Comparative Analysis of Antioxidative Activity of Flavonoids Using HPLC–ED and Photometric Assays

The present investigation reports on the application of a new antioxidant activity assay for the examination of flavonoids. It has been shown that the high-performance liquid chromatography with electrochemical detection (HPLC–ED) measurements allow to obtain additional information about the antioxidative properties of pure compounds by measuring their half-wave potential, the chromatographic peak height, and the product of the peak height and exponent of potential. In comparison to the classical electrochemical measurements, the HPLC–ED is characterized by a much smaller detection limit. The results were compared with the standard photometric measurement based on 1,1-diphenyl-2-picrylhydrazyl radicals. The possible antioxidant activity forecasting is also discussed.     

Colour in short-term thermo-mechanically densified veneer of various wood species

Effect of short-term thermo-mechanical (STTM) densification temperature and pressure on the surface colour of veneer of four wood species—alder (Alnus glutinosa Gaertn.), beech (Fagus sylvatica L.), birch (Betula verrucosa Ehrh.), and pine (Pinus sylvestris L.) as well as possible correlations among all determined colour parameters (L*, a*, b*, h, C* and ?E) were investigated. Veneer sheets were densified at temperatures of 100, 150 or 200 °C and pressures of 4, 8 or 12 MPa for 4 min. The results were compared with those of non-densified veneers. The colour change of the samples was evaluated by CIEL*a*b* and L*h*C* colour co-ordinate systems. The results indicated: the temperature and pressure of densification affected to a big extent the colour of the veneer samples, with the effect of densification temperature being more evident than that of pressure. After the densification process, the veneers darkened. Colour changes are most pronounced at the highest densification temperature of 200 °C and very small at the lower temperatures of 100 and 150 °C for all investigated wood species. The change in a* is more pronounced than the change in L* or b*. In general, alder and birch veneer samples are characterized by the highest values of total colour difference followed by pine and beech samples among the four species. The quadratic models can be used for the prediction of surface colour in the densification process. The results of this study indicate that it is possible to govern surface colouration of wood veneers during densification process on an industrial basis.     

Organic whey as a source of Lactobacillus strains with selected technological and antimicrobial properties

Twenty‐five strains, isolated from raw, non‐pasteurised, organic whey samples, were identified phenotypically and genotypically. Biochemical tests were performed, and enzyme profiles, antibiotic resistance and antimicrobial properties were investigated. Sixteen strains were identified as genus Lactobacillus. Based on 16S rDNA gene sequence, the strains were identified as Lb. plantarum and Lb. fermentum. All of the strains had β‐galactosidase activity, and some of them reduced nitrate content. All strains utilised carbohydrates. The tested strains were characterised by low or average lipolytic and esterolytic activity. Moreover, the strains showed low proteolytic activity which is advantageous for their use as starter cultures for foods with low protein content. Strains Lb. fermentum S20, SM1, SM3, S2R and Lb. plantarum SM5 produced harmful N‐acetyl‐β‐glucosaminidase; moreover, the strain S20 produced also β‐glucuronidase. None of the strains produced α‐chymotrypsin. In phenotypic studies, most of the test strains were susceptible to gentamicin, ampicillin, tetracycline, chloramphenicol, penicillin and erythromycin. Strains Lb. plantarum S1 and Lb. fermentum S4, S7, S8, S10, SM1 and SM3 did not possess any transfer resistance genes. Antagonistic activity of the culture LAB strains was assessed as high or moderate in relation to the indicator strains, with the greatest zones of inhibition for E.coli and the smallest for L. monocytogenes ATCC 15313. This study reveals that the LAB strains isolated from organic whey have high potential for food application. Some strains of species Lb. fermentum (S4, S7, S8, S10) have been identified as the best candidates.     

