Ultrasonication of Micellar Casein Concentrate to Reduce Viscosity-Role of Undissolved Material.

This research reveals the underlying mechanisms that make high-intensity ultrasound an effective tool to reduce the viscosity of micellar casein concentrates and to enhance the solubility of the respective powders. Micellar casein concentrates (MCC) gained great importance in the production of valuable food products with high protein content, but the processing properties of the reconstituted solutions are deficient. Even though several presumptions were established, the reasons why ultrasound is able to reduce the product viscosity and what limitations occur when using sonication technology are still not clear yet. Our study aims to investigate those reasons by combining analyses of viscosity measurements, particle size distributions, solubility, and hydration. The data presented demonstrate that undissolved, highly hydrated particles play an important role in micellar casein concentrates showing a high viscosity. We conclude on the high voluminosity of those particles, since improved solubility and decreased viscosity are accompanying effects. The determined voluminosities of those particles are 35-40% higher than for colloidal dissolved micelles. Hence, the viscosity reduction of up to 50% can be only obtained by sonicating micellar casein concentrates derived from powder reconstitution, whereas ultrasonication of freshly prepared membrane-filtrated MCC does not reduce viscosity.

Retrospective Review of Multitarget Stool DNA as a Screening Test for Colorectal Cancer.

OBJECTIVES: To review the effectiveness of noninvasive multitarget stool DNA testing as a screening test for colorectal cancer. METHODS: We performed a retrospective review of patients referred to 2 high volume outpatient procedural centers for colonoscopy for positive Cologuard test. Positive findings for colorectal cancer based on pathologic findings and also advanced adenomas were recorded. Positive predictive value (PPV) was assessed. RESULTS: Of the 1585 patients evaluated and referred for colonoscopy from January 1, 2018 to November 1, 2019, for ICD-10 codes R19.5 (other fecal abnormalities) and K92.1 (melena), 84 were referred for a positive Cologuard test. Out of the 84, 6 were excluded based on family history of colon cancer in first degree relative or personal history of inflammatory bowel disease. Of the remaining 78 patients, 1 patient (1.3%) had colorectal cancer and 5 (6.4%) had advanced adenomas (>1 cm size, high grade dysplasia or villous). Postive predictive value for colorectal cancer was 1.3% and for precancerous lesions plus colorectal cancer was 7.7%. A total of 53 (68.0%) patients had either totally normal colonoscopy or hyperplastic polyps. Out of the 78 individuals in our study, 70 (89.7%) had normal findings, hyperplastic polyps, or non-advanced adenomas. CONCLUSIONS: Multitarget stool DNA testing carries an unacceptably low PPV to be utilized as a screening test for colorectal cancer. The study fails to detect both adenomas and colon cancer at a higher rate than screening colonoscopy in selected studies. The advantage of being noninvasive has been noted to increase colorectal cancer screening in otherwise non-compliant Medicare patients.

Characterization of bitter peptides in casein hydrolysates using comprehensive two-dimensional liquid chromatography.

Casein hydrolysates are important additives to foods for elderly and sports nutrition. However, due to the enzymatic generation of so-called bitter peptides, their application is limited. Therefore, the procedure needs to be optimized in order to restrict their occurrence. For this, extensive sensory evaluations are necessary. By combining two separation techniques using comprehensive two-dimensional liquid chromatography, we present a novel method for estimating the bitter taste of hydrolysate samples on the basis of their elution pattern. Using a size exclusion column in the first and a reversed phase column in the second dimension allows for a detailed sample evaluation regarding peptide size and relative hydrophobicity. The results obtained for different casein hydrolysates were correlated with the sensory evaluation. We found that hydrolysates with increasing bitterness contain a higher amount of peptides of high hydrophobicity and a molecular weight less than 6.5 kDa.

Neuroendocrine carcinoma of the ampulla of Vater: a case report, review and recommendations.

