3.3. Biodiesel production by MPPB
The influences of single and interactive variables on biodiesel
production by MPPB were studied. The results of DoEs are presented in Table 4. Main effect plots of single variables and relative
influences of all variables are shown in Fig. 4.
Biodiesel yield was increased significantly by such single variables as alcohol:oil ratio (X12), substrate flow (X10), reaction temperature (X11), and total reaction time (X14) (Fig. 4). However,
increased amount of water (X13) had insignificant effect on the
biodiesel yield. The important two-way interactions affecting biodiesel yield were substrate flow–alcohol:oil (X10X12) and substrate flow–total reaction time (X10X14). Different methanol to
oil ratios (4:1–6:1) were studied. It was found that an increase in
alcohol to oil ratio had a positive effect on biodiesel yield. The
6:1 ratio gave rise to the best result, in agreement with previous
researches (Krisnangkura and Simamaharnoop, 1992).
The influence of reaction temperature (X11) on biodiesel yield
was very significant in the range studied (from 35 to 65 C). There
was no decrease in activity at 65 C due to thermophilic characteristic of T. lanuginosus.
Previous study showed that biodiesel conversion depends on
the rate of substrate flow (Nie et al., 2006). A similar result was obtained in our study. Flow rate of substrate and reaction time had
positive effects on biodiesel yield. This shows that the reaction
was less diffusion-controlled.
It is well known that water content is an important factor
affecting the activity of an enzyme in a non-aqueous medium.