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Received Oct 13, 2017; Revised Jan 27, 2018; Accepted Feb 20, 2018
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1. Introduction
Antioxidants function to exert protective effect on human health from oxidative damage caused by reactive oxygen species (ROS) [1, 2]. The ROS such as hydroxyl, superoxide, and peroxyl radicals attack macromolecules including membrane lipids, proteins, and DNA [3] which subsequently lead to serious health complications such as cancer, diabetes mellitus, and neurodegenerative and chronic inflammatory diseases [4–7]. ROS has also been identified to be responsible for deterioration of food products through lipid oxidation [8]. Generally, lipid oxidation occurs during processing, distribution, and storage of food products, thus negatively affecting the food quality, shelf life, and safety. Besides promoting oxidative rancidity, lipid oxidation can lead to loss of fat-soluble vitamins and essential fatty acids as well as generation of undesirable secondary lipid peroxidation products with toxic and carcinogenic effects [9]. In order to retard oxidation and peroxidation processes, several synthetic antioxidants such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), and propyl gallate (PG) have been used by food and pharmaceutical industries for the last century [10]. However, the use of these synthetic antioxidants have been associated with potential health hazards such as liver damage and carcinogenesis [11]. Thus, the concerns over the toxicity of synthetic antioxidants have provided an impetus to search for new and safe antioxidants as alternatives to protect cell in human body against oxidative damage as well as to stabilize fats against oxidative rancidity in food products.
Recently, there is a considerable interest in the food industry as well as pharmaceutical industry for the development of antioxidants derived from natural sources, including plants, animals, and microorganisms [12, 13]. Natural products are rich sources of structurally diverse chemical entities with valuable nutraceutical, pharmaceutical, and cosmeceutical applications [14, 15]. Among them, microbes represent one of the richest sources of bioactive natural products [16]. Microbes have been recognized for their potential in the bioprocess technologies, demonstrating significant advantages over plant extraction and chemical synthesis methods. The advantages of rapid growth rates and ease of cultivation demonstrated by microbial biofactories are...