Gabriela Rodríguez-Serrano

Robusta coffee beans post-harvest microflora: Lactobacillus plantarum sp. as potential antagonist of Aspergillus carbonarius.

Coffee contamination by ochratoxigenic fungi affects both coffee quality as well as coffee price with harmful consequences on the economy of the coffee exporting countries for whom which is their main source of income. Fungal strains were isolated from coffee beans and identified as black Aspergilli. Ochratoxigenic moulds like Aspergillus carbonarius were screened and selected for detailed studies. Also lactic acid bacteria (LAB) were isolated from silage coffee pulp and their antifungal activity was tested on dual-culture agar plate. Ten of the isolated LAB demonstrated antifungal effect against A. carbonarius. API 50 CH and APIZYM were used to perform phenotypic identification. 16S rDNA sequencing was made to confirm the results.

Biotransformation and improved enzymatic extraction of chlorogenic acid from coffee pulp by filamentous fungi

The highest enzymatic extraction of covalent linked chlorogenic (36.1%) and caffeic (CA) (33%) acids from coffee pulp (CP) was achieved by solid‐state fermentation with a mixture of three enzymatic extracts produced by Aspergillus tamarii, Rhizomucor pusillus, and Trametes sp. Enzyme extracts were produced in a practical inexpensive way. Synergistic effects on the extraction yield were observed when more than one enzyme extract was used. In addition, biotransformation of chlorogenic acid (ChA) by Aspergillus niger C23308 was studied. Equimolar transformation of ChA into CA and quinic acids (QA) was observed during the first 36 h in submerged culture. Subsequently, after 36 h, equimolar transformation of CA into protocatechuic acid was observed; this pathway is being reported for the first time for A. niger. QA was used as a carbon source by A. niger C23308. This study presents the potential of using CP to produce enzymes and compounds such as ChA with biological activities.

Commercial probiotic bacteria and prebiotic carbohydrates: a fundamental study on prebiotics uptake, antimicrobials production and inhibition of pathogens.

BACKGROUND Probiotics and prebiotics are among the most important functional food ingredients worldwide. The proven benefits of such ingredients to human health have encouraged the development of functional foods containing both probiotics and prebiotics. In this work, the production of antimicrobial compounds coupled to the uptake of commercial prebiotics by probiotic bacteria was investigated. RESULTS The probiotic bacteria studied were able to take up commercial prebiotic carbohydrates to the same or higher extent than that observed for lactose (control carbohydrate). The growth of probiotic bacteria was coupled to the production of antimicrobials such as short-chain fatty acids (SCFA), H2 O2 and bacteriocins. A higher production of antimicrobial compounds was recorded with Oligomate 55® compared with Regulact® and Frutafit® (3-5 and 10-115 times higher SCFA and H2 O2 production, respectively). The probiotic bacteria grown with Oligomate 55® also produced bacteriocins and other non-identified antimicrobial compounds. The antimicrobials produced by the probiotic bacteria inhibited up to 50% the growth of model pathogens such as Escherichia coli, Listeria innocua and Micrococcus luteus compared with control cultures. CONCLUSIONS The results here obtained are useful for the adequate selection of probiotic/prebiotics pairs and therefore in the development of efficient functional foods.

Degradation of α-Lactalbumin and β-Lactoglobulin by Actinidin

Susceptibility of the two major whey proteins, β-lactoglobulin and α-lactalbumin, to enzymatic degradation by actinidin as a function of pH and temperature was examined by a response surface methodology in order to elucidate the enzymatic action of the protease for controlled modification of these whey proteins. Pure whey protein fractions and commercial spray-dried whey were degraded by actinidin. The simultaneous effects of pH and temperature, in a range of 2.3 to 5 and 41 to 58°C respectively, on whey proteins degradation were studied, demonstrating a clear interrelationship between these two variables. With commercial whey, extended proteolysis of both β-lactoglobulin and α-lactalbumin was observed at pH 4.0 and temperature of 41.6°C; after an incubation time of 120 min, a degradation of 43.6% was obtained for the former, and 89.1% for the latter. Assays on pure proteins showed a complete degradation of α-lactalbumin and a 65.3% of degradation for β-lactoglobulin; therefore, the former appeared to be more susceptible to actinidin proteolysis.

Antihypertensive and antithrombotic activities of a commercial fermented milk product made with Lactobacillus casei Shirota and Streptococcus thermophilus

Peptides which inhibit the human angiotensin-converting enzyme (ACE) may be released during milk fermentation, and the micro-organisms or fermentation conditions influence the specific peptides produced. The aim of this study was to evaluate the ACE inhibitory and antithrombotic activities of a fermented milk product commercially available in Mexico. Viable cell numbers, protein hydrolysis and the pH remained constant during refrigerated storage. The IC50 of ACE inhibitory activity was 31.38 mg/mL. Eight peptide fractions exhibited ACE inhibitory activity and six showed antithrombotic activity. Two fractions showed both. This is the first time that both activities have been reported in a commercial probiotic product.

Role of Lysine ε-Amino Groups of β-Lactoglobulin on Its Activating Effect of Kluyveromyces lactis β-Galactosidase

Native beta-lactoglobulin binds and increases the activity of Kluyveromyces lactis beta-galactosidase. Construction of a three-dimensional (3D) model of beta-lactoglobulin showed that lysine residues 15, 47, 69, and 138 are the most exposed ones, thus the ones more likely to interact with beta-galactosidase. Molecular docking estimated the interaction energies of amino acid residues with either lactose or succinic anhydride, showing that Lys(138) is the most likely to react with both. Affinity chromatography demonstrated that succinylated beta-lactoglobulin diminished its ability to bind to the enzyme. Furthermore, when activity was measured in the presence of succinylated beta-lactoglobulin, its activating effect was lost. Since succinylation specifically blocks Lys epsilon-amino groups, their loss very likely causes the disappearance of the activating effect. Results show that the activating effect of beta-lactoglobulin on beta-galactosidase activity is due to the interaction between both proteins and that this interaction is very likely to occur through the Lys epsilon-amino groups of beta-lactoglobulin.

Effect of thermoultrasound on aflatoxin M 1 levels, physicochemical and microbiological properties of milk during storage

The aim of this research was to determine the physicochemical properties, microbial counts and aflatoxin M1 (AFM1) levels of thermoultrasonicated, pasteurized and untreated milk (control) at days 1, 7 and 14 of storage. Thermoultrasound treatment was performed at a rate of 20 kHz for 10 or 15 min and 95% amplitude on homogenized and non-homogenized milk samples. Results showed that most physicochemical parameters were within the Mexican norms established for milk. Ultrasound treatment for 15 min reduced solids precipitation (p < 0.05) in unhomogenized milk during storage as compared to the pasteurized milk. All samples complied with aerobic mesophilic counts limits set by the Mexican norm except the control and the homogenized milk sample which was thermoultrasonicated for 10 min. Enterobacteriaceae counts of pasteurized and 15 min-thermoultrasound homogenized milks complied with the norm. The lowest levels of AFM1 were found in the 10 min-thermoultrasound unhomogenized milk (0.15 ± 0.05 pg AFM⁠1E/mL) one day after storage. Thermoultrasound did not affect the color of samples but homogenized milk treated for 10 min exhibited less total color difference. A high phenolic content was found in thermoultrasound and pasteurized milks on day 1. Thermoultrasound could be an alternative to milk pasteurization that preserves the physicochemical and microbiological quality of milk while reducing AFM1 levels.