title: Retention and regeneration of native NAD(H) in noncharged ultrafiltration membrane reactors: application to L-lactate and gluconate production.
abstract: NAD(H) was retained in a noncharged ultrafiltration membrane reactor for the simultaneous and continuous production of L-lactate and gluconate with coenzyme regeneration. Polyethyleneimine (PEI), a 50-kDa cationic polymer, achieved coenzyme retentions above 0.8 for PEI/NAD(H) molar ratios higher than 5. The ionic strength of the inlet medium caused a decrease of NAD(H) retention that can be counterbalanced by an initial addition of 1% bovine serum albumin (BSA). Continuous reactor performance in the presence of PEI and BSA showed that NAD(H), glucose dehydrogenase, and lactate dehydrogenase were retained by 10-kDa ultrafiltration membranes; L-lactate and gluconate were produced at conversions higher than 95%. PEI enhanced the thermal stability of the enzymes used and increased the catalytic efficiency of glucose dehydrogenase, while no effect was found on the kinetic parameters of lactate dehydrogenase. A model that implements the kinetic equations of the two enzymes describes the reactor behavior satisfactorily. In brief, the use of PEI to retain NAD(H) is a new interesting approach to be widely applied in continuous synthesis with the large number of known dehydrogenases.
authors: Departamento de Bioquímica y Biología Molecular B e Inmunología, Facultad de Química, Universidad de Murcia, Apdo. Correos 4021, 30001, Murcia, Spain.
authors: J M
authors: JM
authors: Obón
authors: A
authors: A
authors: Manjón
authors: J L
authors: JL
authors: Iborra
mesh_terms: D019149:Bioreactors; D001709:Biotechnology / Q000379:methods; D004795:Enzyme Stability / Q000187:drug effects; D005942:Gluconates / Q000378:metabolism*; D042843:Glucose 1-Dehydrogenase; D005948:Glucose Dehydrogenases / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D019344:Lactic Acid / Q000096:biosynthesis*; D008566:Membranes; D008954:Models, Biological; D009243:NAD / Q000737:chemistry / Q000378:metabolism*; D011094:Polyethyleneimine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D014462:Ultrafiltration / Q000379:methods*
chemical_list: D005942:Gluconates; D009243:NAD; D019344:Lactic Acid; D011094:Polyethyleneimine; D005948:Glucose Dehydrogenases; D007770:L-Lactate Dehydrogenase; D042843:Glucose 1-Dehydrogenase; C030691:gluconic acid