Polyhydroxyalkanoates Production from Cacao Fruit Liquid Residues Using a Native Bacillus megaterium Strain: Preliminary Study

Abstract

Cacao mucilage exudates (CMEs), byproducts of cacao beans fermentation, are effluents rich in sugars and low-molecular-weight organic acids. In this study, we utilized CMEs to formulate culture media for the biosynthesis of polyhydroxyalkanoates (PHAs) using a native Bacillus megaterium strain (B2). Our investigation followed the adaptation process of B2 to the CMEs-based media, and we closely monitored the development of the microorganism in terms of consumption of acids and sugars. Upon successful adaptation to the CMEs-based media, we transferred the strain to a 4-L batch bioreactor to evaluate the impact of operational variables on PHAs production. We examined the microorganisms’ yield, productivity, and growth kinetics using the CME-based media. Our results showed a product yield of 0.98 g PHA/g carbon source, with an accumulation percentage of 57% and a productivity increase of 33% compared to PHA produced from residual glycerol using the same microorganism. The biopolymer's structure was confirmed to be of a polyhydroxybutyrate homopolymer (PHB) type using various molecular characterization techniques, including Matrix-Assisted Laser Desorption/Ionization mass spectrometry (MALDI-TOF-MS), infrared spectroscopy (IR), elemental composition (EC), ultraviolet–visible spectroscopy (UV–VIS), and thermal analysis (TGA, DSC). Graphical Abstract: (Figure presented.)