Optimization of Fermentation Factors for Polyhydroxybutyrate (PHB) Production Using Bacillus megaterium PNCM 1890 in Simulated Glucose-Xylose Hydrolysates from Agricultural Residues

Abstract

The polyhydroxybutyrate (PHB) production performance of Bacillus megaterium PNCM 1890 in multiple carbon sources was assessed in a model system of simulated glucose-xylose hydrolysates from several agricultural residues (corn stover, sugarcane bagasse, and banana pseudostem). Factors investigated were the type of nitrogen source, carbon-to-nitrogen (C/N) ratio, carbon-to-phosphorus (C/P) ratio, and amount of trace elements in the fermentation medium. Results show that the type of nitrogen source had a significant effect on bacterial growth and PHB production, with urea as the most preferred nitrogen source. In contrast, the type of simulated hydrolysate had no significant effect on the behavior of the bacteria, implying that the microorganism can potentially utilize hydrolysates from various agricultural residues. However, considering conversion efficiency and operating cost, simulated corn stover hydrolysate was selected as the best carbon source. A fermentation time of 28 h was found sufficient to completely utilize both glucose and xylose from the simulated hydrolysate. PHB was also confirmed as a growth-associated product of the bacteria, with observable patterns of catabolite repression and diauxic growth. Optimum conditions that maximize biomass concentration (7.3 g/L), PHB concentration (3.91 g/L), and substrate consumption (98.77% for glucose; 93.76% for xylose) were 14.3 g/g C/N ratio, 21.4 g/g C/P ratio, and 8 mL of trace elements solution (TES) per L of fermentation medium. Nonetheless, PHB was successfully produced using simulated corn stover hydrolysate and urea as carbon and nitrogen sources, respectively. The study provides baseline information on the use of actual hydrolysate, efficient fermentation, and upscaled production of bioplastics from agricultural residues.

Thorough Investigation of the Effects of Cultivation Factors on Polyhydroalkanoates (PHAs) Production by Cupriavidus necator from Food Waste-Derived Volatile Fatty Acids

“…This trend was also observed for PHA accumulation, where a concentration of 1.5 g/L was obtained, leading to a maximum PHA yield on biomass of around 55-56% in all instances. The recorded impact of urea in this study was not in line with findings in studies by Arumugam [61] and Dañez [62], where remarkable superiority of urea compared with other inorganic and complex nitrogen sources was reported for PHA accumulation. The presence of urea, on the other hand, is preferable for bacterial assimilation due to its being a small, polar and uncharged organic molecule.…”

“…Hydrolysates of cheese whey, chicken feather or silage juice were also studied to provide an alternative to more expensive complex nitrogen [58][59][60]. Urea, in most studies, has shown considerable support for both bacterial growth and PHA biosynthesis, substantially increasing PHA accumulation [61][62][63][64]. However, the main carbon sources used in those studies were common sugars of glucose, fructose and oil-based wastes, while information on the utilisation of VFA mixtures is scarce.…”

Effects of different sodium salts and nitrogen sources on the production of 3-hydroxybutyrate and polyhydroxybutyrate by Burkholderia cepacia

“…It might be because the composition in yeast extract is more easily taken up and utilized by B. cepacia cells. Urea is a type of organic nitrogen source with a smaller molecular size and stronger polarity, which can be efficiently used by cells (Dañez et al 2020 ). Therefore, it can be also regarded as a suitable single nitrogen source for 3-HB and PHB production.…”

Production of Polyhydroxyalkanoates by Bacillus megaterium: Prospecting on Rice Hull and Residual Glycerol Potential

“…The production of microbial biopolymers is even more interesting when an alternative culture medium is used, for instance, agro-industrial wastes such as rice hull, wheat straw, sunflower seed hulls, cassava wastewater, and sugar cane bagasse, among others [6]. According to Dañez et al (2020) [7], the use of corn straw, sugarcane bagasse, and banana pseudo-steam have equivalent potential to be used as alternative sources of substrate for polyhydroxybutyrate (PHB) production by Bacillus megaterium.…”