Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-V-21All experiments were conducted at previously defined optimal process conditions (Goršekand Tramšek, 2007). On the basis of experimental data of time-depended kefir grain massincrease growth parameters in Gompertz predictive growth model were determined.Simultaneously, during individual experiments at different batch propagation times the pHvalues of fermentation medium were dynamically measured. Experimental dynamic pHprofiles were mathematically analyzed and the values of shape parameters of the supposedexponential pH model were determined. In the second part of the study, we estimated theoptimal volumes of a five in series connected CSTRs for desired capacity of kefir grainsproduction, q m,KG,pr = 3 kg/h and final conversion, X o,N = 0,98 by implementing NLPoptimization problem using high-level modeling system GAMS (Rosenthal, 2006). At thesame time the total reactor volume of five-stage system was compared with the potentialreactor volume if only one CSTR is considered.With our analysis it has been verified that multi-stage continuous reactor systemcompared to the one-stage one is technologically and economically much more reasonable,because its total volume is more than twelve times lower. We also proved the importance ofproper multi-stage bioreactor system design using NLP methodology.References1. Athanasiadis I, Boskou D, Kanellaki M and Koutinas AA, Effect of carbohydrate substrate on fermentationby kefir yeast supported on delignified cellulosic materials. J Agr Food Chem 49: 658-663 (2001).2. Athanasiadis I, Paraskevopoulou A, Blekas G and Kiosseoglou V, Development of a novel whey beverageby fermentation with kefir granules. Effect of various treatments. Biotechnol Prog 20: 1091–1095 (2004).3. Goršek A and Tramšek M, Quantitative examination of process parameters during kefir grain biomassproduction. Int J Chem Reactor Eng 5: S8 (2007).4. Plessas S, Pherson L, Bekatorou A, Nigam P and Koutinas AA, Bread making using kefir grains as baker'syeast. Food Chem 93: 585-589 (2005).5. Rimada PS and Abraham AG, Polysaccharide production by kefir grains during whey fermentation. J DairyRes 68: 653-661 (2001).6. Rosenthal RE, GAMS – A users’s quide, GAMS Development Corporation, Washington, (2006).7. Williams JA, Keys to bioreactor selections, Chem Eng Prog, 98: 34–41 (2002).209