Synthesis of Polyhydroxybutyrate (PHB) by Fermentation of Whey and Pineapple Peel with Bacillus subtilis

Environmental pollution caused by petroleum-based plastics is a global problem due to the accumulation of waste, microplastic pollution, and greenhouse gas emissions. In this context, bioplastics, such as polyhydroxybutyrate (PHB), emerge as a sustainable alternative, as they are biodegradable and produced from renewable resources. This study evaluated the use of agro-industrial waste from Ecuador, specifically whey and pineapple peel, as carbon sources for the production of PHB through fermentation with Bacillus subtilis. Enzymatic hydrolysis of whey was performed with lactase, obtaining an optimal concentration of 761 ppm of glucose in 2 hours. For pineapple peel, acid hydrolysis with 6% H2SO4 was used, achieving a concentration of 5125.81 mg/L of reducing sugars in 30 minutes. Whey fermentation was carried out at pH 6, 37 °C, and 7 days of incubation, while pineapple peel fermentation was carried out at pH 7.7 and 36.7 °C. Whey fermentation produced a higher PHB yield (0.331 g/L) compared to pineapple peel (0.272 g/L). These results demonstrate the potential of both wastes as economical and sustainable substrates for obtaining PHB, highlighting whey as a more efficient source. This study demonstrates that the use of agro-industrial waste for PHB production through fermentation with Bacillus subtilis is a viable and efficient strategy, highlighting whey as a more effective carbon source compared to pineapple peel, which could have a significant impact on waste reduction and environmental sustainability.