A multiphasic hollow fiber reactor for the whole-cell bioconversion of 2-methyl-1,3-propanediol to (r)-beta-hydroxyisobutyric acid.
This paper describes the bioconversion of 2-methyl-1,3-propanediol to (R)-beta-hydoxyisobutyric acid (HIBA) by Acetobacter ALEI in a hollow fiber membrane bioreaction system arrangement that allows the integration of three liquid phases: the aqueous bioconversion phase, the organic phase consisting of a solution of trioctyl phosphine oxide (TOPO) in isooctane, and the third phase consisting of a basic stripping solution that allows reextraction of HIBA from the organic phase. A comparison of HIBA mass transfer experiments was carried out in the membrane reactor with two and three phases for different pH and TOPO concentrations. The use of the three-phase arrangement allows the extraction of high quantities of HIBA from the aqueous medium (higher than 85%) independently of the pH, whereas in the two-phase system the percentage of HIBA extracted from the aqueous medium was lower, 42% in the best case, and strongly influenced by the pH. The percentage of the extractive agent TOPO in the organic phase influenced on the mass transfer rate in both bi- and triphasic arrangements. By simply integrating the re-extraction phase in the system it was possible to increase the extraction yield by 2-fold, reduce the amount of TOPO by 4-fold, and operate at the more favorable pH 4. A bioconversion experiment was done in these conditions (pH = 4, TOPO = 5%) to confirm the advantages of including the third stripping solution. Fed-batch operation of the triphasic membrane reactor was maintained for more than 20 h, reaching an HIBA concentration in the stripping solution of 29 g L(-)(1).
León
R
R
Departamento de Química y Ciencias de los Materiales, Escuela Politécnica Superior, Campus de la Rábida, Universidad de Huelva, 21819-Huelva, Spain. rleon@uhu.es
Prazeres
D M
DM
Fernandes
P
P
Molinari
F
F
Cabral
J M
JM
D000091:Acetobacter / Q000378:metabolism*; D019149:Bioreactors; D004867:Equipment Design; D006885:Hydroxybutyrates / Q000378:metabolism*; D007218:Industrial Microbiology / Q000295:instrumentation* / Q000379:methods; D011409:Propylene Glycols / Q000378:metabolism*
D006885:Hydroxybutyrates; D011409:Propylene Glycols; C020757:3-hydroxyisobutyric acid; C437090:2-methyl-1,3-propanediol