Enzymes particularly lipases have been put forward in transesterification reaction mainly to overcome the drawbacks of chemical catalysts. The benefits of using

lipases as “potential biocatalyst” include easy recovery of biodiesel and glycerol, complete conversion of FFA to methyl/ethyl ester without pretreatment, ease of enzyme recovery, low temperature and energy inputs, mild reaction conditions, thermal stability at low temperature, operational stability, can accept wide variety of substrates and alcohols, and reaction in a solvent and solvent-free systems (Casimir et al. 2007). On the other hand, the main hurdle of using enzymes as bio­catalyst is its high cost. This can be overcome to a certain extent through immobilization.

It is crucial to identify a lipase with maximum conversion rate and which is read­ily available in the market. For this, various lipases have been screened for biodiesel production, and the lipase from Pseudomonas cepacia (Burkholderia cepacia) has shown good results (Otero et al. 2005; Shah and Gupta 2007). Several researches have been reported with lipase on transesterification of Jatropha oil and are shown in Table 12.5. A high conversion rate can be seen from the table, but the longer reac­tion time is one of the hurdles in its commercialization.

In order to be more economical when using lipases as biocatalysts, researchers are involved in the development of a robust immobilized enzyme for biodiesel pro­duction. Different combinations of basic immobilization techniques (adsorption, cross-linking, entrapment, encapsulation) are being tried in various ways for this reason. Out of these, entrapment and encapsulation in natural polymers like sodium alginate and k-carrageenan are gaining importance due to environmental friendly and low toxicity features (Jegannathan et al. 2009).