2.17 Yeast culture and astaxanthin production The yeast Phaffia rhodozyma produces the carotenoid pigment astaxanthin in the absence of light. The cells are grown in batch culture using medium, containing 40 g glucose. Cell, substrate, and product concentrations are measured as a function of culture time. The results are as follows. Astaxanthin Cell Concentration Sugar Concentration Concentration Time (h) (gI dry weight) (g1) (mg I) 0.01 0.019 0.029 0.029 0.074 0.124 0.157 0.356 0.906 2.28 3.67 7.17 0 40 39.96 39.90 39.91 39.65 9.14 38.95 38.22 35.24 32.40 17.05 0 0.19 0.32 0.45 0.60 0.72 0.81 0.87 1.01 1.29 1.35 1.33 10 12 20 24 35 70 78 0 (a) Does the culture exhibit a lag phase? (b) Does growth of Phaffia rhodozyma follow first-order kinetics? (c) Evaluate max and the culture doubling time. Over what period are these parameters valid representations of growth? astaxanthin synthesis. Express your answer in units of mg 1 What confidence do you have in this result? (d) From a plot of astaxanthin concentration versus time, estimate the initial rate of h (e) Using the result from (d), estimate the initial specific rate of astaxanthin production.
