11.37. An article in the Electronic Journal of Biotechnology (“Optimization of Medium Composition for Transglutaminase Production by a Brazilian Soil Streptomyces sp,” available at http://www.ejbiotechnology

.info/content/vol10/issue4/full/10.index.html) describes the use of designed experiments to improve the medium for cells used in a new microbial source of transglutaminase

(MTGase), an enzyme that catalyzes an acyl transfer reaction using peptide-bond glutamine residues as acyl donors and some primary amines as acceptors. Reactions catalyzed by MTGase can be used in food processing. The article describes two phases of experimentation—screening with a fractional factorial and optimization. We will use only the optimization experiment. The design was a central composite design in four factors—x1 $ KH2PO4, x2 $ MgSO4-7H2O, x3 $ soybean flower, and x4 $ peptone. MTGase activity is the response, which should be maximized. Table P11.13 contains the design and the response data.

(a) Fit a second-order model to the MTGase activity response.

(b) Analyze the residuals from this model.

(c) Recommend operating conditions that maximize MTGase activity.

Transcribed Image Text:

Standard Order X1 X2 X3 1 -1 -1 -1 2 1 3 -1 1 -1 4 1 1 56589 -1 -1 1 1 -1 1 -1 1 1 1 1 * X4 MTGase activity -1 0.87 0.74 -1 0.51 0.99 0.67 0.72 0.81 1.01 -1 -1 1 1.33 10 1 -1 1 0.7 11 1 1 -1 1 0.82 12 1 1 -1 1 0.78 13 -1 -1 1 1 0.36 14 1 -1 1 1 0.23 15 1 1 1 1 0.21