Specificity studies of bacillus 1,3-1,4-beta-glucanases and application to glycosynthase-catalyzed transglycosylation

Bacillus 1,3-1,4-beta-glucanases hydrolyze 1,3-1,4-beta-gluco-oligosaccharides with a retaining mechanism. The binding-site cleft of these endoglycosidases is composed of six subsites (-4 to +2) of which subsite -3 makes the largest contribution to transition state stabilization. The specificity of this subsite is here analyzed for both glycosidase and glycosynthase activities in the wild-type and the nucleophile-less E134A mutant Bacillus licheniformis enzymes. A D-galactosyl residue on the nonreducing end of a trisaccharide substrate is accepted by the enzyme and binds at subsite -3 in the productive enzyme-substrate complex. The wild-type enzyme catalyzes the hydrolysis of the substrate Glcbeta4Glcbeta3GlcbetaMU (Glc=glucosyl, MU=4-methylumbelliferyl) with a k(cat)/K(M) value only 1.3-fold higher than for the Galbeta4Glcbeta3GlcbetaMU (Gal=galactosyl) substrate. The corresponding alpha-fluorides act as good donors for the glycosynthase condensation reaction with mono- and disaccharide acceptors catalyzed by the E134A mutant. Whereas self-condensation and elongation products are also obtained as minor compounds with the Glcbeta4Glcbeta3GlcalphaF donor, nearly quantitative yields of single condensation products are obtained with the Galbeta4Glcbeta3GlcalphaF donor, in which the axial configuration of the 4-OH group on the nonreducing end prevents self-condensation and elongation reactions.     

Wide-Area Crowd Counting: Multi-view Fusion Networks for Counting in Large Scenes

International Journal of Computer Vision - Crowd counting in single-view images has achieved outstanding performance on existing counting datasets. However, single-view counting is not applicable...     

A thermo-mechanical machining method for improving the accuracy and stability of the geometric shape of long low-rigidity shafts

Journal of Intelligent Manufacturing - The article presents a new thermo-mechanical machining method for the manufacture of long low-rigidity shafts which combines straightening and heat treatment...     

Application of averaged instantaneous power spectrum for diagnostics of machinery operating under non-stationary operational conditions

Vibration analysis of machines operating under non-stationary operational conditions requires special attention. This refers to the necessity of use of order tracking algorithms together with additional advanced signal processing methods, especially when faults indicators of interest are located in resonance frequency ranges.     

Physicochemical, microbiological and sensory profiles of fermented milk containing probiotic strains isolated from kefir

A two-strain starter culture containing Lactobacillus plantarum CIDCA 83114, a potential probiotic strain isolated from kefir grains, and Streptococcus thermophilus CIDCA 321 was tested for the preparation of a fermented milk product. Kluyveromyces marxianus CIDCA 8154, a yeast with immunomodulatory properties was included to formulate a three-strain starter culture. Supernatants of enterohaemorragic Escherichia coli, shiga-toxin-producing strain, along with a two-strain or a three-strain starter culture were included in the medium of Vero-cell surface cultures. The results demonstrated that these combinations of microorganisms antagonize the cytopathic action of shiga toxins. The cell concentration of Lb. plantarum did not decrease during fermentation, indicating that the viability of this strain was not affected by low pH, nor did the number of viable bacteria change during 21 days of storage in either fermented products. The number of viable yeasts increases during fermentation and storage. Trained assessors analyzed the general acceptability of fresh fermented milks and considered both acceptable. The milk fermented with the two-strain starter culture was considered acceptable after two week of storage, while the product fermented with the three-strain starter culture remained acceptable for less than one week. The main changes in sensory attributes detected by the trained panel were in sour taste, milky taste and also in fermented attributes. The correlation between different sensory attributes and acceptability indicated that the panel was positively influenced by milky attributes (taste, odour, and flavour) as well as the intensity of flavour. In conclusion, the two-strain starter culture would be the more promising alternative for inclusion of that potential probiotic lactobacillus in a fermented milk product.     

