Production of polyhydroxyalkanoates by halotolerant bacteria with volatile fatty acids from food waste as carbon source.

In this study, a halotolerant strain was isolated from high salinity leachate and identified as Bacillus cereus NT-3. It can produce a high concentration of polyhydroxyalkanoates (PHAs) with no significant changes when NaCl concentration is up to 50 g/L. FTIR and NMR spectra of PHAs synthesized by Bacillus cereus NT-3 were similar to the standard or previous results. Effluent from acidogenic fermentation of food waste and pure volatile fatty acids (VFAs) mixture was used as carbon source to check the effect of non-VFAs compounds of the effluent on PHAs production. The maximum PHAs production was 0.42 g/L for effluent fermentation, whereas it was 0.34 g/L for pure VFAs fermentation, indicating that bacteria could use actual effluent in a better way. Furthermore, a mathematical model was established for describing kinetic behavior of bacteria using different carbon sources. These results provided a promising approach for PHAs biosynthesis with a low-cost carbon source.

Metabolomic insights into polyhydroxyalkanoates production by halophilic bacteria with acetic acid as carbon source.

A metabolomics method was established to analyze changes of intracellular metabolites and study the mechanism for enhancing polyhydroxyalkanoates production by halotolerant bacteria, Bacillus cereus strain HY-3, using acetic acid as carbon source. Maximum poly(3-hydroxybutyrate) (PHB) contents for the medium with 0.5 g/L and 5.0 g/L of acetic acid were 41.0 ± 0.415% and 49.2 ± 1.21%. Principal components analysis revealed clear metabolic differences in different growth stages and different concentrations of carbon source. According to statistical analysis, 3-hydroxybutyrate (3-HB), serine, threonine, malate, and pyruvate were determined as potential biomarkers for PHB production. Moreover, metabolic pathways analysis indicated that high level of 3-HB in death phase was due to the limitation of carbon source. Metabolism of glycine, serine, and threonine was influential pathway for PHB production among amino acid metabolisms. High levels of organic acids from the TCA cycle could stimulate the carbon source flux into PHB biosynthetic pathway.