Revaluation of agro-industrial waste through Biotechnology: Papaya peel waste as feedstock for PHB production by native Bacillus strains

The environmental impact of synthetic plastics and agro-industrial waste has made it necessary to develop sustainable biopolymer alternatives. This research evaluated the potential of papaya peel waste, an abundant agricultural byproduct in the Santander region, as an alternative carbon source for the synthesis of bioplastics like polyhydroxyalkanoates (PHAs) by bacterial fermentation. The process was carried out in two steps. In the first stage, a central composite design based on response surface methodology was applied to optimize four process variables (carbon source concentration, temperature, pH and inoculum concentration) using Bacillus thuringiensis fermentation cultivated on papaya peel extract. The optimal conditions were identified as a temperature of 31.4 °C, a sugar concentration of 10 g/L, a pH of 5.5 and an inoculum concentration of 4% (v/v). In the second step, a validated fermentation process under these optimized conditions resulted in a maximum PHA accumulation of 81.0±0.85% of cell dry weight. Chemical analysis confirmed that the major biopolymer produced was the homopolymer poly(3-hydroxybutyrate) (PHB). These results demonstrate the potential of valorizing papaya peel waste as sustainable fermentative carbon source to produce high-value biopolymers, promoting the circular economy in Santander and reusing agricultural waste that is usually discarded while contributing to the sustainable management of organic waste in the region.