PHB Biosynthesis in Catabolite Repression Mutant of Burkholderia sacchari

Abstract

Due to the effect of catabolite repression, sugar mixtures cannot be metabolized in a rapid and efficient way implicating in lower productivity in bioprocesses using lignocellulosic hydrolysates. In gram-negative bacteria, this mechanism is mediated by the phosphotransferase system (PTS), which concomitantly internalizes and phosphorylates sugars. In this study, we isolated a UV mutant of Burkholderia sacchari, called LFM828, which transports hexoses and pentoses by a non-PTS uptake system. This mutant presented released glucose catabolite repression over the pentoses. In mixtures of glucose, xylose, and arabinose, specific growth rates and the specific sugar consumption rates were, respectively, 10 and 23% higher in LFM828, resulting in a reduced time to exhaust all sugars in the medium. However, in polyhydroxybutyrate (PHB) biosynthesis experiments it was necessary the supplementation of yeast extract to maintain higher values of growth rate and sugar consumption rate. The deficient growth in mineral medium was partially recovered by replacing the ammonium nitrogen source by glutamate. It was demonstrated that the ammonium metabolism is not defective in LFM828, differently from ammonium, glutamate can also be used as carbon and energy allowing an improvement on the carbohydrates utilization for PHB production in LFM828. In contrast, higher rates of ammonia consumption and CO(2) production in LFM828 indicate altered fluxes through the central metabolism in LFM828 and the parental. In conclusion, PTS plays an important role in cell physiology and the elimination of its components has a significant impact on catabolite repression, carbon flux distribution, and PHB biosynthesis in B. sacchari.

Use of Lignocellulosic Materials for PHA Production

“…In some bacterial strains, CCR is mediated by proteins of the phospho-transferase system (PTS bon up-take in sugar mixtures. The wild strain only started consuming xylose after glucose was completely depleted, while one UV mutant was able to consume glucose and xylose simultaneously 36 . Generally, the rate of feeding during fed-batch cultivation should be controlled to overcome accumulation of slowly assimilated sugars in medium.…”

Exploring the potential of Burkholderia sacchari to produce polyhydroxyalkanoates

“…; Lopes et al . , ). In this work, 30 different carbon sources were supplied as cosubstrates to B. sacchari along with glucose to evaluate the potential of this bacterium to incorporate comonomers into PHA.…”

“…This bacterium accumulates up to 75% of cell dry weight (CDW) as PHA (Gomez et al 1996). Burkholderia sacchari is a promising industrial strain as it can also use xylose as a sole carbon source and even hemicellulosic hydrolysates from sugarcane bagasse (Silva et al 2004;Lopes et al 2009Lopes et al , 2011. In this work, 30 different carbon sources were supplied as cosubstrates to B. sacchari along with glucose to evaluate the potential of this bacterium to incorporate comonomers into PHA.…”

Utilization of biodiesel-derived glycerol or xylose for increased growth and lipid production by indigenous microalgae

“…However, these processes are highly dependent on the purity of the waste stream and face several challenges before being scaled up. Biological approaches being developed include production of PHB (polyhydroxybutyrate), a feedstock for the production of bioplastics (Garcez Lopes et al 2011); and biofuels, such as ethanol, isobutanol and triacylglycerol (TAG) (Brat & Boles 2013;Kurosawa et al 2013;Q. Li et al 2008).…”