Innovative methodologies for the production of microbial oils and biodiesel

Abstract

Nowadays research has focused on new energy sources to limit the use of traditional fossil fuels and promote the development of biorefineries. In this context, an important goal is the exploitation of lignocellulosic materials obtained from agro-forestry wastes for the synthesis of II-generation biofuels. Among them, one of the most relevant is biodiesel, obtained using as feedstock the lipids extracted from the oleaginous microorganisms such as yeasts, produced by fermentation in hydrolysates of lignocellulosic biomass. These oils can be transformed in biodiesel performing a transesterification reaction. The production process is still too much expensive and not completely sustainable, due to several energy-intensive steps involved and the use of toxic solvents for the extraction. The aim of this study is to overcome some of the issues bound to the traditional production process of microbial oils and biodiesel, introducing some innovative techniques, such as microwaves and pulsed electric fields. The latter have been already explored in different branches of research, from the food industry to the medicine and in this thesis have been applied on Lipomyces starkeyi and Metschnikowia pulcherrima samples. The main variables investigated during a microwave extraction are the solvent choice, the temperature and the time of extraction, in comparison to the conventional extraction. 1H-NMR analysis were made to characterize the lipid profile of the extracted oils. Furthermore, some direct transesterification tests were conducted and the fatty acids methyl esters obtained are analyzed by gas-chromatography. Concerning to the pulsed electric fields, confocal microscopy has been utilized to investigate the possibility of using this treatment on the yeast’s cell and to understand the effects of some variables such as the concentration of the cell suspension on the efficiency of the application. The results obtained pave the way to the opportunity of using those innovative approaches on an industrial scale.