title: An improved screening method for microorganisms able to convert crude glycerol to 1,3-propanediol and to tolerate high product concentrations.
abstract: A new screening method was developed and established to find high-performance bacteria for the conversion of crude glycerol to 1,3-propanediol. Three soil samples from palm oil-rich habitats were investigated using crude glycerol of a German biodiesel plant. Nine promising 1,3-propanediol producers could be found. Because of a special pH buffer system, a fast evaluation on microscale and high 1,3-propanediol concentrations up to 40 g L⁻¹ could be achieved. Three strains demonstrated very high product tolerance and were identified as Clostridium butyricum. Two strains, AKR91b and AKR102a, grew and produced 1,3-propanediol in the presence of 60 g L⁻¹ initial 1,3-propanediol, the strain AKR92a even in the presence of 77 g L⁻¹ 1,3-propanediol. The strains AKR91b and AKR102a tolerated up to 150 g L⁻¹ crude glycerol and produced 80% of the 1,3-propanediol attained from pure glycerol of the same concentration. Further criteria for the choice of a production strain were the pathogenicity (risk class), ability to grow on low-cost media, e.g., with less yeast extract, and robustness, e.g., process stability after several bioconversions. Overall, the strain C. butyricum AKR102a was chosen for further process optimization and scale-up due to its high productivity and high final concentration in a pH-regulated bioreactor.
authors.affiliation: Johann Heinrich von Thünen-Institut (vTI), Institute of Agricultural Technology and Biosystems Engineering (AB), Bundesallee 50, 38116 Braunschweig, Germany.
authors.forename: Anne Katrin
authors.initials: AK
authors.lastname: Ringel
authors.forename: Erik
authors.initials: E
authors.lastname: Wilkens
authors.forename: Diana
authors.initials: D
authors.lastname: Hortig
authors.forename: Thomas
authors.initials: T
authors.lastname: Willke
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Vorlop
mesh_terms: D056804:Biofuels; D019149:Bioreactors; D001709:Biotechnology / Q000379:methods; D046972:Clostridium butyricum / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism*; D003470:Culture Media; D005990:Glycerol / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D000073878:Palm Oil; D010938:Plant Oils; D011409:Propylene Glycols / Q000378:metabolism* / Q000494:pharmacology; D012988:Soil Microbiology
chemical_list: D056804:Biofuels; D003470:Culture Media; D010938:Plant Oils; D011409:Propylene Glycols; C041787:1,3-propanediol; D000073878:Palm Oil; D005990:Glycerol