An article in the Electronic Journal of Biotechnology

(“Optimization of Medium Composition for Transglutaminase Production by a Brazilian Soil Streptomyces sp,” available at The correct URL is http://www.ejbiotechnology.info/index.

php/ejbiotechnology/article/viewFile/v10n4-10/110) 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.