Applicability of the Three Dimensional Growth Model in Description of Mucor miehei NCAIM 5238 Cultivation and Renin Biosynthesis

S. Matošić, Ž. Kurtanjek, M. Bošnjak and B. Šlaus

Abstract
Fungus Mucor miehei NCAIM 5238 during its growth in complex nutritive media effectively produces proteolytic enzymes, which besides hydrolitic also exhibit coagulation effects. Therefore, it is applied in industrial production of complex enzymatic preparation (renin), which is used in cheese production. The kinetics of microorganism growth and renin production were studied in a pilot-plant bioreactor of 1200 L working volume. During the batch culture the microorganism was growing in filaments and pellets, the later becoming predominant at the end of batch culture. The present work is based on experimental evidence, which indicates that the process kinetics in general could be roughly described by applying a simple mathematical model based on the three dimensional growth concept. The applicability of the model with respect to biomass growth, substrate uptake, oxygen transfer and uptake as well as the product formation kinetics was investigated. The batch culture range after 10 hours of the apparent lag phase was subjected to the study with respect to the mathematical model application. Application of the minimum variance method yielded kinetic parameters which gave a close fit between experimental and simulated data (coefficients of determination are R2x = 0.985; R2s = 0.995; R2DO = 0.981; R2P = 0.975). Computer simulation of the combination of batch and fed batch operations indicated a possible increase in renin production up to 30 %.

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Keywords
Renin, Mucor miehei, mathematical modeling