Growth of Ca-D-malate crystals in a bioreactor

To develop a bioreactor for solid-to-solid conversions, the conversion of s olid Ca-maleate to solid Ca-D-malate by permeabilized Pseudomonas pseudoalc aligenes was studied. In a bioreactor seeded with product (Ca-D-malate) cry stals, growth of Ca-D-malate crystals is the last step in the solid-to-soli d conversion and is described here. Crystal growth is described as a transp ort process followed by surface processes. In contrast to the linear rate l aw obeyed by the transport process, the surface processes of a crystal-grow th 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 su rface-controlled and obeyed an exponential rate law. Based on this rate law , a kinetic model was developed which describes the decrease in supersatura tion due to Ca-D-malate crystal growth as a function of the constituent ion s, Ca2+ and D-malate(2-). The kinetic parameters depended on temperature, b ut, as expected (surface-controlled), they were hardly affected by the stir ring speed. (C) 2000 John Wiley & Sons, Inc.