## 1 Introduction  
The environmental concerns associated with the use of fossil fuels have encouraged the research for biofuel production alternatives [1]. Biodiesel is the most popular alternative energy source to replace fuel owing its sustainability, renewability and reduced emissions [2]. This biofuel is a \(n\)-fuel composed of mono-alkyl esters of long-chain fatty acids that come from vegetable oils or animal fats [3]. Its main characteristics are biodegradability, low sulfur content, no aromatic compounds, a high flash point, characteristic lubrication, miscibility with petroleum diesel and higher cetane number [4]. The main drawback of biodiesel production is the relatively higher production costs in comparison to conventional fossil fuel; however, such costs can be reduced by the use of cheap and available feedstocks such as waste cooking oil, animal fats, palm fatty acid distillate (PFAD) and Jatropha curcas oil [5]. Among these, waste frying oils (WFO) have been widely employed as raw material for biodiesel production in order to provide waste valorization solution [6; 7; 8; 9]. Waste frying oil or cooking oil is inedible oil generated by catering industry and food processing industry. To reduce costs, these industries fry the oils several times under high temperature and in the presence of oxygen and light [10]. This process causes both physical and chemical property changes such as change in color, odor, viscosity and calorie count [11]. It is estimated that the global production of WFO amounts to 5 million tonnes every year [12]. In East Colombia (Cucuta), a large local restaurant consumes in average 80 L of frying oil per month, and 71% of these restaurants reuse the oils three times or more [13]. The cost of WFO is two to three times lower than refined vegetable oils [14]. It is considered a hazardous material with harmful impacts on the environment and has created serious problems for disposal due to its slow degradation [15]. The human consumption of WFO may cause serious health hazards, e.g., potential gastrointestinal disorders and even mutagenesis in the human body [16]. Transesterification is a common technique to provide biodiesel as of glycerides current in oleaginous biomass sources, which react with alcohol to produce alkyl esters and glycerol [17]. Methanol and ethanol are the most used alcohols in the process forming methyl esters or ethyl esters, respectively [18]. During conventional transesterification process, the high amount of free fatty acids (FFA) in WFO are converted to soap and reduce the purity of biodiesel [10]. To date, different types of catalysts have been used to enhance transesterification process and increase biodiesel production yield. [PERSON] et al. [19] studied the acidity removal and subsequent transesterification at different temperatures and mole ratios to enhance the biodiesel production from WFO. They reported nonpolar FAME content of 88.5 wt.% and acid value below 1 mg KOH:g\({}^{-1}\) oil. [PERSON] et al. [20] converted WFO into biodiesel by alkali-catalyzed transesterification and evaluated the effect of operating variables such as reaction temperature, methanol (MeOH)/oil ratio and type of catalyst. The optimum conditions reported by such contribution were MeOH/oil ratio 0.4 \(\psi\)/c, 1.0% \(\
u\)/c KOH, a temperature of 50 \({}^{\circ}\)C and reaction time between 20 and 40 min. [PERSON] et al. [21] used different type of WCO (sunflower, maize, olive and a blend of soybean, palm and sunflower) to study the influence of oil source on biodiesel quality and suggested transesterification method for WFO with densities (at 15 \({}^{\circ}\)C) of up to 930 kg/m\({}^{3}\). The use of enzymes to catalyze transesterification reaction is being widely studied because they can promote esterification of FFA and transesterification of triacylglycerols simultaneously [22]. [PERSON] et al. [23] used waste vegetable oils to produce biodiesel via enzymatic transesterification using lipase from _Pseudomonas cepacia_.