title: Efficient malic acid production from glycerol with Ustilago trichophora TZ1.
abstract: BACKGROUND
  The large surplus of crude glycerol, as main low-value waste stream in biodiesel production, has led to the investigation of new possibilities for the production of value-added chemicals from this feedstock. New and efficient (bio-) catalysts are needed that are able to convert glycerol to versatile chemical building blocks. This would contribute to further develop away from a mainly petroleum based, to a sustainable, bio-based industry. One promising group of discussed building block chemicals are dicarbonic acids.
  
  
  RESULTS
  Here, we report the efficient synthesis of malate from glycerol using Ustilago trichophora RK089, which was identified in a screening of 74 Ustilaginaceae. For economically feasible production that can compete with existing processes, a high productivity is required. By adaptive laboratory evolution, the growth and production rate were increased by 2.5- and 6.6-fold, respectively. Further medium optimization increased the final titer, yield, and overall production rate to 196 g L(-1), 0.82 gmal ggly (-1), and 0.39 g L(-1) h(-1), respectively.
  
  
  CONCLUSIONS
  This titer is the highest reported for microbial malate production, making U. trichophora TZ1 a promising microbial production host for malate from crude glycerol, especially since it is not genetically engineered. Since this production process starts from an industrial waste stream as substrate and yields an interesting platform chemical, which can be used to replace petro-chemicals, it greatly contributes to a sustainable bio-economy.
authors.affiliation: Institute of Applied Microbiology-iAMB, Aachen Biology and Biotechnology-ABBt, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
authors.forename: Thiemo
authors.initials: T
authors.lastname: Zambanini
authors.affiliation: Institute of Applied Microbiology-iAMB, Aachen Biology and Biotechnology-ABBt, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
authors.forename: Eda
authors.initials: E
authors.lastname: Sarikaya
authors.affiliation: Institute of Applied Microbiology-iAMB, Aachen Biology and Biotechnology-ABBt, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Kleineberg
authors.affiliation: BRAIN AG, 64673 Zwingenberg, Germany.
authors.forename: Joerg M
authors.initials: JM
authors.lastname: Buescher
authors.affiliation: BRAIN AG, 64673 Zwingenberg, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Meurer
authors.affiliation: Institute of Applied Microbiology-iAMB, Aachen Biology and Biotechnology-ABBt, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
authors.forename: Nick
authors.initials: N
authors.lastname: Wierckx
authors.affiliation: Institute of Applied Microbiology-iAMB, Aachen Biology and Biotechnology-ABBt, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
authors.forename: Lars M
authors.initials: LM
authors.lastname: Blank
keywords: Adaptive laboratory evolution; Glycerol; Malate; Medium optimization; Ustilago trichophora