Microwave vacuum drying and puffing of the meat tissue - process analysis

Tenderization based on papain and microwave vacuum drying and puffing (MVDP) as well as adequate processing conditions enabled expansion of slices of the raw meat tissue. The main aim of the study was to use the response surface method and find the conditions of puffing that could maximize the expansion of meat during MVDP. The bound was set on the expansion: the most expanded puffings should be of good quality, including a desirable porous structure. The best combination of values of the MVDP process conditions (e.g., the initial moisture content in meat slices, microwave energy, and the vacuum absolute pressure) was found during experiments using the central composite design. The volume of slices puffed under these conditions was 1.60–1.78 times greater than the volume of slices before MVDP, and the sensory quality index remained acceptable. The research showed that pretreatment reduced the hardness of sample by over 25% and increased its crispiness, which was confirmed in cryo-scanning electron microscopy images.     

Composition of oregano essential oil (Origanum vulgare) as affected by drying method

The influence of the drying method on volatile compounds of Origanum vulgare was evaluated. The drying methods tested were convective (CD) at 60 °C and vacuum-microwave (VMD), as well as a combination of convective pre-drying and VM finish-drying (CPD–VMFD). The volatile compounds of fresh and dried oregano were extracted by steam-hydrodistillation and analyzed by GC–MS. Oregano drying kinetics was described by a simple exponential model for CD and CPD–VMFD, while VMD kinetics consisted of two periods: linear until a critical point and exponential beyond that point. Thirty-four compounds were tentatively identified, with carvacrol, thymol, and γ-terpinene, being the major components. The total volatiles concentration of fresh oregano (33.0 g kg⁻¹) decreased significantly during drying, independently of the method used (CD: 10.2 g kg⁻¹, CPD–VMFD: 13.1 g kg⁻¹, and VMD: 27.9 g kg⁻¹). The final conclusion was that VM dehydrated Polish oregano was of better aromatic quality than that dried using hot air.     

Studies on capillary waves generated by light pulses of Nd3+ - glass laser with ultrasonic Q-switch

In the paper some results of the studies on parameters of capillary waves generated in 18H2N4WA type steel by means of light pulses of Nd³⁺ - glass laser with ultrasonic modulation of Q-factor of the optical resonator have been presented.     

Effects of the spray drying conditions of chokeberry (Aronia melanocarpa L.) juice concentrate on the physicochemical properties of powders

A semi‐industrial spray drying process of chokeberry juice concentrate using maltodextrin was analysed. The influence of the content and dextrose equivalent (DE) of maltodextrin, inlet air temperature and rotary disc atomiser speed was studied on the physicochemical properties of the obtained powders. The size and structure of the powder particles, bulk density, moisture content, flowability, yield and total polyphenol content were analysed. An increase in carrier content from 50% to 70% caused a 4.9% increase in total polyphenol retention, better flowability (Hausner ratio decrease of 0.17) and greater yield of the powder (60%). An increase in the drying temperature (150–170 °C) caused larger particle size and improved powder flowability but also resulted in greater loss of total polyphenols. A decrease in rotary atomiser speed (11 000–15 000 rpm) had a moderate influence on particle size and improvement in flowability but had no effect on polyphenol retention. Changes in the DE (8–22) of maltodextrin as a carrier indicated a moderate growing dependence on particle size and worse flowability.     

Behaviour of Dietary Fibre Supplements During Bread Dough Development Evaluated Using Novel Farinograph Curve Analysis

A regression model composed of two sigmoid functions with variable asymptotes was developed and used to analyse the dietary fibre supplement behaviour during bread dough mixing. Using eight commercial dietary fibres of different botanical origin and model wheat starch-gluten flour, farinograph curves for fibre-flour blends and for the flour only were performed. After smoothing of the curves with the regression model, difference farinograms as the fibre supplementation effects were determined. The results showed that the difference farinograms had two peaks, whose shape was strongly differentiated by the studied supplements. The presence of both peaks allowed distinguishing two kinds of the rheological activity of each fibre supplement: weakening and strengthening of the consistency of bread dough during its development. The carrot, oat, cranberry, and cacao fibres exhibited dominance of strengthening over weakening action. While chokeberry, carob, apple, and flax fibres were characterised by dominance of weakening over strengthening action. The analysis of both position and height of the peaks in the difference farinogram can be also helpful for determination of hydration kinetics of the fibres used for bread supplementation.