08.08.2015   BIOENERGY. RESEARCH:. ADVANCES AND. APPLICATIONS

LIPASE-CATALYZED. TRANSESTERIFICATION DONE IN TWO. APPROACHES

1. Extracellular/free lipase lipases (i. e. recovered and purified from the cultivation broth): For industrial level production of extracellular lipases, bacteria, yeast and fungi are preferred. Lipases from different sources are able to catalyze the same reaction (Table 8.1). Bacterial and fungal lipases are mostly used in biodiesel production and recently, Streptomyces sp. was proved as an effective lipase producing microbe and the enzyme produced was appropriate for biodiesel production (Cho et al., 2012). Use of free or extracellular enzymes was limited due to their price. Cost of the enzyme was increased due to their specific separation and purification techniques. Extracellular lipases are soluble enzymes and they are dispersed in the solution and can move freely during the catalytic reaction, thus difficult to handle and reuse (Iso et al.,

2001) . One auspicious approach to overcome this

Lipase Producing Microorganisms

References

Pseudomonas fluorescens

Iso et al. (2001)

Pseudomonas cepacia

Noureddini et al. (2005)

Candida antarctica

Nelson et al. (1996)

Rhizopus delemar

Nelson et al. (1996)

Rhizopus oryzae

Ghamgui et al. (2004)

Mucor miehei

Nelson et al. (1996)

Geotrichum candidum

Nelson et al. (1996)

Candida rugosa

Shimada et al. (2002);

Ma et al. (2002);

Chowdary and Prapulla (2002)

Rhizomucor miehei

Soumanou and Bornscheuer (2003a, b)

Thermomyces lanuginosa

Iso et al. (2001);

Xu et al. (2003);

Soumanou and Bornscheuer (2003a, b); Du et al. (2003)

Aspergillus niger

Haas et al. (2002)

Pseudomonas cepacia

Noureddini et al. (2005)

Chromobacterium viscosum

Yahya et al. (1998)

Photobacterium lipolyticum

Yahya et al. (1998)

Streptomyces sp.

Yahya et al. (1998); Cho et al. (2012)

TABLE 8.1 Different Microbial Sources for Lipases Used in Biodiesel Production

difficulty is to immobilize the enzyme in a way that can be separated and reused later by using simple separation methods like centrifugation and filtration (Iso et al., 2001; Cao, 2005).

2. Intracellular/immobilized lipases; i. e. lipases remain either inside or attached to the cell wall.

In this case, enzyme is immobilized (naturally) directly or together with the whole cell (intracellular). This strategy eliminates downstream operations and promises the recycling of enzymes. Alternatively lipases can be immobilized synthetically by different mechanisms. Immobilization restricts movement of the enzyme and constrains its location to an inert support or a carrier (Cao, 2005). Various methods like adsorption, covalent bonding, entrapment, and cross-linking are available for enzyme immobilization. The choice of method and support material is a protuberant factor for obtaining an efficient lipase (Table 8.2) (Sevil et al., 2012).

ADVANTAGES OF IMMOBILIZED LIPASE

1. Enzyme becomes more stable.

2. Immobilization of enzyme increases surface area of biocatalyst.

3. Option of regeneration and reuse of the immobilized lipase.

4. Protection from solvent inhibition.

5. Separation of product and enzyme is easier.

6. Avoids contamination of enzyme or whole cell.

7. Rigid external support expected to increase optimal temperature, thereby fasten reaction rate.