Page 199 - Biofuels Refining and Performance

182 Chapter Six

water in the starting materials. Oda et al. [45] have reported methanol-
ysis of the same oil using whole-cell biocatalyst, where R. oryzae cells
were immobilized within porous biomass support particles (BSP). Köse
et al. [46] have reported the lipase-catalyzed synthesis of alkyl esters
of fatty acids from refined cottonseed oil using primary and secondary
alcohols in the presence of an immobilized enzyme from C. antarctica,
commercially called Novozym-435 in a solvent-free medium. Under the
same conditions, with short-chain primary and secondary alcohols, cot-
tonseed oil was converted into its corresponding esters.
Alcoholysis of soybean oil with methanol and ethanol using several
lipases has been investigated. The immobilized lipase from Pseudomonas
cepacia was the most efficient for synthesis of alkyl esters, where 67 and
65 mol% of methyl and ethyl esters, respectively, were obtained by
Noureddini et al. [47]. Shimada et al. [48] have reported transesterifi-
cation of waste oil with stepwise addition of methanol using immo-
bilized C. antarctica lipase, where they have successfully converted
more than 90% of the oil to fatty acid ME. They have also implemented
the same technique for ethanolysis of tuna oil.
Dossat et al. [49] have found that hexane was not a good solvent as
the glycerol formed after the reaction was insoluble in n-hexane and
adsorbed onto the enzyme, leading to a drastic decrease in enzymatic
activity. Enzymatic transesterification of cottonseed oil has been stud-
ied using immobilized C. antarctica lipase as catalyst in t-butanol sol-
vent by Royon et al. [50].
Sometimes, gums present in the oils used inhibit alcoholysis reactions
due to interference in the interaction of the lipase molecule with sub-
strates by the phospholipids present in the oil gum. Crude soybean oil
cannot be transesterified by immobilized C. antarctica lipase. So,
Watanabe et al. [51] have used degummed oil as a substrate for a trans-
esterification reaction, in order to minimize this problem, and have effec-
tively achieved conversion of 93.8% oil to biodiesel.
Methanol is insoluble in the oil, so it inhibits the lipases, thereby
decreasing its catalytic activity toward the transesterification reaction.
Du et al. [52] transesterified soybean oil using methyl acetate in the
presence of Novozym-435 (see Fig. 6.15). Further, glycerol was also insol-
uble in the oil and adsorbed easily onto the surface of the immobilized
lipase, leading to a negative effect on lipase activity. They have suggested
that methyl acetate was a novel acceptor for biodiesel production and
no glycerol was produced in that process, as shown below: