514

33 Valorization of Waste Cooking Oil into Biodiesel, Biolubricants, and Other Products

The lipid composition may vary from unsaturated fatty acids to saturated fatty

acids depending on the stage of microbial growth. The lipid content production can

be enhanced using different methods such as metabolic engineering, supplemen-

tation of medium with emulsifiers, surfactants, phosphorus, and magnesium ions.

Furthermore, dispersed waste vegetable oil in water can be used as raw material for

emulsion preparation which can be utilized by microbial consortium of Trichosporon

gracile (fungus) and bacteria to generate versatile microbial lipids [29].

33.4.5

Vitamins and Nutraceuticals

Carotenes play an important role in physiological functions. Studies on carotene

have demonstrated that carotene finds wide applications in strengthening immunity

and osteoporosis and exhibits anticancer activities. Chemically, carotenes are iso-

prene derivatives, mainly tetraterpenoids. Commercially, carotene can be produced

by microbial processing of hydrolyzed mung bean waste flour, grape juice, cheese,

and molasses. Different strains of yeast, bacteria, and fungi can be used for carotene

production. Vegetable oils such as corn oil, sunflower oil, coconut oil, and olive oil

can also be used as feedstock material for microbial carotene synthesis. However,

the high manufacturing costs involved in carotene production using vegetable oils

make this process less feasible for commercial applications. The abundance of WCO

and the feasibility of using WCO for carotene production make it a prospective feed-

stock material. The WCO comprising soyabean oil, cottonseed oil, and corn oil can

be used as a raw substrate material for metabolic action of Blakeslea trispora (mold)

for getting carotene as a by-product [30].

Different vitamins play an important role in the physiological development of

human body. Currently, research is being conducted on synthesizing these vitamins

at pilot scale in order to fulfill the demands for supplementation. Vitamin B12, one

of the vitamins of B complex group, can be synthesized with the help of certain

microorganisms. Synthesis of Vitamin B12 by fermentation is costly, produced in

small amounts, and difficult to separate. Synthesis of food grade vitamin B12 in the

fermentation of microbial strains like Pseudomonas and Propionibacterium is accom-

panied by the production of chemicals like acetic acid and propionic acid which

accumulate and inhibit the cell growth thus adversely affecting the production of

vitamin B12. To overcome the cost involved in vitamin B12 synthesis, cheap feed-

stocks like sucrose, whey, molasses, and waste sunflower cooking oil can be used in

the fermentation of Propionibacterium freudenreichii [31].

33.4.6

Biopolymer Synthesis

Plastics as synthetic polymers mainly comprise of polyethylene units. The com-

monly used plastics for packaging and storage comprise of low-density polyethylene

(LDPE) and high-density polyethylene (HDPE) . The mechanical strength of plastics

can be modulated by altering the content of polyethylene. Polyethylene is mainly

obtained from petroleum which is a nonrenewable source. Because, petroleum is

not able to degrade and the sources are limited, there arises a need for renewable