Abstract
Burkholderia sacchari LMG19450, a non-model organism and a promising microbial platform, was studied to determine nutrient limitation impact on poly(3-hydroxybutyrate) [P(3HB)] production and bacterial growth from xylose, a major hemicellulosic residue. Nitrogen and phosphorus limitations have been studied in a number of cases to enhance PHA accumulation, but not combining xylose and B. sacchari. Within this strategy, it was sought to understand how to control PHA production and even modulate monomer composition. Nitrogen-limited and phosphorus-limited fed-batch experiments in bioreactors were performed to evaluate each one's influence on cell growth and poly(3-hydroxybutyrate) production. The mineral medium composition was defined based on yields calculated from typical results so that nitrogen was available during phosphorus limitation and residual phosphorus was available when limiting nitrogen. Sets of experiments were performed so as to promote cell growth in the first stage (supplied with initial xylose 15 g/L), followed by an accumulation phase, where N or P was the limiting nutrient when xylose was fed in pulses to avoid concentrations lower than 5 g/L. N-limited fed-batch specific cell growth (around 0.19 1/h) and substrate consumption (around 0.24 1/h) rates were higher when compared to phosphorus-limited ones. Xylose to PHA yield was similar in both conditions [0.37 gP(3HB)/gxyl]. We also described pst gene cluster in B. sacchari, responsible for high-affinity phosphate uptake. Obtained phosphorus to biomass yields might evidence polyphosphate accumulation. Results were compared with studies with B. sacchari and other PHA-producing microorganisms. Since it is the first report of the mentioned kinetic parameters for LMG 19450 growing on xylose solely, our results open exciting perspectives to develop an efficient bioprocess strategy with increased P(3HB) production from xylose or xylose-rich substrates.
Highlights
Polyhydroxyalkanoates (PHA) are biopolyesters naturally produced and accumulated as intracellular granules by many Eubacteria and Archaea strains under unbalanced growth conditions (Lee, 1996; Koller et al, 2017)
Considered as biocompatible and fully biodegradable (Keshavarz and Roy, 2010), these biopolymers are proposed as a valuable biomaterial presenting promising biomedical applications (Zhang et al, 2018)
Higher μmax were observed under nitrogenlimiting conditions, indicating that an increased phosphorus concentration is a defining factor to achieve higher growth rates on xylose
Summary
Polyhydroxyalkanoates (PHA) are biopolyesters naturally produced and accumulated as intracellular granules by many Eubacteria and Archaea strains under unbalanced growth conditions (Lee, 1996; Koller et al, 2017). Considered as biocompatible and fully biodegradable (Keshavarz and Roy, 2010), these biopolymers are proposed as a valuable biomaterial presenting promising biomedical applications (Zhang et al, 2018). It has interesting characteristics, PHA production is still too expensive due to the prices of carbon sources, which represents up to 50% of the final production costs (Choi and Lee, 1997). The second most abundant sugar in nature (Lachke, 2002), emerges as an exciting agricultural by-product to be explored as an inexpensive carbon source to produce PHA (Silva et al, 2014; Jiang et al, 2016). If submitted to an efficient hydrolysis treatment, as described by Paiva et al (2009), this amount of bagasse would represent up to 430 × 105 tons of xylose available to be converted into value-added bioproducts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
