No more cleaning up - Efficient lactic acid bacteria cell catalysts as a cost-efficient alternative to purified lactase enzymes.

ß-galactosidases, commonly referred to as lactases, are used for producing lactose-free dairy products. Lactases are usually purified from microbial sources, which is a costly process. Here, we explored the potential that lies in using whole cells of a food-grade dairy lactic acid bacterium, Streptococcus thermophilus, as a substitute for purified lactase. We found that S. thermophilus cells, when treated with the antimicrobial peptide nisin, were able to hydrolyze lactose efficiently. The rate of hydrolysis increased with temperature; however, above 50 °C, stability was compromised. Different S. thermophilus strains were tested, and the best candidate was able to hydrolyze 80% of the lactose in a 50 g/L solution in 4 h at 50 °C, using only 0.1 g/L cells (dry weight basis). We demonstrated that it was possible to grow the cell catalyst on dairy waste, and furthermore, that a cell-free supernatant of a culture of a nisin-producing Lactococcus lactis strain could be used instead of purified nisin, which reduced cost of use significantly. Finally, we tested the cell catalysts in milk, where lactose also was efficiently hydrolyzed. The method presented is natural and low-cost, and allows for production of clean-label and lactose-free dairy products without using commercial enzymes from recombinant microorganisms. KEY POINTS: • Nisin-permeabilized Streptococcus thermophilus cells can hydrolyze lactose efficiently. • A low-cost and more sustainable alternative to purified lactase enzymes. • Reduction of overall sugar content. • Clean-label production of lactose-free dairy products.

Free and Bound Phenolic Compound Content and Antioxidant Activity of Different Cultivated Blue Highland Barley Varieties from the Qinghai-Tibet Plateau.

In this study, the polyphenols composition and antioxidant properties of 12 blue highland barley varieties planted on the Qinghai-Tibet Plateau area were measured. The contents of the free, bound and total phenolic acids varied between 166.20-237.60, 170.10-240.75 and 336.29-453.94 mg of gallic acid equivalents per 100 g of dry weight (DW) blue highland barley grains, while the free and bound phenolic acids accounted for 50.09% and 49.91% of the total phenolic acids, respectively. The contents of the free, bound and total flavones varied among 20.61-25.59, 14.91-22.38 and 37.91-47.98 mg of catechin equivalents per 100 g of dry weight (DW) of blue highland barley grains, while the free and bound flavones accounted for 55.90% and 44.10% of the total flavones, respectively. The prominent phenolic compounds in the blue hulless barley grains were gallic acid, benzoic acid, syringic acid, 4-coumaric acid, naringenin, hesperidin, rutin, (+)-catechin and quercetin. Among these, protocatechuic acid, chlorogenic acid and (+)-catechin were the major phenolic compounds in the free phenolics extract. The most abundant bound phenolics were gallic acid, benzoic acid, syringic acid, 4-coumaric acid, benzoic acid, dimethoxybenzoic acid, naringenin, hesperidin, quercetin and rutin. The average contribution of the bound phenolic extract to the DPPH• free radical scavenging capacity was higher than 86%, that of free phenolic extract to the ABTS•+ free radical scavenging capacity was higher than 79%, and that of free phenolic (53%) to the FRAP antioxidant activity was equivalent to that of the bound phenol extract (47%). In addition, the planting environment exerts a very important influence on the polyphenol composition, content and antioxidant activity of blue highland barley. The correlation analysis showed that 2,4-hydroxybenzoic acid and protocatechuic acid were the main contributors to the DPPH• and ABTS•+ free radical scavenging capacity in the free phenolic extract, while chlorogenic acid, vanillic acid, ferulic acid and quercetin were the main contributors to the free radical scavenging capacity in the bound phenol extract. The study results show that the blue highland barley grains have rich phenolic compounds and high antioxidant activity, as well as significant varietal differences. The free and bound phenolic extracts in the blue hulless barley grains have an equivalent proportion in the total phenol, and co-exist in two forms. They can be used as a potential valuable source of natural antioxidants, and can aid in enhancing the development and daily consumption of foods relating to blue highland barley.

In vitro study of the carotenoid-cleavage enzyme from Staphylococcus pasteuri TS-82 revealed substrate specificities and generation of norisoprenoid flavors.

Reactions of a crude enzyme extracted from S. pasteuri TS-82 to cleave carbon-carbon bonds in bicyclic and monocyclic carotenoid substrates were investigated. Dependencies of enzyme activities on processing temperature and pH were investigated and non-volatile and volatile breakdown products were characterized. The crude enzyme showed a maximum activity with zeaxanthin, followed in decreasing order by ß-carotene, canthaxanthin, astaxanthin, and ß-apo-8'-carotenal. The optimum pH value of the enzyme was 3.0 for both bicyclic and monocyclic substrates, whereas the optimum temperature of the enzyme was substrate specific at 60°C for C40 carotenoids and 50°C for ß-apo-8'-carotenal. Liquid Chromatography-Mass Spectra (LC-MS) and Gas Chromatography- Mass Spectra (GC-MS) indicated that the crude enzyme was able to catalyze substrates with cleavage at 9-10 and 9'-10' double bonds with C13 norisoprenoids being the main volatile reaction products in each case. Astaxanthin is a major source for α,ß-dihydro-ß-ionone.

