Biosurfactants for a Sustainable Future. Группа авторов
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2 3.2 Significance of the Production of Biosurfactants from Industrial Products
3 3.3 Factors Affect Biosurfactant Production in Bioreactor
4 3.4 Microorganisms 3.4.1 Bacteria 3.4.2 Fungi and Yeast
5 3.5 Bacterial Growth Conditions 3.5.1 Continuous Cultures 3.5.2 Batch Processes 3.5.3 Fed-Batch Process
6 3.6 Substrate for Biosurfactant Production 3.6.1 Production of Biosurfactant with Food and Vegetable Oil Waste 3.6.2 Development of Biosurfactants Using Waste Frying Oil 3.6.3 Fruit and Vegetable Industry Byproducts for Biosurfactant Processing 3.6.4 Starch-Rich Byproduct from the Industry for Biosurfactant Production 3.6.5 Biosurfactant Synthesis from Lignocellulosic Industrial Byproducts
3.1 Introduction
Surfactants are amphiphilic molecules with two contrary components, one component being hydrophobic and other hydrophilic in nature [1, 2]. Hydrophobic and hydrophilic components depend on the polar charge, which may be anionic, cationic, neutral, or amphoteric. Biosurfactants are emerging as a promising alternative for synthetic surfactants in the industrial sector, as companies develop environmentally safe biosurfactants using various renewable and organic materials. Usually, the surfactants derived from organic substances comprise both hydrophilic and hydrophobic components. Natural surfactants are a group of secondary metabolites that are widely present in many plants, microorganisms and several sea animals [3]. Surfactants are surface‐active chemicals used in detergents and soaps for reducing surface tension. Biosurfactants can be produced from various low‐cost industrial waste materials (Figure 3.1).
Figure 3.1 Schematic representation of the adhesion of bio surfactant molecules to the containment in which bacterial cell is associated (Guerra‐Santos et al., 1984).
They have many benefits over chemical‐derived surfactants, including minimal toxicity, biologically available, biologically degradable, high foaming, and environmentally safe [4, 5]. Therefore, they are safer substitutes for synthetic surfactants, notably in food, medicine, cosmetics, and edible oils [6, 7]. Biosurfactants have an extensive range of applications in different domains such as cosmetics, pharmaceuticals, milk, energy, irrigation, forestry, textiles, painting, and several other sectors. These molecules are commonly known as multifunctional compounds, like stabilizers, wetting agents, antimicrobials, moisturizers, emulsifiers, and antiadhesives [8–11].
3.2 Significance of the Production of Biosurfactants from Industrial Products
The major barrier in the production of biosurfactants is the cost of the production process. It was documented that the main obstacle to large‐scale application of biosurfactants is related to their higher production cost (10–30%) than chemical surfactants. In particular, carbon and energy sources used during the fermentation process cost 50% of the total costs of production of biosurfactants [12–14]. However, the use of alternative nutrient sources that are readily available and cheap may drastically reduce this cost [15]. The usage of industrial waste or byproducts as a source of energy for biosurfactant production may be an effective way to reduce production cost and sustainability of the production process for industries. It was reported earlier [16] that agro‐industrial waste, with a higher protein, fat, and carbohydrate component, is desirable as a production medium component for biosurfactant production.
Similarly, industrial byproducts, i.e. glycerol, petroleum sludge, sugar cane bagasse, and fish waste, could be used as a carbon source for the fermentation process and microbial growth [17]. Several microorganisms, like Bacillus, Corynebacterium, Pseudomonas, and Rhodococcus are capable of producing biosurfactants from various industrial byproducts. Aguiar et al. [18] reported the use of Corynebacterium aquaticum as emulsifying biosurfactant producers by using agro‐waste. Waste discharged from oil‐based industries is severely harmful to the environment and is assumed to be primarily responsible for worldwide pollution. Many of them are neurotoxic, carcinogenic, and poisonous and, therefore, can impact human and animal health [19–21]. Similarly, the solvents used for the removal of paint adversely affect the environment. Searching for new techniques that effectively reduce pollutants is therefore extremely important in order to reduce the adverse impact of industrial wastes.
3.3 Factors Affect Biosurfactant Production in Bioreactor
Various factors influence the biosurfactant production efficiency of microbes. These factors are divided into various categories, but primarily belong to three major groups:
1 The first group of factors includes medium components, i.e. carbon, nitrogen source.
2 The second group includes physicochemical parameters of the microbial community and growth conditions in the bioreactor, i.e. upstream processing [22, 23].
3 The third group includes the product isolation parameters, i.e. downstream processing.
The components of all of these groups have a direct impact on production cost and product quality.
3.4 Microorganisms
Different groups of microorganisms, i.e. bacteria, fungi, and yeasts, are known as potential sources for the production of biosurfactants. Their production potential relies on various environmental and physiological conditions. Each microbe does have optimal conditions for its growth. However, the optimum growth conditions for cells are not always very suitable for the production of the desired product [14, 24]. The quantity of biosurfactants produced depends primarily on the type of microorganism and nutrient type. Most of the microorganisms that have a biosurfactant production capability have been screened from various industrial waste sites, i.e. contaminated soils, effluents, and wastewater discharge points [25]. Therefore, these organisms can grow on industrial byproducts and could be utilized for biosurfactant production under controlled conditions by using industrial waste as