Neuroendocrine tumor (NET) of the ampulla of Vater is a rare presentation of biliary obstruction. Here, we present a case of NET and discuss the current recommendations that necessitate different management and surgical treatment than other sites. A 56-year-old Caucasian female presented with 2 years of right upper quadrant pain. Workup revealed a well-differentiated 2.2 cm NET at the ampulla with 0 MF/10 HPF, Stage 1A T2NOMO. Whipple procedure performed with 2.2 cm ampullary NET with 1 of the 15 lymph node metastases and <2 mitoses in 10 HPF. TNM classification: Stage IV T2N1MO. Regardless of tumor size, NETs metastasize in half of cases. Local excisions including endoscopic and laparoscopic ampullectomy were recommended only for poor surgical candidates. Ampullary NETs behave more aggressively than nonampullary NETs and their biological behaviors are irrespective of size. For patients of acceptable surgical risk, we recommend radical resection utilizing Whipple procedure.

Effect of glucose depletion during the synthesis of galactooligosaccharides using a trienzymatic system.

In this study the effect of glucose depletion using glucose oxidase and catalase, simultaneously to the synthesis of prebiotic galactooligosaccharides (GOS) by ß-galactosidase was studied. Considering total GOS yield, a strong dependency on the source of ß-galactosidase was found. Using an Aspergillus oryzae lactase, a small increase in GOS yield (from 50.0 ± 1.3 g/L to 54.1 ± 1.9 g/L) was noted. Due to the decreased rate of GOS disaccharide formation by the Kluyveromyces lactis enzyme, the total GOS yield was diminished (from 47.4 ± 0.1 g/L to 30.5 ± 1.7 g/L). However, for both enzymes, the synthesis of GOS tri- and higher oligosaccharides increased. Additionally, the total sugar content, and thus caloric value, of the final product was reduced, also resulting in a more purified GOS mixture.

Combination of two ß-galactosidases during the synthesis of galactooligosaccharides may enhance yield and structural diversity.

In this study, the combination of two ß-galactosidases to synthesize prebiotic galactooligosaccharides (GOS) was evaluated in terms of total GOS yield as well as GOS structures (chain length). Two different combinations of either Aspergillus oryzae and Cryptococcus laurentii or Aspergillus oryzae and Kluyveromyces lactis were tested to examine the influence of enzyme origin. Neither consecutive nor simultaneous synthesis with A. oryzae and C. laurentii led to an increased GOS yield. However, with the latter, synthesis of higher GOS (≥3 monomer units) was enhanced from 38.5% to 40% with special emphasis of tetra- and pentasaccharides, which increased from 6.7% to 12.8% and from 0.4% to 3.3%, respectively. Additionally, due to the different preferences of the two ß-galactosidases in terms of types of glycosidic linkages, the structural diversity of the final GOS product could be increased. Using K. lactis following the synthesis with A. oryzae increased the yield of total GOS from 24.6% to 33.1%, which was mainly due to the formation of GOS disaccharides. On the other hand, applying A. oryzae as the second enzyme led to a degradation of di- and trisaccharides, and thus total GOS yield was diminished, although the yield of tetrasaccharides could be enhanced. In conclusion, with both studied enzyme combinations it was possible to increase the percentage of higher GOS and reduce the residual lactose content of the final mixture, which is beneficial for subsequent purification processes. Thus, using more than one ß-galactosidase during the synthesis of GOS represents an interesting research area, which should be explored in more detail in the future.

Synthesis of Galactooligosaccharides in Milk and Whey: A Review.

Galactooligosaccharides (GOS) are synthesized by the enzyme ß-galactosidase during the hydrolysis of lactose. In this so-called transgalactosylation reaction the galactosyl moiety is transferred to another sugar molecule instead of water resulting in oligosaccharides of different chain lengths and glycosidic linkages. Because their structures are similar to oligosaccharides present in human breast milk, they act as prebiotics, which has been shown for infants and adults to be alike. While so far most of the research to maximize GOS yield has been carried out using buffered lactose solution as a starting material, more and more work is now conducted with dairy by-products such as whey and whey permeate, or even milk, for direct GOS synthesis in order to develop new GOS-enriched dairy products. This review aims to summarize the results obtained with various dairy liquids, and it rates their suitabilities to act as raw material for GOS production. Most of the studies using whey or milk have been carried out with enzymes from Aspergillus oryzae, Kluyveromyces lactis, Bacillus circulans, Streptococcus thermophilus, and several Lactobacillus species. As the initial lactose concentration (ILC) is known to be a crucial factor for high GOS yield, most of the research has been done with concentrated or supplemented milk and whey. However, a clear dependency on ILC could only be observed for the A. oryzae lactase, indicating a strong influence of milk components like minerals and proteins on the transfer activities of most enzymes.

