Showing papers by "Rafael C. Rodrigues published in 2019"

Ultrasound-assisted transesterification of soybean oil using combi-lipase biocatalysts

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.

Improvement of Enzymatic Assisted Extraction Conditions on Anthocyanin Recovery from Different Varieties of V. vinifera and V. labrusca Grape Pomaces

Abstract: The incomplete anthocyanin extraction during the industrial processes turns grape pomace into an inexpensive source of phenolic compounds. The effects of temperature and enzyme preparation percentage (% E/S) on the anthocyanin recovery from grape pomaces of eight grape varieties were evaluated by their physicochemical characteristics and phenolic composition. A factorial 22 design with center point was used to select the preferred conditions for extraction, and the variables of temperature, enzyme preparation, and their interaction were assessed. The grape skin characteristics affected the anthocyanins’ content and their recovery yield, and different improvement conditions were found for each variety of grape. Anthocyanin extraction from Cabernet Sauvignon—the variety which showed the highest percentage of anthocyanin recovery (over 50%)—was improved. The lowest tested temperature (40 °C) and percentage of preparation enzymatic (0.25% E/S) promoted higher anthocyanin extraction, resulting in a natural food colorant with 2.67 g anthocyanins/100 g grape skin dry basis (db). The extraction improvement allowed for a non-toxic natural extract rich in anthocyanins to be obtained; a natural additive which can be considered for potential food industry use in place of synthetic dyes, especially into acidic matrices.

Stability/activity features of the main enzyme components of rohapect 10L

Abstract: Rohapect 10L is an enzyme cocktail commercialized for juice clarification. Here, we characterized the activity and stability of five enzymatic activities present in this cocktail: total pectinase (PE), polygalacturonase (PG), pectin lyase (PL), pectin methyl esterase (PME), and total cellulase (CE) activities. All these enzyme activities have the maximum activity and stability at pH 4, conditions near those found in most fruit juices. However, if the enzymes need to be handled under different conditions (e.g., to immobilize them), their stability becomes extremely low in some cases, just at pH values slightly higher than the optimal one. For example, at pH 10 only CE was reasonably stable at 25°C, while many other enzyme activities were rapidly almost inactivated, even at 4°C. For these cases, different additives were evaluated, and we found that polyethylene glycol was positive or very positive for all enzyme stabilities, allowing keeping reasonable activities after several hours at pH 10 and 25°C. Another additive, that is, dextran, has a small positive effect for PE, PG, and CE, and a very positive effect for PL, albeit significantly destabilizing PME. Thus, the handling and use of this extract requires some care when is performed out of optimal conditions.

Segmentation of Skeletal Muscle in Thigh Dixon MRI Based on Texture Analysis.

Abstract: Segmentation of skeletal muscles in Magnetic Resonance Images (MRI) is essential for the study of muscle physiology and diagnosis of muscular pathologies. However, manual segmentation of large MRI volumes is a time-consuming task. The state-of-the-art on algorithms for muscle segmentation in MRI is still not very extensive and is somewhat database-dependent. In this paper, an automated segmentation method based on AdaBoost classification of local texture features is presented. The texture descriptor consists of the Histogram of Oriented Gradients (HOG), Wavelet-based features, and a set of statistical measures computed from both the original and the Laplacian of Gaussian filtering of the grayscale MRI. The classifier performance suggests that texture analysis may be a helpful tool for designing a generalized and automated MRI muscle segmentation framework. Furthermore, an atlas-based approach to individual muscle segmentation is also described in this paper. The atlas is obtained by overlaying the muscle segmentation ground truth, provided by a radiologist, after image alignment using an appropriate affine transformation. Then, it is used to define the muscle labels upon the AdaBoost binary segmentation. The developed atlas method provides reasonable results when an accurate muscle tissue segmentation was obtained.

STABILIZATION STUDY OF TETRAMERIC Kluyveromyces lactis β-GALACTOSIDASE BY IMMOBILIZATION ON IMMOBEAD: THERMAL, PHYSICO-CHEMICAL, TEXTURAL AND CATALYTIC PROPERTIES

Abstract: We investigated the immobilization of a tetrameric Kluyveromyces lactis β-galactosidase (EC: 3.2.1.23) (KL-Gal) on Immobead 150 using different support modification strategies. Immobead support was modified using an acid solution of H2SO4:HNO3 (3:1) (Immobead-Ac) or 5 % (v/v) glutaraldehyde (Immobead-Glu). Its unmodified form (Immobead) was also tested. Immobilization yields and efficiencies were evaluated by testing protein loads from 10 to 200 mg.g-1 support. The thermal, physico-chemical, textural and catalytic properties of the supports (modified and unmodified) and their derivatives (Immobead-KL-Gal, Immobead-Ac-KL-Gal and Immobead-Glu-KL-Gal) were analyzed. The highest immobilization yields and efficiencies were achieved with a protein load of 100 mg.g-1 support. Surface and pore areas of the Immobead support were greatly decreased after modification. Michaelis constant of the immobilized β-galactosidase increased in the derivatives. Maximum velocity decreased approximately 2.8 times for Immobead-KL-Gal and Immobead-Glu-KL-Gal, and approximately 1.4 times for Immobead-Ac-KL-Gal. In batch processes, the three derivatives could be reused successfully at least 15 times, maintaining high residual enzymatic activity during the lactose hydrolysis (in both cheese whey and milk). The tetrameric K. lactis β-galactosidase immobilized on Immobead supports via the tested treatments was stabilized and is an alternative tool for lactose hydrolysis in the dairy industry.

Preparation of immobilized/stabilized biocatalysts of β-glucosidases from different sources: Importance of the support active groups and the immobilization protocol.

Abstract: β-Glucosidases from two different commercial preparations, Pectinex Ultra SP-L and Celluclast® 1.5L, were immobilized on divinylsulfone (DVS) supports at pH 5.0, 7.0, 9.0, and 10. In addition, the biocatalysts were also immobilized in agarose beads activated by glyoxyl, and epoxide as reagent groups. The best immobilization results were observed using higher pH values on DVS-agarose, and for Celluclast® 1.5L, good results were also obtained using the glyoxil-agarose immobilization. The biocatalyst obtained using Pectinex Ultra SP-L showed the highest thermal stability, at 65°C, and an operational stability of 67% of activity after 10 reuses cycles when immobilized on DVS-agarose immobilized at pH 10 and blocked with ethylenediamine. The β-glucosidase from Celluclast® 1.5L produced best results when immobilized on DVS-agarose immobilized at pH 9 and blocked with glycine, reaching 7.76-fold higher thermal stability compared to its free form and maintaining 76% of its activity after 10 successive cycles. The new biocatalysts obtained by these protocols showed reduction of glucose inhibition of enzymes, demonstrating the influence of immobilization protocols, pH, and blocking agent.

A Quality of Recognition Case Study: Texture-based Segmentation and MRI Quality Assessment

Abstract: Muscle texture may be used as a descriptive feature for the segmentation of skeletal muscle in Magnetic Resonance Images (MRI). However, MRI acquisition is not always ideal and the texture richness might become compromised. Moreover, the research for the development of texture quality metrics, and particularly no-reference metrics, to be applied to the specific context of MRI is still in a very early stage. In this paper, a case study is established from a texture-based segmentation approach for skeletal muscle, which was tested in a thigh Dixon MRI database. Upon the obtained performance measures, the relation between objective image quality and the texture MRI richness is explored, considering a set of state-of-the-art no-reference image quality metrics. A discussion on the effectiveness of existing quality assessment methods in measuring MRI texture quality is carried out, based on Pearson and Spearman correlation outcomes.