Stability of β-glucosidase Activity Produced by Bifidobacterium and Lactobacillus spp. in Fermented Soymilk During Processing and Storage

ABSTRACT: Microorganisms possess endogenous enzymes, however the stability of these enzymes during storage in soymilk has not been studied. β-glucosidase is an important enzyme that could be used in the bioconversion of the predominant soy isoflavone glucosides to their bioactive aglycone forms. Fifteen probiotic microorganisms including bifidobacterium, Lactobacillus acidophilus , and Lactobacillus casei were screened for β-glucosidase activity using p-nitrophenyl-β-d-glucopyranoside as a substrate. Six strains were selected on the basis of β-glucosidase activity produced during fermentation of soymilk. The stability of the enzyme activity was assessed during incubation for up to 48 h and storage for 8 wk at frozen (-80°C), refrigerated (4°C), room (24.8°C), and incubation (37°C) temperatures. L. casei strains showed the highest β-glucosidase activity after 24 h of incubation followed by L. acidophilus strains, whereas bifidobacterium strains showedleast activity. However, p-glucosidase from Bifidobacterium animalis BB12 showed the best stability during the 48 h fermentation. Lower storage temperatures (-80°C and 4°C) showed significantly higher ( P < 0.05) β-glucosidase activity and better stability than that at higher temperatures (24.8°C and 37°C). The stability of β-glucosidase from these microorganisms should be considered for enzymic biotransformation during storage of isoflavone β-glucosides to bioactive isoflavone aglycone forms with potential health benefits.     

Yogurt can beneficially affect blood contributors of cardiovascular health status in hypertensive rats

Cardiovascular disease is the single leading cause of death in the world and elevated blood pressure is one of the major independent risk factors. Angiotensin-I-converting enzyme-inhibitors have received considerable attention for their effectiveness in both the prevention and the treatment of hypertension. To confirm the antihypertensive effect, the influence of yogurt- and probiotic yogurt-based diets on the weight gain, serum lipid profile, and blood pressure (BP) were investigated in spontaneously hypertensive rats (14 wk old). A total of 3 dietary treatments were fed for 8 wk: skim milk diet (Feed-C), skim milk diet supplemented with freeze dried low fat yogurt (Feed-Y), and with freeze dried low-fat probiotic yogurt (Feed-PY). The total weight gain for the 8-wk period was maximum in rats fed Feed-C (90 g) followed by those fed Feed-PY (85.7 g) and Feed-Y (78.7 g), indicating that the overall weight gains were lesser (statistically non-significant) in the groups fed yogurt containing diets. At the end of the feeding period the reduction in systolic BP of rats fed Feed-Y was 3.7% (-9.5 mm Hg) and 2.7% (-6.4 mm Hg) in those fed Feed-PY while reduction in diastolic BP was 30% (-9.4 mm Hg) and 44% (-13.8 mm Hg), respectively, in comparison to those fed Feed-C. The levels of total cholesterol and low density lipoprotein-cholesterol of rats fed the supplemented diets were lower than those fed Feed-C while no changes in the levels of high density lipoprotein-cholesterol were observed. It was concluded that feeding diets supplemented with yogurts exhibited antihypertensive and hypocholesterolemic effects in spontaneously hypertensive rats.     

Selective and differential enumerations of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium spp. in yoghurt--a review

Yoghurt is increasingly being used as a carrier of probiotic bacteria for their potential health benefits. To meet with a recommended level of ≥ 10⁶ viable cells/g of a product, assessment of viability of probiotic bacteria in market preparations is crucial. This requires a working method for selective enumeration of these probiotic bacteria and lactic acid bacteria in yoghurt such as Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lb. acidophilus, Lb. casei and Bifidobacterium. This chapter presents an overview of media that could be used for differential and selective enumerations of yoghurt bacteria. De Man Rogosa Sharpe agar containing fructose (MRSF), MRS agar pH 5.2 (MRS 5.2), reinforced clostridial prussian blue agar at pH 5.0 (RCPB 5.0) or reinforced clostridial agar at pH 5.3 (RCA 5.3) are suitable for enumeration of Lb. delbrueckii subsp. bulgaricus when the incubation is carried out at 45 °C for 72 h. S. thermophilus (ST) agar and M17 are recommended for selective enumeration of S. thermophilus. Selective enumeration of Lb. acidophilus in mixed culture could be made in Rogosa agar added with 5-bromo-4-chloro-3-indolyl-β-d-glucopyranoside (X-Glu) or MRS containing maltose (MRSM) and incubation in a 20% CO₂ atmosphere. Lb. casei could be selectively enumerated on specially formulated Lb. casei (LC) agar from products containing yoghurt starter bacteria (S. thermophilus and Lb. delbrueckii subsp. bulgaricus), Lb. acidophilus, Bifidobacterium spp. and Lb. casei. Bifidobacterium could be enumerated on MRS agar supplemented with nalidixic acid, paromomycin, neomycin sulphate and lithium chloride (MRS-NPNL) under anaerobic incubation at 37 °C for 72 h.     

Viability of Two Freeze-dried Strains of Bifidobacterium and of Commercial Preparations at Various Temperatures During Prolonged Storage

ABSTRACT: Viability of bifidobacteria in freeze-dried probiotic products at various temperatures during prolonged storage was assessed. Bifidobacterium longum 1941 and B. longum 536 were freeze-dried and capsules were manufactured. Five commercial probiotic capsule products were also tested. The capsules were stored at -18 °C, 4 °C, and 20 °C. Cell counts were enumerated using MRS-NNLP agar at 37 °C for 72 h under anaerobic conditions at 0, 1, 2, 5, and 8 mo (commercial capsules) and at 0, 1, 2, 5, 8, 11, 14, 17, and 20 mo (laboratory capsules). Storage at 20 °C showed the greatest decline in the viability of bifidobacteria, whereas that at -18 °C showed the least decrease.     

