Characterization of produced rhamnolipids was performed by Liquid Chromatography with tandem Mass Spectrometry (LC-MS/MS) and Fourier Transform Infrared Spectroscopy (FTIR). It was shown that food waste-derived rhamnolipids predominantly contained Rha-C10-C10 and Rha-Rha-C10-C12 congeners. Further improvement in product concentration and yield through optimization of fermentation conditions and design of various nutrient feeding fed-batch strategies shall be the topic of future investigation.