The main advantage of RSM is to reduce the number of
experimental trials needed to evaluate multiple variables and their
interactions, and provide the information necessary for design and
process optimisation (Wu et al., 2007). In general, it applies an
experimental design, such as central composite design (CCD), to
fit a second order polynomial by a least squares technique. This approach
has been successful for enhancing yields of enzymes in our
laboratory (Puri, Kaur, Barrow, & Singh, 2011) and is thus attempted
in the present study to maximise stevioside yield.