title: Dipeptide synthesis and separation in a reversed micellar membrane reactor.
abstract: The synthesis of dipeptide AcPheLeuNH2 catalyzed by alpha-chymotrypsin encapsulated in TTAB/octanol/heptane reversed micelles was investigated in a tubular ceramic membrane reactor, operated in a batch mode. The reaction medium conditions (TTAB concentration, buffer molarity, and pH) were optimized using a factorial design in order to achieve maximum synthesis rates. Hydrated reversed micelles permeated through the membrane together with the substrate ester, dipeptide, and by-products. However, as a result of the low solubility of the peptide in the reaction medium, selective precipitation occurred, thus enabling the complete retention of the solid product by the ultrafiltration membrane and therefore an integration of a separation step in the biotransformation process. In spite of the continuous accumulation of solids inside the reactor, constant permeation flow rates could be maintained throughout the operation. The influence of alpha-chymotrypsin, TTAB, and water concentration on the kinetics and mass transfer of the system was also investigated. The behavior of the system during a continuous experiment was also evaluated.
authors.affiliation: Laboratório de Engenharia Bioquímica, Instituto Superior Técnico, Lisboa, Portugal.
authors.forename: M L
authors.initials: ML
authors.lastname: Serralheiro
authors.forename: D M
authors.initials: DM
authors.lastname: Prazeres
authors.forename: J M
authors.initials: JM
authors.lastname: Cabral
mesh_terms: D001709:Biotechnology; D002021:Buffers; D002918:Chymotrypsin / Q000378:metabolism; D004151:Dipeptides / Q000096:biosynthesis* / Q000138:chemical synthesis* / Q000302:isolation & purification*; D004951:Esterification; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D008567:Membranes, Artificial; D008823:Micelles; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; D050337:Trimethyl Ammonium Compounds; D014867:Water
chemical_list: D002021:Buffers; D004151:Dipeptides; D008567:Membranes, Artificial; D008823:Micelles; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; D050337:Trimethyl Ammonium Compounds; C091187:acetylphenylalanyl-leucinamide; D014867:Water; D002918:Chymotrypsin; C009410:tetradecyltrimethylammonium