Production of polyhydroxyalkanoates (PHAs) by Bacillus megaterium using food waste acidogenic fermentation-derived volatile fatty acids

Abstract

High production costs still hamper fast expansion of commercial production of polyhydroxyalkanoates (PHAs). This problem is greatly related to the cultivation medium which accounts for up to 50% of the whole process costs. The aim of this research work was to evaluate the potential of using volatile fatty acids (VFAs), derived from acidogenic fermentation of food waste, as inexpensive carbon sources for the production of PHAs through bacterial cultivation. Bacillus megaterium could assimilate glucose, acetic acid, butyric acid, and caproic acid as single carbon sources in synthetic medium with maximum PHAs production yields of 9-11%, on a cell dry weight basis. Single carbon sources were then replaced by a mixture of synthetic VFAs and by a VFAs-rich stream from the acidogenic fermentation of food waste. After 72 h of cultivation, the VFAs were almost fully consumed by the bacterium in both media and PHAs production yields of 9-10%, on cell dry weight basis, were obtained. The usage of VFAs mixture was found to be beneficial for the bacterial growth that tackled the inhibition of propionic acid, iso-butyric acid, and valeric acid when these volatile fatty acids were used as single carbon sources. The extracted PHAs were revealed to be polyhydroxybutyrate (PHB) by characterization methods of Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The obtained results proved the possibility of using VFAs from acidogenic fermentation of food waste as a cheap substrate to reduce the cost of PHAs production.

Polyhydroxyalkanoates production from short and medium chain carboxylic acids by Paracoccus homiensis

“…It could be presumed that the above mentioned factors might have affected achievement of higher PHA concentration. However, the obtained PHA content was about twofold higher than that reported by Vu et al 16 who cultivated Bacillus megaterium also on the CAs-rich stream from the acidogenic fermentation of food waste. To improve the PHA yields, CAs feeding adjustment, optimization of oxygen, pH control is needed.…”

“…To the best of our knowledge, only in a few publications the potential of microorganisms to convert CAs-rich streams from MCF using organic wastes into value-added PHAs was evaluated 13 – 16 . None of this study evaluated in details properties of the extracted biopolyesters.…”

Polyhydroxyalkanoates (PHAs) Production from Volatile Fatty Acids (VFAs) from Organic Wastes by Pseudomonas oleovorans

“…Minimal salt medium (MSM) used in this study was prepared according to [23], with the following composition (in g/L): Na 2 HPO The vitamin solution (added at 1 mL/L) contained 0.05 g/L of d-biotin, 0.2 g/L of paminobenzoic acid, 1 g/L of nicotinic acid, 1 g/L of Ca-pantothenate, 1 g/L of pyridoxine, 1 g/L of thiamine, and 25 g/L of m-inositol, while the trace metal solution (added at 1 mL/L) contained 3 g/L of EDTA,0.9 g/L of CaCl 2 •H 2 O, 0.9 g/L of ZnSO O, and 0.002 g/L of KI [23]. Glucose and synthetic VFAs (SVFAs) media were prepared separately and tested as the sole sources of carbon for cultivation.…”

Bacterial Isolates from Decomposing Rice Straw used for Polyhydroxyalkanoate Production from Straw Hydrolysate Obtained by Alkaline Pretreatment and Enzymatic Hydrolysis

“…The PHA content was also highest in the B. cereus strains, 59.3 wt% in VK92, followed by 46.4 wt% in VK98 (Fig. 3B) and 43.8 wt% in VK 91 ( 4), which may suggest that these isolates are able to utilize the acids and transform them to other metabolic products or perhaps even to PHA (Vu et al 2021). This needs however to be further investigated.…”