**1. Introduction**

Globalization and the growth of the population have promoted the expansion of the production of, and investments in, complex food supply dynamics. However, food safety issues arise such as the origin and properties of products and components added to food. Most of these substances, including thickeners, stabilizers and emulsifiers, are important additives for the quality of food [1] because they help maintain or even improve their appearance, freshness, flavor, texture and safety [2].

**Citation:** Durval, I.J.B.; Ribeiro, B.G.; Aguiar, J.S.; Rufino, R.D.; Converti, A.; Sarubbo, L.A. Application of a Biosurfactant Produced by *Bacillus cereus* UCP 1615 from Waste Frying Oil as an Emulsifier in a Cookie Formulation. *Fermentation* **2021**, *7*, 189. https://doi.org/10.3390/ fermentation7030189

Academic Editors: Giuseppa Di Bella and Alessia Tropea

Received: 15 August 2021 Accepted: 10 September 2021 Published: 12 September 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

The search for "green" ingredients has intensified in the food industry thanks to the progress of studies and the increase in competition in the sector as well as the growing interest of consumers for natural ingredients over synthetic additives [3]. This interest is mainly associated with the growing demand for natural, organic and vegan food [4].

Biosurfactants are promising products obtained from biological sources whose attractiveness is due to their biodegradability, specific bioactivity, sustainable production and low toxicity [5,6]. These features give biosurfactants considerable potential for practical applications particularly in the food, cosmetic, healthcare, biomedical and pharmaceutical sectors [5].

The literature describes improvements in the texture, volume and conservation of baked goods due to the addition of biosurfactants. Researchers reported improvements in the viscosity of food products when using microbial emulsifiers, the efficient emulsification of fat from meat products, enhanced solubilization of aromas and a greater stability of salad dressings [1]. Biosurfactants are also effective in solubilizing vegetable oils, stabilizing fats during cooking processes and improving the organoleptic properties of bread. Biomolecules can be used in ice cream formulations, muffins (as an ingredient to replace baking powder and eggs), cookies and salad dressings. The use of microbial emulsifiers was also shown to reduce the use of currently marketed emulsifiers in farinaceous food and to improve their rheology [1,2].

Among the different types of biosurfactants explored, lipopeptides and glycolipids stand out due to their desirable properties for application in the food industry such as antibacterial activity against a variety of species, antioxidant activity and low cytotoxicity. The lipopeptides produced by bacteria of the genus *Bacillus* are examples of microbial biosurfactants obtained by fermentation [7,8] whose main characteristics are an emulsification capacity and a reduction of surface tension along with antioxidant, antiadhesive, antibiofilm, antibacterial, antifungal, antitumor and antiviral properties [6,9].

However, the industrial production of biosurfactants faces great challenges due to the high costs of microbial cultivation and their recovery [10]. One of the solutions to make the industrial production of these biomolecules economically feasible consists of the use of agro-industrial co-products as substrates for the fermentation process, given that the substrate accounts for up to 50% of the final manufacturing cost [7]. The food industry generates waste products that often contain high concentrations of carbohydrates, lipids and proteins, which makes these co-products attractive candidates for fermentation processes [11]. Among such substances, waste cooking oil—which is produced in the kitchens of homes, restaurants and industries—is considered to be hazardous to the environment and human health; therefore, it should be collected to reduce the environmental impact of its improper disposal [12].

A 2019 report on the prospects for the commodities market by the Organization for Economic Cooperation and Development (OECD) and the Food and Agriculture Organization (FAO) of the United Nations states that approximately 210 million tons of vegetable oils are produced and consumed by humans every year. Therefore, the estimated annual global production of waste cooking oil is around 42 million tons [13]. The use of agroindustrial waste products or renewable raw materials in fermentation processes to produce biosurfactants is in line with green chemistry and is an important tool for sustainable innovation, which meets the demands of the current market [14].

Therefore, the aims of the present study were (a) to investigate the use of a biosurfactant produced by *Bacillus cereus* UCP 1615 as an additive in a cookie formulation, (b) to analyze the nutritional benefits of its addition, (c) to check its non-toxicity, (d) to determine its antioxidant potential and (e) to evaluate its effects on the physicochemical properties as well as the texture of the product.
