Abstract The interest for oleaginous yeasts has grown significantly in the last three decades, mainly due to their potential use as a renewable source of microbial oil or single cell oils (SCOs). However, the methodologies for cell disruption to obtain the microbial oil are considered critical and determinant for a large-scale production. Therefore, this work aimed to evaluate different methods for cell wall disruption for the lipid extraction of Yarrowia lipolytica QU21 and Meyerozyma guilliermondii BI281A. The two strains were separately cultivated in 5 L batch fermenters for 120 hours, at 26 ºC and 400 rpm. Three different lipid extraction processes using Turrax homogenizer, Ultrasonicator and Braun homogenizer combined with bead milling were applied in wet, oven-dried, and freeze-dried biomass of both strains. The treatment with the highest percentage of disrupted cells and highest oil yield was the ultrasonication of oven-dried biomass (37-40% lipid content for both strains). The fact that our results point to one best extraction strategy for two different yeast strains, belonging to different species, is a great news towards the development of a unified technique that could be applied at industrial plants.

Abstract We applied ultrasonic technology for the transesterification of soybean oil catalyzed by a mixture of lipases (combi-lipase: 75 % Novozym 435; 10 % Lipozyme TL-IM; and 15 % Lipozyme RM-IM), verifying the effects of ultrasonic amplitude, pulse conditions, the ethanol:oil molar ratio, enzyme concentration, and the influence of solvent (tert-butanol on the reaction. We also compared this system against ultrasound combined with mechanical stirring, and the efficiency of the combi-lipase, compared with the individual use of each lipase. The optimum conditions for the transesterification reaction were determined as enzyme concentration of 15 % (in relation to oil mass); ethanol:oil molar ratio of 3:1; ultrasonic amplitude of 30 %, duty cycle of 50 % and time pulse of 15 sec. The yields of conversion of ethyl esters with and without solvent were similar, indicating that the use of solvents during enzymatic transesterification reactions is not necessary when ultrasonic technology is applied to the system. The combination of mechanical stirring and ultrasound did not improve the yields of conversion compared to ultrasonic technology alone. The proposed combi-lipase produced higher yields of ethyl esters (75 %) than the individual lipases (55 %) in 5 h under ultrasonic-assisted batch reactions.

In this study, Klebsiella pneumoniae BLh-1 was grown under exponential fed-batch mode in cultures using raw glycerol from biodiesel synthesis under anaerobiosis to produce value-added products. Specific growth rates of 0.035, 0.07, and 0.105 h-1 were tested and 1,3-propanediol (1,3-PDO) and ethanol were produced in all cultures, whereas the formation of 2,3-butanediol was not observed. The highest concentrations of 1,3-PDO (38.5 g L-1) and ethanol (13.2 g L-1) were achieved under the specific growth rate of 0.105 h-1. Acetic and lactic acids were also produced at high concentrations (17.3 and 7.8 g L-1, respectively) under these conditions. The yields of 1,3-PDO and ethanol increased over time, reaching final values of 0.56 and 0.19 g g-1, respectively. Overall productivities were 1.43 g L-1 h-1 for 1,3-PDO and 0.49 g L-1 h-1 for ethanol. Compared to batch results, fed-batch operation favored K. pneumoniae metabolism towards the production of 1,3-PDO and ethanol, being an interesting process to add value to the ever-growing availability of raw glycerol from biodiesel industry.

We carried out the physico-chemical characterization of Immobead 150, a hydrophobic support for the immobilization of lipases. Thermomyces lanuginosus lipase (TLL) was immobilized on Immobead 150 by multipoint covalent attachment (ImmTLL) and the morphological, textural, structural, thermal, and physico-chemical properties of the support, before and after enzyme immobilization, were investigated. Immobead 150 presents approximately 1,000 µmol of epoxy groups per gram of support, a high hydrophobicity, and good thermal stability. The spherical particles of Immobead 150 present average diameters of 155 µm, specific surface areas of 137 m2 g-1 and pore volumes of 0.37 cm3 g-1, showing pores in the region of the micro and meso sizes. The immobilization process of TLL (150 mg g-1) caused a decrease of the specific area and pore volumes, to 63 m2 g-1 and 0.25 cm3 g-1, respectively, as a result of coating of the support surface by the enzyme molecule. However, the immobilization process did not affect the morphology of the support. The obtained biocatalyst was effective for the syntheses of fatty acid ethyl esters (biodiesel), and of aroma esters, showing yields of 68 and 70%, respectively, similar to commercial preparations used as controls.