Biotechnological production of biodiesel fuel using biocatalysed transesterification: A review

Biotechnological production of biodiesel has attracted considerable attention during the past decade compared to chemical-catalysed production since biocatalysis-mediated transesterification has many advantages. Currently, there are extensive reports on enzyme-catalysed transesterification for biodiesel production; the related research can be classified into immobilised-extracellular and immobilised-intracellular biocatalysis and this review focusses on these forms of biocatalyst for biodiesel production. The optimisation of the most important operating conditions affecting lipase-catalysed transesterification and the yield of alkyl esters, such as the type and form of lipase, the type of alcohol, the presence of organic solvents, the content of water in the oil, temperature and the presence of glycerol, are discussed. However, there is still a need to optimise lipase-catalysed transesterification and reduce the cost of lipase production before it is applied commercially. Optimisation research of lipase-catalysed transesterification could include development of new reactor systems with immobilised biocatalysts, the use of lipases tolerant to organic solvents, intracellular lipases (whole microbial cells) and genetically modified microorganisms (intelligent yeasts). Biodiesel fuel is expensive in comparison with petroleum- based fuel and 60-70% of the cost is associated with feedstock oil and enzyme. Therefore ways of reducing the cost of biodiesel with respect to enzyme and substrate oils reported in literature are also presented.