بررسي آزمايشگاهي فرآيند توليد بيوسورفكتانت سوفوروليپيدي از بخش‌هاي مختلف ضايعات جامد شهري

The rapid increase in food waste, in addition to creating environmental challenges an‎d disposal costs, also offers an opportunity for the production of valuable biobased compounds. This study aimed to investigate the potential of food waste as a sustainable substrate for the production of sophorolipid biosurfactants using Starmerella bombicola. The effects of different pretreatment methods (acidic an‎d organic-solvent) an‎d enzymatic hydrolysis on the release of fermentable sugars an‎d the improvement of production yield were eva‎luated. Food waste was divided into two categories: ethanol-extracted (Soxhlet) an‎d non-extracted. Acid pretreatment was carried out in two stages (120 °C an‎d 150 °C for the first stage, followed by 180 °C for the second stage). The liquid fraction obtained contained free sugars for direct fermentation, while the solid fraction was subjected to enzymatic hydrolysis. The highest amount of released sugar (35 g/L) was observed in the Soxhlet-extracted sample pretreated at 150 °C, which resulted in a fermentation yield of 0.46 g/g. Organic-solvent pretreatment at 120 °C combined with enzymatic hydrolysis (a mixture of cellulolytic an‎d non-cellulolytic enzymes) provided the most favorable conditions, leading to the production of 49.19 g/L biosurfactant with a yield of 0.69 g/g, which is competitive with processes based on pure substrates. In addition, semi-continuous fermentation with in-situ product separation was carried out by daily feeding of glucose an‎d oleic acid under controlled conditions (pH = 3.5, temperature = 30 °C, aeration = 3.5 vvm, agitation = 500 rpm). In-situ separation, applied from day four to day eight by withdrawing the sophorolipid-containing phase an‎d recycling the broth back into the fermenter, reduced product inhibition an‎d improved production efficiency. The maximum sophorolipid production (137 g/L) was achieved on day six, concurrent with the highest cell biomass (88 g/L). The findings demonstrated that the choice of pretreatment type, temperature, an‎d enzyme combination plays a critical role in sugar release an‎d yield improvement. Organic-solvent pretreatment at mild temperature (120 °C) provides an effective an‎d sustainable approach for enhancing biosurfactant production from food waste. These results can contribute to the design of industrial processes an‎d the development of waste-based biotechnological applications.

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