Evaluation of Lipases from Wild Microbial Strains as Biocatalysts in Biodiesel Production

Carlos Luna,Antonio Romero,Juan Calero,Enrique Sancho,Alejandro Posadillo,Diego Luna,Felipa Bautista,Rafael Estevez

doi:10.3390/separations5040053

Abstract

In this study, the evaluation of the catalytic behavior of several wild bacterial strains in the 1,3-selective ethanolysis of triglycerides with ethanol to produce a new type of biodiesel (Ecodiesel) that integrates glycerol as monoacylglycerols was carried out. The Ecodiesel production not only avoids the elimination of glycerol, which is largely generated as a by-product in the biodiesel industry, but also results in an increase in the biofuel yield. The wild microbial strain samples were obtained from several lipophilic organisms. In addition to evaluate the enzymatic extracts, the minimum grade of purification of the strains, necessary to obtain similar results to those attained with commercial lipases was studied. This purification treatment included a dialysis followed by a lyophilization process. Such extracts were directly used as biocatalysts in the transesterification reaction of sunflower oil with ethanol, attaining much better results (yield close to 100%) than those obtained with strains which were not submitted to the purification process (yields lower than 10%). Furthermore, the results here obtained are similar to those obtained with commercial lipases but were achieved under mild conditions and lower reaction time (2 h). In addition, the stability of the enzymatic extracts was corroborated by subsequent reactions, showing no loss of activity. Thus, this study brings to light that enzymatic extracts obtained by a very simple purification process can be economically competitive with the conventional biodiesel production methods.

Highlights

IntroductionThe evaluation of alternative energies which can substitute the non-renewable ones (natural gas, coal, and fossil fuels) for electricity generation is a growing trend for reasons associated with environmental preservation [1,2]
The evaluation of alternative energies which can substitute the non-renewable ones for electricity generation is a growing trend for reasons associated with environmental preservation [1,2]
The lipolytic bacteria were analyzed using a colorimetric assay to detect transesterification activity. This method consists in the transesterification of para-nitrophenyl palmitate (p-NPP) with ethanol in the absence of water to release the yellow-colored compound para-nitrophenol (p-NP), which can be subsequently detected by using a spectrophotometer

Summary

Introduction

The evaluation of alternative energies which can substitute the non-renewable ones (natural gas, coal, and fossil fuels) for electricity generation is a growing trend for reasons associated with environmental preservation [1,2]. Electric motors as well as vehicles capable of using fuel cells are not able to compete with explosion or combustion engines, especially in the aviation field [3]. The search of renewable materials capable of replacing fossil fuels and that allow working with the current engines without any modifications seems to be essential [4]. The only renewable materials considered for the substitution of diesel fuel are vegetable oils or animal fats used as biofuel, and the main existing technology to obtain biodiesel is based on the transesterification of triglycerides with methanol to obtain fatty acids methyl esters (FAME). Different alternative processes have been proposed, such as dilution of the vegetable oils, emulsification, Separations 2018, 5, 53; doi:10.3390/separations5040053 www.mdpi.com/journal/separations

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