## 1 Introduction  
Biodiesel may be produced by the esterification of free fatty acids or the transesterification of oils and fats with short-chain alcohols [1]. Remarkable, biodiesel has been reported as one of the options to replace or complement traditional fuels, using natural raw materials or renewable biological elements for its production [2; 3; 4]. Indeed, it has several advantages for being a renewable, clean, biodegradable,non-toxic and low polluting energy source, compared to petroleum diesel [5]. In this regard, seeking to increase the commercial competitiveness of biodiesel in the market, it is expected that alternative oilseeds will expand its application as a raw material in the production of biodiesel [6; 7]. For instance, babassu (_Orbignya_ sp.) is an oil palm that may be an alternative raw material for the production of biodiesel, as it is a non-edible oil with low cost [8; 9; 10]. The quality of the babassu oil depends on the almonds; in fact, broken or scratched almonds, when exposed to light and moist air, become rancid in proportion to the time of exposure [8], resulting in an oil with high content of free fatty acids. The deteriorating state of the oil is indicated by the proportions of free fatty acids present and can significantly limit its use. Thus, this oil cannot be used as a raw material in the production of biodiesel using alkaline catalysts because it has high acidity. Thus, the production of biodiesel may be carried out through the hydroesterification process, which allows the use of raw material with high concentrations of free fatty acids. The process takes place in two stages, the first of which is the hydrolysis reaction of the glycerides that produce free fatty acids and glycerol. The second stage is the esterification reaction of free fatty acids with a short-chain alcohol for the production of esters and water [9]. In this regard, the literature reports the use of the hydroesterification process for the production of biodiesel, with the hydrolysis stage catalyzed by a lipase and the esterification catalyzed by an acid [11], using commercial lipases in both reactions [12] or even with the hydrolysis stage in subcritical water and use of a lipase in the esterification stage [13]. More and more, the interest in biodiesel production using immobilized lipases has been increasing [14; 15; 16; 17], due to the advantages that the immobilized enzymes offer in relation to the conventional processes that use chemical catalysts [18; 19; 20]. For example, milder reaction conditions, reduced energy consumption, compatibility with the quality of raw materials and recovery of the biocatalyst [21]. In this scenario, Novozym(r) 435 (lipase B from _Candida antarctica_ immobilized on a macroporous resins) the most commonly used lipase in the biodiesel production (see Table 1) [22; 23; 24]. In general, lipases are used in a wide variety of biotransformation through several types of reactions, such as hydrolysis, esterification and transesterification [25]; therefore, they are used for _laboratorial_ and _industrial applications_[26; 27; 28; 29; 30; 31; 32; 33], such as formulation of drugs, modification of racemic alcohols, acids and esters [34]. Besides, lipases can replace synthetic processes in the industry, such as in the cleaning, hygiene, leather, pharmaceutical and food industries (aroma and flavor) [35], once enzyme exhibits a very high degree of substrate specificity and selectivity [36; 37; 38]. To authors' knowledge, up to date, this is the first work reported in the literature that investigates both the production of biodiesel Novozym(r) 435 as a biocatalyst and the free fatty acids obtained from the residual oil from babassu. The chemoenzymatic route used in this communication, chemical hydrolysis followed enzymatic esterification, proved to be an efficient process for the production of biodiesel. Comparatively, transesterification is a slow process that consumes more energy, generating more costs [39].