33.4 Versatile Products as an Outcome of Valorized Waste Cooking Oil

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natural sources for plastic synthesis. Polyethylene obtained from natural sources is

known as bio-based polyethylene and less contributes to environmental pollution

owing to degradable nature. Relatively, lower greenhouse emissions have been

observed by the use of bio-based plastics [32].

One of the ways for producing plastics with biodegradable properties is mixing

natural biodegradable monomeric units with plastic precursors such as polyethy-

lene. Presence of biorenewable materials in raw substrates can aid to alter the desir-

able extremes of processing conditions for plastic synthesis. Processing temperature

of injection molding is one such condition which can be lowered by the addition

of biorenewable monomeric units thus aiding to lower the energy consumption.

Waste vegetable oil can be used to generate hydroxylated biorenewable biopolymer

using appropriate catalyst systems and processing conditions. Furthermore, WCO

like waste soyabean cooking oil can be processed by the addition of suitable chem-

icals such as maleic anhydride for the synthesis of new polymers with desirable

properties [33].

33.4.7

Polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are polymers produced by certain microorganisms

when subjected to stress conditions like nutrient deficiency. PHAs are aliphatic

esters with high molecular weight and excellent biodegradation profile and exhibit

use as bioplastics. PHAs can be metabolized by microbes using enzymes like lipases

and esterases. Based on the number of monomers units and chain length, PHAs

are classified into short-chain length polyhydroxyalkanoates (SCL-PHAs) and

medium-chain length polyhydroxyalkanoates (MCL-PHAs). Palm oil and other

carbon sources have been used by microbial species to produce PHAs [34].

The feedstock containing combination of xylose, glucose, and fatty acid can be

utilized by Escherichia coli for the production of PHAs. Industrial synthesis of PHAs

involves the use of costly raw materials. The WCOs like palm oil, corn oil, soybean

oil, sunflower oil, and coconut oil with their high saturated and unsaturated fatty

acid content serve as excellent carbon sources for the synthesis of PHAs. Microbial

strains of Pseudomonas, Bacillus, Klebsiella pneumoniae, and Cupriavidus necator

are commonly used for PHA synthesis from WCO. The PHAs are produced as intra-

cellular granules and exhibit versatile uses in diverse fields like food industry, tissue

engineering, etc. As raw material substrate for PHA synthesis, the WCO is found to

be a prospective starting material as compared to sugars in terms of commercial via-

bility. The yield of PHAs is affected by the source of cooking oil and can be enhanced

by genetic manipulations. High yield of PHAs can be obtained using WCOs with

saturated fatty acids like palmitic acid [35].

33.4.8

Feedstock for Microbial Processes

Some of the desirable properties for fermentable raw materials to be used as input for

the generation of industrially viable products are the percent content of carbon and

nitrogen, ease of processing and disinfection, economical viability, easy availability,