Oat ß-glucan increased ATPases activity and energy charge in small intestine of rats.

Dietary oat or oat products may potentially help to fight against high risk of cardiovascular diseases and ß-glucan in oat was considered as a central player. The present study aimed to investigate the effects of dietary oat whole meal or ß-glucan on insulin sensitivity and energy metabolism of rats. Rats were fed with control diet, oat whole meal based diet, or control diet with supplemented ß-glucan for 4 weeks. Oat whole meal and ß-glucan increased insulin sensitivity index. Interestingly, supplementation of oat whole meal or ß-glucan induced increases in intestinal Na(+)K(+)-ATPase activity, Ca(2+)Mg(2+)-ATPase activity, and energy charge, particularly in the distal part of small intestine (ileum). Furthermore, amounts of Bifidobacterium and Lactobacillus in colon contents were elevated by oat whole meal or ß-glucan. These findings provide an insight into that ß-glucan increased insulin sensitivity and benefited intestinal health.

[Application of near infrared spectral fingerprint technique in lamb meat origin traceability].

Near infrared spectra of 99 lamb meat samples from three pasturing areas and two farming areas of China were scanned and analyzed to seek a cheap, rapid and effective method for lamb meat origin traceability. Two chemometric methods including linear discriminant analysis based on principal component analysis (PCA+LDA) and partial least squares discriminant analysis (PLS-DA) were used to develop the discriminate models. It was showed that there were significantly differences among the lamb meat samples from five regions based on NIR spectra after second derivative (Savitzky-Golay, 9 point) and multiplicative scattering correction (MSC) transformation in the whole wavelength. The discrimination of two models was best for classification of pasturing area and farming area, with both correctly classified by 100%. The correct classification rate of samples from five different regions using PCA+LDA model was 91.2%, higher than using PLS-DA model (76.7%). These results demonstrate that near infrared reflectance spectroscopy (NIRS) combined with chemometric analysis can be used as an effective method to classify lamb meat according to its geographical origin.

Distribution of phenolic acids in different tissues of jujube and their antioxidant activity.

Free, esterified, glycosided, and insoluble-bound forms of eight phenolic acids in pulp, seed, and peel of jujube are separated and quantified by high performance liquid chromatography with electrochemical detection (HPLC-ECD). In the whole jujube, p-hydroxybenzoic and cinnamic acids are the most abundant phenolic acids. All quantified phenolic acids are mainly present in jujube peel. Phenolic acids in seed and peel are present in the insoluble-bound form, while, in pulp in the glycosided form, the glycosided and insoluble-bound phenolic acid fractions in jujube pulp represent the highest total phenolic content and the strongest antioxidant activity determined by DPPH and FRAP assays. Our results show that most phenolic compounds with antioxidant activity in different tissues of jujube are present as the glycosided and insoluble-bound forms.

Synthesis of three haptens for the class-specific immunoassay of O,O-dimethyl organophosphorus pesticides and effect of hapten heterology on immunoassay sensitivity.

A general and broad class-specific enzyme-linked immunosorbent assay was developed for the O,O-dimethyl organophosphorus pesticides, including malathion, dimethoate, phenthoate, phosmet, methidathion, fenitrothion, methyl parathion and fenthion. Three haptens with different spacer-arms were synthesized. The haptens were conjugated to bovine serum albumin (BSA) for immunogens and to ovalbumin (OVA) for coating antigens. Rabbits were immunized with the immunogens and six polyclonal antisera were produced and screened against each of the coating antigens using competitive indirect enzyme-linked immunosorbent assay for selecting the proper antiserum. The effect of hapten heterology on immunoassay sensitivity was also studied. The antibody-antigen combination with the most selectivity for malathion was further optimized and tested for tolerance to co-solvent, pH and ionic strength changes. The IC(50) values, under optimum conditions, were estimated to be 30.1microgL(-1)for malathion, 28.9microgL(-1) for dimethoate, 88.3microgL(-1) for phenthoate, 159.7microgL(-1) for phosmet, 191.7microgL(-1) for methidathion, 324.0microgL(-1) for fenitrothion, 483.9microgL(-1) for methyl parathion, and 788.9microgL(-1) for fenthion. Recoveries of malathion, dimethoate, phenthoate, phosmet and methidathion from fortified Chinese cabbage samples ranged between 77.1% and 104.7%. This assay can be used in monitoring studies for the multi-residue determination of O,O-dimethyl organophosphorus pesticides.