508968.fig.004a
(a)
508968.fig.004b
(b)
508968.fig.004c
(c)
508968.fig.004d
(d)
Figure 4: Response surface showing the interaction between five parameters and C/N; (a) sucrose and NaNO3, (b) sucrose and Triton X-100, (c) yeast extract and Zn+2, and (d) NaNO3 and Triton X-100. Other variables are constant at their center points. The numbers inside the contour plots indicate the C/N.