536310.fig.004a
(a)
536310.fig.004b
(b)
536310.fig.004c
(c)
536310.fig.004d
(d)
Figure 4: Scanning electron microscopic images of morphological analysis of various pretreatment processes. (a) Control, (b) acid pretreatment, (c) enzyme pretreatment, and (d) ultrasonication.