title: Growth of Ca-D-malate crystals in a bioreactor.
abstract: To develop a bioreactor for solid-to-solid conversions, the conversion of solid Ca-maleate to solid Ca-D-malate by permeabilized Pseudomonas pseudoalcaligenes was studied. In a bioreactor seeded with product (Ca-D-malate) crystals, growth of Ca-D-malate crystals is the last step in the solid-to-solid conversion and is described here. Crystal growth is described as a transport process followed by surface processes. In contrast to the linear rate law obeyed by the transport process, the surface processes of a crystal-growth process can also obey a parabolic or exponential rate law. Growth of Ca-D-malate crystals from a supersaturated aqueous solution was found to be surface-controlled and obeyed an exponential rate law. Based on this rate law, a kinetic model was developed which describes the decrease in supersaturation due to Ca-D-malate crystal growth as a function of the constituent ions, Ca(2+) and D-malate(2-). The kinetic parameters depended on temperature, but, as expected (surface-controlled), they were hardly affected by the stirring speed.
authors.affiliation: Wageningen University, Food and Bioprocess Engineering Group, Department of Food Technology and Nutritional Sciences, Biotechnion/Dreijencomplex, P.O. Box 8129 / 6700 EV Wageningen, The Netherlands. MARCO.MICHIELSEN@ALGEMEEN.PK.WAU.NL
authors.forename: M J
authors.initials: MJ
authors.lastname: Michielsen
authors.forename: C
authors.initials: C
authors.lastname: Frielink
authors.forename: R H
authors.initials: RH
authors.lastname: Wijffels
authors.forename: J
authors.initials: J
authors.lastname: Tramper
authors.forename: H H
authors.initials: HH
authors.lastname: Beeftink
mesh_terms: D019149:Bioreactors; D001709:Biotechnology / Q000379:methods*; D002118:Calcium / Q000737:chemistry; D003460:Crystallization; D007700:Kinetics; D008293:Malates / Q000737:chemistry*; D008956:Models, Chemical; D012995:Solubility; D013499:Surface Properties
chemical_list: D008293:Malates; C030298:malic acid; D002118:Calcium