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

33.4

Versatile Products as an Outcome of Valorized

Waste Cooking Oil

33.4.1

Biosurfactants and Liquid Detergents

Biosurfactants are compounds exhibiting surface activity and properties of reduc-

tion in interfacial tension. Biosurfactants possess a hydrophilic and hydrophobic

group imparting them with amphiphilic character and governing their orientation

activity at the solid–liquid, liquid–liquid, or liquid–gas interfaces. They are com-

monly obtained from biological sources. Owing to their surface-active properties,

they have been used in versatile domains of waste treatment protocols comprising

of elimination of heavy metals and removal of oil spills from natural land and

aquatic resources. Their properties of foam generation, emulsion stabilization, and

high wetting will help in their waste treatment functions [18].

Surfactants can be produced by chemical or synthetic means. Owing to the com-

plex procedures involved in the manufacturing of chemical surfactants and their

complex remediation measures, various biological means have been adopted to pro-

duce eco-friendly surfactants. One of such methods is the use of microbial organisms

belonging to Candida, Rhodococcus, Bacillus, and Pseudomonas genera to produce

biosurfactants in varied controlled environmental conditions. These biosurfactants

exhibit higher cleansing action of high specificity with added benefits of biodegrad-

ability and ease of remediation [19].

The WCO- and agriculture-derived wastes have been found to be commonly

explored sources for biosurfactant generation using microbiological methods.

Different microbial strains utilized for biosurfactant production using WCO as the

substrate include Pseudomonas aeruginosa, Pseudozyma aphidis, Candida lipolytica,

and Bacillus. In order to optimize the quality and yield of biosurfactant production,

several optimization strategies utilizing models like Plackett–Burman design and

Taguchi have been adopted [20].

Biosurfactant production trials involving vegetable oils as carbon sources for fer-

mentation have indicated that they prove to be most economical substrates for gen-

erating biosurfactants utilizing the aforementioned microbial species. The desirable

microbial strains effective in catalyzing the conversion of oil to biosurfactant can be

screened using different advanced techniques. The screening of six microbial strains

for the generation of biosurfactant from coconut oil was found to indicate that the

P. aeruginosa D will yield maximum amount of rhamno lipid homologs, mainly the

mono rhamnolipids and di rhamnolipids [21].

There are several means to utilize the WCO. Among those, one of the effective

means of remediation of WCO is its utilization to produce liquid soaps or deter-

gents. Surface-active agents containing suitable functional groups in combination

with amines have been used for the conversion of cooking oil into chemical func-

tionalities with cleansing activity and detergency. Furthermore, the rich fatty acid

contents of WCO have been explored as raw materials for biodetergent generation

using alkaline hydrolysis treatment [22].