A survey on the incidence of Prototheca mastitis in dairy herds in Lublin province,Poland

Prototheca mastitis has recently become an emerging disease; although its incidence is increasing steadily, its epidemiology remains largely understudied. The aim of this work was to investigate the prevalence of Prototheca spp. in dairy cows and their environment in Lublin province, covering most of southeastern Poland. Between December 2015 and July 2016, a total of 172 milking cows from 10 dairy farms were inspected for mastitis using clinical examination and the California Mastitis Test (CMT). Quarter milk samples (QMS, n = 179) and body site swabs (n = 151) from CMT-positive cows were collected for microbiological culture. In addition, we evaluated QMS and body site swabs from 23 healthy cows, along with 91 environmental samples. Of 100 CMT-positive cows, 71 had at least one QMS positive for microbial growth. In 8 (11.3%) of these cows, originating from 7 dairy farms, Prototheca spp. were cultured. The average somatic cell count of the Prototheca-containing milk was 4.02 × 10⁶ cells/mL compared with 0.13 × 10⁶ cells/mL of the Prototheca-free milk (collected from control animals). No significant differences were observed between mastitis and control cows with respect to counts of total white blood cells, lymphocytes, neutrophils, and eosinophils. Half of the cows with Prototheca spp. in their milk did not yield the algae from other anatomical sites. Eight cows were negative for the presence of Prototheca spp. in their milk but positive for the algae in swabs from anatomical sites. Among the environmental sources that were positive for Prototheca growth were watering troughs, manure, feed, and mud. All (45) Prototheca isolates recovered in this study were subjected to species- and genotype-level molecular identification. All QMS and most of the animal swabs (90%) yielded Prototheca zopfii genotype (gen.) 2. Of the animal samples, P. zopfii gen. 1 and Prototheca blaschkeae were isolated only from feces and rectum. Environmental samples grew either P. zopfii gen. 2 (67%) or P. zopfii gen. 1 (33%). This study demonstrates that P. zopfii gen. 2 is the third most common pathogen of mastitis in cattle in southeast Poland, with an overall incidence of 4.6%. Finding Prototheca spp., including P. zopfii gen. 1 and 2 and P. blaschkeae, in stool and rectal swabs from healthy animals may suggest their role as nonpathogenic microflora of bovine gut.     

Chemical composition of the cell wall of probiotic and brewer’s yeast in response to cultivation medium with glycerol as a carbon source

The structure of cell wall of yeasts (genus Saccharomyces) is one of the factors that determine their health-promoting properties connected to the presence of β-glucans and mannoprotein. The aim of the study was to determine the influence of glycerol as a carbon source on structural polymers of cell wall (β-glucan and mannoprotein) of probiotic yeasts Saccharomyces cerevisiae var. boulardii and brewer’s yeasts S. cerevisiae R9. Significant increase of the percentage of polysaccharide content in the cell wall dry weight of S. cerevisiae R9 brewer’s yeasts was noted (in the range of 10–20 %) after cultivation in medium containing glycerol at a concentration of 2–5 % and pH 4.0. The highest content of carbohydrates in probiotic yeasts’ cell wall (58 %) was observed after cultivation in medium containing 3 % of glycerol and pH 5.0. The cell wall of probiotic yeasts was characterized by higher content of mannoprotein comparing with cell wall preparation of brewer’s yeasts S. cerevisiae R9 composed mainly of β-glucans. After cultivation in mediums with 2 and 3 % of glycerol, the cell of brewer’s yeasts contained the highest amount of β(1,3/1,6)-glucan in dry weight of the cell wall (about 36 %). Glycerol at a concentration of 3 and 5 % also intensified mannoprotein biosynthesis in cell wall of S. cerevisiae R9, approximating their content to those noted in the cells of probiotic yeasts (about 29 % (w/w) of dry weight of the cell wall) after cultivation in a medium of pH 5.0 containing 3 % of glycerol.     

Production of dihydroxyacetone from an aqueous solution of glycerol in the reaction catalyzed by an immobilized cell preparation of acetic acid bacteria Gluconobacter oxydans ATCC 621

Dihydroxyacetone (1,3-dihydroxy-2-propanone, DHA) is applied in the food and cosmetic industries as well as in pharmacy and medicine. It is produced as a result of incomplete oxidation of glycerol by acetic acid bacteria Gluconobacter oxydans. This reaction is catalyzed by PQQ-dependent membrane-bound glycerol dehydrogenase. The research developed a method of obtaining DHA by oxidation of a 3?% aqueous solution of glycerol (pH 7.5) at a temperature of 23?°C, with the only reaction biocatalyst being an immobilized cell preparation obtained from G. oxydans cells. After 5?days of the process, DHA concentration in the solution accounted for 27.2?g/L and the reaction efficiency for 94?%. After 4?days of the reaction run in culture media with pH 5.0, at a temperature of 28?°C, free or immobilized cells of G. oxydans produced on average 25?g of DHA/L at the reaction efficiency of 87?%.