CHAPTER ONE
INTRODUCTION
Background of studies
Synthetic polymers identified as plastics are one of the human inventions developed into many industries and commodities in day-to-day life (Sudesh and Iwata, 2008). They are designed to be of high performance and stability to make it resistant to chemical and natural conditions. These petroleum-based plastics are very stable in harsh conditions especially against the attack of chemical degradation and microbial decomposition, which renders them durable, highly resistant and a very long life span in the environment. Due to their excellent properties and wide range of application, synthetic plastics have since taken over the commodity market and the technologies related to plastics manufacturing are very well established. Because of the increasing environmental problems associated with discarded plastics, many studies have been directed towards the development of a suitable eco-friendly material that can replace at least some of the commodity plastics (Shraddha et al., 2011). Polymers represent compounds produced by microorganisms under different environmental conditions and are chemically non-related. (Degeest et al, 2001; Sudesh and Iwata 2008). Since the dependence on synthetic plastics and their different products have resulted in accumulation of waste and greenhouse gas emission, recent technologies are now focusing on developing a bio-green substituent for plastic that exerts negligible side effects on the environment (Bhat et al., 2017).
Bio-plastics vary in their basic structure, structure of molecules and physical properties depending on their microbial origin, and most of them are characterized as biodegradable and biocompatible, making it extremely important in terms of biotechnology. Bio plastic is a special type of biomaterial. They are polyesters, produced by a number of microorganisms that develop under certain environmental conditions and under different nutrients. (Akiyama et al., 2003). According to Gatea et al. (2018), Polyhydroxyalkanoate (PHA) is one of these biomaterials, which has received intensive attention because it possesses biodegradable thermoplastic properties. Polyhydroxyalkanoates (PHAs) are bacterial products which are characterized by natural, renewable and biologically active polymers. Plastic materials with similar characteristics to plastics and petrochemicals can be substituted for these materials in many applications (Philip et al., 2007).
Jiang et al. (2016). also explained that Polyhydroxyalkanoates (PHAs) are a group of bacterial polyesters produced by a variety of prokaryotic microorganisms under unbalanced nutrition conditions as carbon and energy storage materials and are currently produced by many companies due to their biodegradability, biocompatibility and thermal process ability. Polyhydroxybutyrate (PHB) is the main member of the PHA family that is accumulated inside numerous bacteria under limiting nutrient conditions with excess carbon. Many researchers have shown that number of microorganisms like Alcaligenes eutrophus, Azotobacter beijierinckia, Pseudomonas Oleovorans, Rhizobium sp. etc., produce PHAs as reserve food material. PHB degrade naturally and completely to CO2 and H2O under natural environment by different microorganisms (Hawas et al., 2016). PHB are non-toxic, biocompatible, biodegradable thermoplastics that can be produced from renewable resources. They have a high degree of polymerization, are highly crystalline and insoluble in water. These features make them highly competitive with polypropylene, the petrochemical-derived plastics (Reddy et al., 2003).
PHBs are natural polyesters that are stored as intracellular inclusions by a great variety of bacteria such as Staphylococcus, Alcaligenes, Bacillus, Pseudomonas, Micrococcus and Rhodococcus and they have characteristics similar to those of standard synthetic plastics Polyhydroxylalkanoates (PHAs) are the most studied thermoplastic bio polymers, discovered for the first time by Lemogine in 1926 and have numerous applications in different fields of life, they are used in clothing, industrial products, fluid containers, wrapping and building materials, packaging films, toys household, shopping and garbage bags(Ali et al., 2017).
1.2 Statement of Problem
Studies have revealed that the main factor preventing the large-scale production and commercialization or sales of PHB is their high cost of production. One of the major factors adding to the cost of PHB is the cost of substrates used for production. Therefore, less expensive substrates and improved cultivation strategies are required for reducing the cost. Thus, utilization of media containing cheaper carbon should be used to reduce the production costs of PHB (Ahn et al., 2000; El-kadi, 2014).
1.3 Justification for the Study
The productions of bio plastics from inexpensive carbon source can help solve the problem of the cost of bio-plastic production as well as reduce plastic waste generation.
1.4 Aim and Objectives
The aim of this study is to isolate PHB producing strains of bacteria from engine oil contaminated soil and study the effect of simple sugars on their production of PHB.
Objectives include:
To isolate and identify bio plastic producing strains of bacteria from engine oil contaminated soil
To screen the bacterial isolates for PHB production
To produce and quantify bio plastics from these isolates
To determine the effect of simple carbon sources on PHB production.
