Biofuels in Perspective

138 Biofuels
ME content (wt.%)
Reaction time (h)
Figure 8.7 Time course of methyl ester content in repeated methanolysis reaction using BSP-immobilized
cells with and without glutaraldehyde treatment (0.1 % solution × 1hat25 ◦ C). The procedure for
immobilization within the BSPs was the same as described in Figure 8.6. Methanolysis was carried out for
6 batch cycles in the presence of 15 % water in the reaction mixture. Symbols: closed circle: treated cells;
open circle: untreated cells. (From Ref. 48, with permission of Elsevier.)
To stabilize the R. oryzae cells, cross-linking treatment with 0.1 % glutaraldehyde
solution was examined. 48 As shown in Figure 8.7, the lipase activity of the cells thus
obtained was maintained without significant decrease during six batch cycles, with the ME
content in each cycle reaching 70–83 % within 72 h. Without the glutaraldehyde treatment,
the activity decreased gradually with each cycle to give an ME content of only 50 % in
the six batch. These findings indicate that the use of whole-cell biocatalyst immobilized
within BSPs (47, 48) offers a promising means of biodiesel fuel production for industrial
application because of the simplicity of the lipase production process as well as the stability
of lipase activity over a long period.
8.4.2 Methanolysis in a Packed-bed Reactor using Cells Immobilized within BSPs
To achieve a higher ME content in the reaction mixture using cells immobilized within
BSPs, Hama et al. 49 demonstrated effective methanolysis using a packed-bed reactor system
shown in Figure 8.8. To increase the interfacial area between the reaction mixture and
the cells immobilized within BSPs, the reaction mixture was emulsified by ultrasonication
prior to reaction in each cycle. Figure 8.9 shows the time course of ME content during ten
repeated-batch cycles of methanolysis in the packed-bed reactor. When stepwise addition
of methanol (four molar equivalents to oils) was conducted, a high ME content of over 90
% was achieved in the first cycle of repeated-batch methanolysis at a flow rate of 25 l/h
and a high value of around 80 % was maintained even after ten batch reaction cycles.
However, although a comparatively high ME content was obtained in the first cycle,
the ME content decreased significantly during repeated methanolysis when using a screwcap
bottle under vigorous shaking. This is probably explained by cell exfoliation, as the