Production of PHB from Crude Glycerol

Abstract

Crude glycerol – a by‐product of the large scale production of diesel oil from rape – is examined for its possible use as a cheap feedstock for the biotechnological synthesis of poly(3‐hydroxybutyrate) (PHB). The glycerol samples of various manufacturers differ in their contamination with salts (NaCl or K2SO4), methanol or fatty acids. At high cell density fermentation these pollutants could possibly accumulate to inhibiting concentrations. The bacteria used were Paracoccus denitrificans and Cupriavidus necator JMP 134, which accumulate PHB from pure glycerol to a content of 70 % of cell dry mass. When using crude glycerol containing 5.5 % NaCl, a reduced PHB content of 48 % was observed at a bacterial dry mass of 50 g/L. Furthermore the PHB yield coefficient was reduced, obviously due to osmoregulation. The effect of glycerol contaminated with K2SO4 was less pronounced. The molecular weight of PHB produced with P. denitrificans or C. necator from crude glycerol varies between 620000 and 750000 g/mol which allows the processing by common techniques of the polymer industry.

Production and characterization of poly-3-hydroxybutyrate from crude glycerol by Bacillus sphaericus NII 0838 and improving its thermal properties by blending with other polymers

“…Its utilization in biodegradable polymer production will be attractive. The utilization of crude glycerol from biodiesel industry has been reported by several authors (Ashby et al, 2004;Borman and Roth, 1999;Koller et al, 2005;Mothes et al, 2007). However, significant decrease in PHB productivity and yields were reported.…”

Production of biopolyester poly(3-hydroxybutyrate) by Bacillus cereus RCL 02, a leaf endophyte of Ricinus communis L.

“…Development of newer fermentation strategies along with use of nonconventional renewable carbon sources including different plant oils [17,18], molasses [19], oil cake extracts [20], crude glycerol [21] and agricultural wastes [22] have been explored to reduce the cost of PHAs production and making the process economically viable.…”

Microbial community engineering for biopolymer production from glycerol

“…However, it was the methanol fraction present in the fed stream which was utilized as primary carbon source while glycerol was not consumed according to their results. Nevertheless, the main body of research conducted on the use of crude glycerol as substrate for PHA production reports the preferable use of glycerol compared to methanol (Ashby et al 2004;Bormann and Roth 1999;Cavalheiro et al 2009;Koller et al 2005;Mothes et al 2007;Zhu et al 2010). According to these studies, it would be likely the case that the glycerol fraction will be used for PHB synthesis instead of methanol.…”

“…Also during bioethanol production, a glycerol containing waste stream is generated. The glycerol weight percentage in crude glycerol depends on the biodiesel manufacturing process and varies between 62 and 90 wt.% (González-Pajuelo et al 2005;Mothes et al 2007; Thompson and He 2006). Considering that biodiesel production generates 10 wt.% crude glycerol (Johnson and Taconi 2007), the amount of crude glycerol produced in Europe in 2009 amounts approximately 900 ktons (European Biodiesel Board, 2011, http://www.ebb-eu.org/stats.php).…”