Selective Hydrogenolysis of Glycerol and Crude Glycerol (a By-Product or Waste Stream from the Biodiesel Industry) to 1,2-Propanediol over B2O3 Promoted Cu/Al2O3 Catalysts

Biosurfactants are produced by bacteria or yeast utilizing different substrates as sugars, glycerol, or oils. They have important applications in the detergent, oil, and pharmaceutical industries. Glycerol is the product of biodiesel industry and the existing glycerol market cannot accommodate the excess amounts generated; consequently, new markets for refined glycerol need to be developed. The aim of present work is to optimize the production of microbial rhamnolipid using waste glycerol. We have developed a process for the production of rhamnolipid biosurfactants using glycerol as the sole carbon source by a local Pseudomonas aeruginosa isolate that was obtained from an extensive screening program. A factorial design was applied with the goal of optimizing the rhamnolipid production. The highest production yield was obtained after 2 days when cells were grown in minimal salt media at pH 6, containing 1% (v/v) glycerol and 2% (w/v) sodium nitrate as nitrogen source, at 37°C and at 180 rpm, and reached 2.164 g/L after 54 hours (0.04 g/L h). Analysis of the produced rhamnolipids by TLC, HPLC, and FTIR confirmed the nature of the biosurfactant as monorhamnolipid. Glycerol can serve as a source for the production of rhamnolipid from microbial isolates providing a cheap and reliable substrate.

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Exploring nutrient limitation for polyhydroxyalkanoates synthesis by newly isolated strains ofAeromonassp. using biodiesel-derived glycerol as a substrate

PeerJ ◽

10.7717/peerj.5838 ◽

2018 ◽

Vol 6 ◽

pp. e5838 ◽

Cited By ~ 4

Author(s):

Justyna Możejko-Ciesielska ◽

Tomasz Pokoj

Keyword(s):

Crude Glycerol ◽

Municipal Wastewater ◽

Nitrogen Deficiency ◽

Treatment Plant ◽

Second Step ◽

Rrna Gene ◽

Municipal Wastewater Treatment ◽

Nitrogen And Phosphorus ◽

Pure Glycerol ◽

Biodiesel Industry

Aeromonasspp. strains isolated from activated sludge in a municipal wastewater treatment plant were found to be able to synthesize polyhydroxyalkanoates (PHA) utilizing pure and crude glycerol. The 16S rRNA gene sequence of the isolates exhibited similarity toAeromonas hydrophila,A. aquatica, andA. salmonicida. Our results confirmed that the adequate supply of nitrogen and phosphorus during culture in 250-ml shake flasks did not stimulate the synthesis of PHAs. The results indicate that the PHA content of cells was higher under a phosphorus-limiting environment compared to nitrogen starvation. In the two-stage cultivation using glucose (in the first step) and crude glycerol from biodiesel industry (in the second step) as a component of the growth medium, the analyzed strains grew to 3.06 g/l of cell dry weight containing up to 22% of PHAs. Furthermore, during the same culture strategy up to 42% of PHAs were extracted, when in the second step of the process,Aeromonassp. AC_03 was grown on pure glycerol under phosphorus limitation. The purified biopolymer was confirmed to be polyhydroxybutyrate.Aeromonassp. AC_02 was also capable to accumulate the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer when pure glycerol was added as a substrate under nitrogen-deficiency one-step bioprocess. Our results confirm that due to the biopolymer productivity, newly isolated strains could be exploited for obtaining valuable biopolymers using wastes generated from biodiesel industry.

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