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

Alkaline-Tolerant Bacillus cereus 12GS: A Promising Polyhydroxybutyrate (PHB) Producer Isolated from the North of Mexico

“…Within the range of 1000 to 1300 cm −1 , a series of pronounced bands signifies the stretching of the (C-O) bond inherent to the ester group. Importantly, all these spectral features align closely with the standard commercial polyhydroxybutirate (Sigma-Aldrich) (Figure 6); therefore, it is confirmed that the polymeric extract studied is a short chain named polyhydroxybutyrate (PHB) [29,62].…”

“…Additionally, the 3,5-dinitrosalicylic acid (DNS) method was employed to measure sugar concentrations throughout the fermentation time [27]. From the experimental data, the following kinetic parameters were calculated to evaluate growth and PHB production behavior [28][29][30].…”

Green Synthesis of Bioplastics from Microalgae: A State-of-the-Art Review

“…For instance, Mozejko-Ciesielska et al [42] reported a highest yield of 0.42 g/L PHA from Halomonas alkaliantarctica using dairy waste as a carbon source. Similarly, Bacillus megaterium was found to secrete 0.98 g PHA/carbon in the presence of cacao fruits residue [43]. In addition, some bacteria, and yeasts (such as Saccharomyces cerevisiae, Candida krusei, Rhodotorula glutinis, Ralstonia eutropha, and Kluyveromyces africans) that utilize polyphosphate complexes in their membrane transport produce low-molecular weight PHB [44,45].…”