Chemical composition, in vitro cytotoxic and antioxidant activities of the essential oil and major constituents of Cymbopogon jawarancusa (Kashmir)

The chemical composition of the hydrodistillate of aerial parts of Cymbopogon jawarancusa, a natural grass considered as major forage for animal nutrition, used in food because of the presence of sufficient concentration of minerals like calcium and potassium was analysed by capillary GC–FID, GC–MS and ¹³C NMR. Seventeen constituents representing 97.8% of the total oil with piperitone (58.6%) and elemol (18.6%) as major constituents were identified. In vitro cytotoxicity of the oil and its constituents on human cancer cell lines THP-1 (leukemia), A-549 (lung), HEP-2 (liver) and IGR-OV-1 (ovary) was evaluated by Sulphorhodamine-B assay. The oil was found to be more potent than its components against cancer cell lines tested with IC₅₀ of 6.5 μg/ml (THP-1), 6.3 μg/ml (A-549), 7.2 μg/ml (HEP-2) and 34.4 μg/ml (IGR-OV-1). Antioxidant activity of oil and its constituents was evaluated by DPPH assay. In conclusion, the results demonstrate potent cytotoxic and antioxidant effects of oil, and its components like piperitone, α-pinene, β-caryophyllene and β-elemene.     

Interactions of fluoroquinolone antibacterial agents with aqueous chlorine: reaction kinetics, mechanisms, and transformation pathways

Kinetics, products, and mechanistic aspects of reactions between free available chlorine (HOCl/OCl-), ciprofloxacin (CF), and enrofloxacin (EF) were extensively investigated to elucidate the behavior of fluoroquinolone antibacterial agents during water chlorination processes. Although the molecular structures of these two substrates differ only with respect to degree of N(4) amine alkylation, CF and EF exhibit markedly different HOCl reaction kinetics and transformation pathways. HOCI reacts very rapidly at CF's secondary N(4) amine, forming a chloramine intermediate that spontaneously decays in aqueous solution by concerted piperazine fragmentation. In contrast, HOCl reacts relatively slowly at EF's tertiary N(4) amine, apparently forming a highly reactive chlorammonium intermediate (R3N-(4)Cl+) that can catalytically halogenate EF or other substrates present in solution. Flumequine, a fluoroquinolone that lacks the characteristic piperazine ring, exhibits no apparent reactivity toward HOCI but appears to undergo facile halodecarboxylation in the presence of R3N(4)-Cl+ species derived from EF. Measured reaction kinetics were validated in real water matrixes by modeling CF and EF losses in the presence of free chlorine residuals. Combined chlorine (CC) kinetics were determined under selected conditions to evaluate the potential significance of reactions with chloramines. CF's rapid kinetics in direct reactions with HOCl, and relatively high reactivity toward CC, indicate that secondary amine-containing fluoroquinolones should be readily transformed during chlorination of real waters, whether applied chlorine doses are present as free or combined residuals. However, EF's slower HOCl reaction kinetics, recalcitrance toward CC, and participation in the catalytic halogenation cycle described herein suggest that tertiary amine-containing fluoroquinolones will be comparatively stable during most full-scale water chlorination processes.     

Prevalence of antibiotic resistance genes in the bacterial flora of integrated fish farming environments of pakistan and Tanzania

The use of a wide variety of antimicrobials in human and veterinary medicine, including aquaculture, has led to the emergence of antibiotic resistant pathogens. In the present study, bacteria from water, sediments, and fish were collected from fish farms in Pakistan and Tanzania with no recorded history of antibiotic use. The isolates were screened for the presence of resistance genes against various antimicrobials used in aquaculture and animal husbandry. Resistant isolates selected by disk diffusion and genotyped by Southern hybridization were further screened by polymerase chain reaction (PCR) and amplicon sequencing. The prominent resistance genes identified encoded tetracycline [tetA(A) and tetA(G)], trimethoprim [dfrA1, dfrA5, dfrA7, dfrA12, and dfrA15], amoxicillin [bla(TEM)], streptomycin [strA-strB], chloramphenicol [cat-1], and erythromycin resistance [mefA]. The int1 gene was found in more than 30% of the bacterial isolates in association with gene cassettes. MAR indices ranged from 0.2 to 1. The bla(NDM-1) gene was not identified in ertapenem resistant isolates. It is hypothesized that integrated fish farming practices utilizing domestic farm and poultry waste along with antibiotic residues from animal husbandry may have contributed to a pool of resistance genes in the aquaculture systems studied.     

Prevalence and Distribution of Arcobacter spp. in Raw Milk and Retail Raw Beef

A total of 106 beef samples which consisted of local (n = 59) and imported (n = 47) beef and 180 milk samples from cows (n = 86) and goats (n = 94) were collected from Selangor, Malaysia. Overall, 30.2% (32 of 106) of beef samples were found positive for Arcobacter species. Imported beef was significantly more contaminated (46.80%) than local beef (16.9%). Arcobacter butzleri was the species isolated most frequently from imported (81.8%) and local (60%) beef, followed by Arcobacter cryaerophilus in local (33.3%) and imported (18.2%) beef samples. Only one local beef sample (10%) yielded Arcobacter skirrowii. Arcobacter species were detected from cow's milk (5.8%), with A. butzleri as the dominant species (60%), followed by A. cryaerophilus (40%), whereas none of the goat's milk samples were found positive for Arcobacter. This is the first report of the detection of Arcobacter in milk and beef in Malaysia.