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and Table 1.2. for fungal lipases that are used for biodiesel production [46]. Some of the commercially available enzymes for biodiesel production are enlisted in Table 1.3.

1.8 Comparative Analysis of Intracellular and Extracellular Lipases for Biodiesel Production

Transesterification reaction for biodiesel production is done with both extracellular and intracellular lipases. Preference for their use is dependent upon either we want simple upstream processes as in case of intracellular lipase or high enzymatic conversion as in case of extracellular lipase. But either we use intracellular lipase or extracellular lipase there is no need for some downstream processes including separation and recycling. Further, both immobilized lipase (extracellular) and immobilized whole-cell lipase (intracellular) are proved to have highly efficient when compared with free lipase used for transesterification [165]. Some experimental studies for both intracellular and extracellular lipases are given in Table 1.5. Intracellular lipases are the enzymes present inside the cells or linked to the walls of cells producing it known as whole-cell biocatalysts. They are not purified or separated from their cells and used as a whole-cell for transesterification (whole-cell biocatalyst) or immobilized (whole-cell immobilization) [55]. Rhizopus and Aspergillus which are filamentous fungi are most widely used as whole-cell biocatalyst for transesterification process [166]. As the main issue related to biodiesel production at large scale is cost and the use of intracellular lipase for transesterification resolves this problem like the use of intracellular lipase is considered cost-effective because of the elimination of costly processes of lipase isolation and purification before immobilization which are required in case of extracellular lipase [167]. Intracellular lipase producing cells or whole-cell biocatalysts are directly employed for immobilization without separation and purification steps for lipase enzymes [55]. Porous biomass support particles (BSPs) are mostly used for whole-cell immobilization. BSPs was developed by Atkinson et al. [168] and used by many scientists and each scientist provide an efficient way of immobilization on it giving out a high yield of biodiesel. A study to check the lipolytic activities of Bacillus species using intracellular as well as extracellular lipase showed higher intracellular lipase activity than extracellular lipase activity [169]. Reported whole-cell biocatalysts are Aspergillus oryzae, Burkholderia cepacia, filamentous fungus Rhizopus chinensis, R. oryzae, and Enterococcus faecium [170–174]. Aspergillus oryzae used as whole-cell biocatalyst exhibited 98.1% relative stability after the fourth batch and produced more than 97% FAME in 32 hours. Extracellular lipases are the purified form mainly fungal and bacterial cells for their use in transesterification process.

      Table 1.1 Some of the commonly used bacterial lipases for biodiesel production.

Enzyme	Immobilized on	Substrate	Acyl acceptor	Yield	Reference
Burkholderia cepacia Lipase	Hydrophobic silica monolith	Jatropha oil	Methanol	95%	[125]
	Hybrid matrix of alginate and κ-carrageenan	Jatropha curcas L. oil	Ethanol	100%	[126]
	κ-carrageenan	Palm oil	Methanol	100%	[127]
	Modified attapulgite	Jatropha oil	Methanol	94%	[128]
	SiO2-PVA	Babassu oil	Ethanol	100 %	[129, 130]
	SiO2-PVA	Babassu oil	Ethanol	100%	[131]
	Nb2O5	Babassu oil	Ethanol	74.1%	[132]
Pseudomonas cepacia Lipase	Epoxy-acrylic resin	Waste vegetable oil	Ethanol	46–47%	[133]
	Phyllosilicate solgel matrix	restaurant grease	Methanol and Ethanol	98%	[134]
	Fe3O4 nanoparticle biocomposite	Soybean oil	Methanol	>88%	[135]
	Accurel	Madhuca indica	Ethanol	96%	[136]
	Protein-coated microcrystals	Soybean oil	Ethanol	98.93%	[137]
	Celite	Jatropha oil	Ethanol	98%	[89]
Pseudomonas fluorescence	Octyl-silica resin	Babassu oil	Ethanol	97.5%	[85]
	Hydrophobic sol-gel	Soybean oil	Methanol	65%	[138]
	Porous kaolinite particles	Triolein	Methanol and Ethanol	90%	[139]
	Asymmetric membrane	Triolein	Methanol	80%	[140]

Table 1.2

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