44D-2 |
Application of response surface methodology to the study of the growth of a pigment producing microorganism |
A. M. MARTIN, Dept. of Biochemistry, Memorial Univ. of Newfoundland, St. John's, NF A1B 3X9, Canada and M. Sivagurunathan, Environmental Science Program, Memorial Univ. of Newfoundland, St. John's, NF A1B 3X9, Canada. New sources of natural pigments are important to the food industry. Among the microorganisms able to synthesize pigments, the yeast Phaffia rhodozyma has been studied due its uniqueness in the production of astaxanthin, a carotenoid with applications in the aquaculture industry. Studies conducted on this yeast have given priority to the optimization of the pigment production, however the fact that the yeast biomass itself can also be a source of protein and other nutrients for cultivated fish is often ignored when research is done to develop a suitable fermentation process for P. rhodozyma. The main objective of this work was to apply response surface methodology (RSM) techniques to study the effect of the operating parameters on the production of the yeast P. rhodozyma as a microbial biomass protein source and to optimize its production in a fermentation process. Batch fermentation processes were conducted in 250 mL flasks placed in a water batch with controls for agitation, pH and temperature. The culture medium consisted of yeast extract-malt extract broth. The experimental design followed for the RSM experiments was a face-centered cube design, with all the experiments carried out in triplicates. Analyses of the biomass growth were conducted by standard procedures. The results were subjected to a second order multiple regression analysis to obtain the parameters of the mathematical model for the dependent variable biomass concentration. The independent variables studied were fermentation time, temperature and pH. The determination coefficient (R) value for the experiments was 0.96, which indicates that the second order model corresponded well to the experimental results. The maximum experimental value of yeast biomass concentration produced was of approximately 7.5 g/L. The results demonstrate the ability of the mathematical model developed to predict the growth of the biomass of P. rhodozyma under optimized operating conditions. The findings will contribute to the design of an appropriate fermentation process for the production of this yeast as a microbial biomass protein source.
Session 44D, International
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