title: Bio-based 3-hydroxypropionic- and acrylic acid production from biodiesel glycerol via integrated microbial and chemical catalysis.
abstract: BACKGROUND
  3-Hydroxypropionic acid (3HP) and acrylic acid (AA) are industrially important platform- and secondary chemical, respectively. Their production from renewable resources by environment-friendly processes is desirable. In the present study, both chemicals were almost quantitatively produced from biodiesel-derived glycerol by an integrated process involving microbial and chemical catalysis.
  
  
  RESULTS
  Glycerol was initially converted in a fed-batch mode of operation to equimolar quantities of 3HP and 1,3-propanediol (1,3PDO) under anaerobic conditions using resting cells of Lactobacillus reuteri as a biocatalyst. The feeding rate of glycerol was controlled at 62.5 mg/g(CDW).h which is half the maximum metabolic flux of glycerol to 3HP and 1,3PDO through the L. reuteri propanediol-utilization (pdu) pathway to prevent accumulation of the inhibitory intermediate, 3-hydroxypronionaldehyde (3HPA). Subsequently, the cell-free supernatant containing the mixture of 3HP and 1,3PDO was subjected to selective oxidation under aerobic conditions using resting cells of Gluconobacter oxydans where 1,3PDO was quantitatively converted to 3HP in a batch system. The optimum conditions for the bioconversion were 10 g/L substrate and 5.2 g/L cell dry weight. Higher substrate concentrations led to enzyme inhibition and incomplete conversion. The resulting solution of 3HP was dehydrated to AA over titanium dioxide (TiO2) at 230 °C with a yield of >95%.
  
  
  CONCLUSIONS
  The present study represents the first report on an integrated process for production of acrylic acid at high purity and -yield from glycerol through 3HP as intermediate without any purification step. The proposed process could have potential for industrial production of 3HP and AA after further optimization. Graphical abstract Integrated three-step process for conversion of biodiesel glycerol to 3-hydroxypropionic acid (3HP) and acrylic acid (AA). Glycerol was initially converted to equimolar quantities of 3HP and 1,3-propanediol (1,3PDO) using resting cells of Lactobacillus reuteri. Subsequently, the cell-free supernatant containing the mixture of 3HP and 1,3PDO was subjected to selective oxidation using resting cells of Gluconobacter oxydans where 1,3PDO was quantitatively converted to 3HP. The resulting solution of 3HP was dehydrated to AA over titanium dioxide (TiO2) at 230 °C.
authors.affiliation: Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, 221 00, Lund, Sweden. Tarek.Dishisha@biotek.lu.se.|Department of Microbiology and Immunology, Faculty of Pharmacy, Beni-Suef University, 62511, Beni-Suef, Egypt. Tarek.Dishisha@biotek.lu.se.
authors.forename: Tarek
authors.initials: T
authors.lastname: Dishisha
authors.affiliation: Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, 221 00, Lund, Sweden. Sang-Hyun.Pyo@biotek.lu.se.
authors.forename: Sang-Hyun
authors.initials: SH
authors.lastname: Pyo
authors.affiliation: Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, 221 00, Lund, Sweden. Rajni.Hatti-Kaul@biotek.lu.se.
authors.forename: Rajni
authors.initials: R
authors.lastname: Hatti-Kaul
mesh_terms: D000179:Acrylates / Q000378:metabolism*; D002384:Catalysis; D005990:Glycerol / Q000378:metabolism*; D019344:Lactic Acid / Q000031:analogs & derivatives; D060847:Metabolic Engineering
chemical_list: D000179:Acrylates; D019344:Lactic Acid; C031601:hydracrylic acid; C036658:acrylic acid; D005990:Glycerol