Optimization of production, purification and lyophilisation of cellobiose dehydrogenase by Sclerotium rolfsii.

BACKGROUND: The enzyme cellobiose dehydrogenase (CDH) can be used to oxidize lactose to lactobionic acid. As Sclerotium rolfsii is known to be a good producer of CDH, the aim of this paper was to simplify its production and secondly to systematically study its purification aiming for a high yield. Two preservation methods (freezing and freeze-drying) and the influence of several protectants were investigated. RESULTS: Production of cellobiose dehydrogenase was optimized leading to a more simplified medium composition. Purification of the enzyme was evaluated by determining breakthrough profiles on different ion exchange (IEX) and hydrophobic interaction (HIC) materials with regard to buffer composition. Highest purification with an acceptable loss during the capture step using IEX was obtained with a Q Sepharose XL medium and a 100 mM sodium acetate buffer at pH 4.5. Subsequent purification using hydrophobic interaction chromatography was done at 1.1 M ammonium sulfate concentration. Purification was moderate, yielding a specific activity of 11.9 U/mg (56% yield). However, as could be shown in a preliminary experiment, purity of the obtained enzyme solution was sufficient for its intended use to oxidize lactose to lactobionic acid. Various sugars and sugar alcohols were investigated to study their protective effect during lyophilisation and freezing at -20 °C. Glucose and lactulose could be identified to have a high lyoprotective effect while loss of enzyme activity was high (77%) when using no additives. CONCLUSION: By simplifying the cultivation medium of Sclerotium rolfsii, the costs of cellobiose dehydrogenase production could be reduced. Simultaneously, CDH production was increased by 21%. The production of lactobionic acid from lactose is possible using partially purified and unpurified enzyme. Storage at -20 °C using 50% (w/v) glycerol was considered to be most suited for preservation of the enzyme.

Flow velocities after carotid artery stenting: impact of stent design. A fluid dynamics study in a carotid artery model with laser Doppler anemometry.

PURPOSE: To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model. METHODS: Three different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract. The membrane consists of a biocompatible silicone-polyurethane copolymer (Elast-Eon) with a pore size of 100 mum. All stents were deployed across the bifurcation and the external carotid artery origin. Flow velocity measurements were performed with laser Doppler anemometry (LDA), using pulsatile flow conditions (Re = 220; flow 0.39 l/min; flow rate ratio ICA:ECA = 70:30) in hemodynamically relevant cross-sections. The hemodynamic changes were analyzed by comparing velocity fluctuations of corresponding flow profiles. RESULTS: The flow rate ratio ICA:ECA shifted significantly from 70/30 to 73.9/26.1 in the MembraX and remained nearly unchanged in the SelfX and Wallstent. There were no changes in the flow patterns at the inflow proximal to the stents. In the stent no relevant changes were found in the SelfX. In the Wallstent the separation zone shifted from the orifice of the ICA to the distal end of the stent. Four millimeters distal to the SelfX and the Wallstent the flow profile returned to normal. In the MembraX an increase in the central slipstreams was found with creation of a flow separation distal to the stent. With a modification of the membrane this flow separation vanished. In the ECA flow disturbances were seen at the inner wall distal to the stent struts in the SelfX and the Wallstent. With the MembraX a calming of flow could be observed in the ECA with a slight loss of flow volume. CONCLUSIONS: Stent placement across the carotid artery bifurcation induces alterations of the physiologic flow behavior. Depending on the stent design the flow alterations are located in different regions. All the stents tested were suitable for the carotid bifurcation. The MembraX prototype has shown promising hemodynamic properties ex vivo.