Isolation and Identification of Lactic Acid Bacteria from Fermented Red Dragon Fruit Juices

Abstract: Red dragon fruit or red pitaya is rich in potassium, fiber, and antioxidants. Its nutritional properties and unique flesh color have made it an attractive raw material of various types of food products and beverages including fermented beverages or enzyme drinks. In this study, phenotypic and genotypic methods were used to confirm the identity of lactic acid bacteria (LAB) appeared in fermented red dragon fruit (Hylocereus polyrhizus) beverages. A total of 21 isolates of LAB were isolated and characterized. They belonged to the genus of Enterococcus based on their biochemical characteristics. The isolates can be clustered into two groups by using the randomly amplified polymorphic DNA method. Nucleotide sequencing and restriction fragment length polymorphism of the 16S rRNA region suggested that they were either Enterococcus faecalis or Enterococcus durans. Practical Application: Current research revealed the use of biochemical analyses and molecular approaches to identify the microbial population particularly lactic acid bacteria from fermented red dragon fruit juices.     

Reaction of Sn-3.5Ag-0.7Cu-xSb solder with Cu metallization during reflow soldering

The influence of Sb on the growth kinetics of intermetallic compound (IMC) and chemical reaction between Sn-3.5Ag-0.7Cu-xSb (x=0, 0.2, 0.5, 1.0, 1.5, and 2.0) lead-free solder and Cu during reflow soldering is investigated in this study. Scanning electron microscope (SEM) is used to measure the thickness and grain size of the intermetallic layer and observe the microstructural evolution of solder joints. Results show that both thickness and grain size of IMC decrease once Sb is added into the Sn-Ag-Cu solder system, and have a significant drop at the composition of about 1.0 wt%. Beyond this composition, the thickness and grain size of IMC increase slightly. The growth exponents for both IMC layers and grains are determined by curve-fitting to study the growth kinetics of IMC in wetting reaction. The results reveal that the growth exponents of IMC range from 0.32 to 0.35, and those of IMC grains range from 0.28 to 0.32, which suggests that the growth of IMC is controlled through combined kinetic processes of atomic interdiffusion, interfacial reaction, and grain ripening. These data also show that Sn-3.5Ag-0.7Cu with about 1.0 wt% Sb solder system exhibits the smallest growth rate and gives the most prominent effect in retarding IMC growth and refining IMC grain size. Based on the phase diagram analysis and the observation of the microstructural evolution of the solder joints, a heterogeneous nucleation mechanism for retarding the IMC growth due to Sb addition is proposed.     

Effect of doping on single-walled carbon nanotubes network of different metallicity

Effects of doping on single-walled carbon nanotubes (SWNT) networks with different metallicity are reported through the study of sheet resistance changes upon annealing and acid treatment. SWNT film with high metallic tube content is found to have relatively good chemical stability against post treatments, as demonstrated from its stable film performance in ambient after annealing, and merely 15% reduction in sheet resistance upon sulfuric acid treatment. Conversely, film stability of SWNT film with low metallic content which comprises largely of semiconducting SWNT varies with days in ambient, and its sheet resistance changes drastically after treated with acid, indicating the extreme sensitivity of semiconducting SWNT to surrounding environment. The results suggest that annealing removes unintentional oxygen doping from the ambient and shifts the Fermi level towards the intrinsic Fermi level. Acid treatment, on the other hand, introduces physisorbed and chemisorbed oxygen and shifts the Fermi level away from the intrinsic level and increases the hole doping.     

The effect of mechanical grinding on the mesoporosity of steam‐activated palm kernel shell activated carbons

BACKGROUND: Palm kernel shell activated carbon (OPSA) produced by steam gasification at high temperatures generally results in high surface areas of 1146 to 1600 m² g^?1, attributed to the high volume of micropores (0.43 to 0.56 cm³ g^?1). The mesoporosity of naturally occurring activated carbons is observed to increase with decreasing particle size. Mechanical grinding was therefore performed to investigate its effect on the mesoporosity and microporosity of OPSA. RESULTS: Mechanical grinding had a strong effect on mesopore volume and average pore diameter, with an increase in mesopore volume from 47 to 66% as particle size decreases. Interestingly, no significant effect on the micropore fraction was observed in ground OPSA particles. CONCLUSIONS: The mechanically ground OPSA particles possessed dual adsorption capabilities due to the high microporosity and moderate mesoporosity contained in the structures. This results in interesting porosity behaviour of palm kernel shell activated carbons and the potential to provide materials of distinct sorption capacities with minimal treatment. Copyright © 2009 Society of Chemical Industry     

Enhancement of monoclonal antibody productivity by promoting active hypothermic growth in hybridoma cells

BACKGROUND: Many reports have suggested that mild hypothermic culture conditions improve the specific monoclonal antibody (mAb) productivity of mammalian cells. The effect of active hypothermic growth on the mAb productivity of the hybridoma C₂E₇ was investigated. Hybridoma growth under hypothermic conditions (32 °C) was stimulated by supplementation of the culture medium with high serum concentrations (up to 30%). RESULTS: Specific and volumetric mAb productivity of a stimulated, active growth, mildly hypothermic hybridoma culture (30% FBS supplemented, 32 °C) were 1.38‐ and 1.34‐fold greater than the control culture (10% FBS supplemented, 37 °C). The enhanced specific mAb productivity under hypothermic conditions was associated with an increase in IgM mRNA levels during both the lag and early exponential phases of hypothermic growth. CONCLUSION: Stimulation of hybridoma growth under mildly hypothermic conditions increased both the specific and volumetric mAb productivity of hybridoma cells. Copyright © 2009 Society of Chemical Industry     

Modelling driver behaviour towards innovative warning devices at railway level crossings

Improving safety at railway level crossings is costly and as funds are often limited, it is important to search for cost-effective, evidence-based solutions. The effect that the many existing alternative systems have on driver behaviour is not always known. This paper compares driver behaviour towards two novel warning devices (rumble strips and in-vehicle audio warning) at railway level crossings with two conventional warning devices (flashing light and stop sign). Regression models were developed to reflect driver's responses towards the four different types of devices based on data collected from a driving simulation experiment. The regression models include a binary choice model for predicting the probability of a driver stopping or driving through a railway crossing, as well as mixed regression models for predicting the moment at which a driver will produce specific behavioural responses before stopping at a crossing (e.g. initiation of accelerator release and application of foot-pedal brake). Violation results indicated the active systems produced much higher levels of driver compliance than passive devices. Contributing factors, such as age, gender, speed and types of warning devices were found significant at different approach stages to the level crossings. With the application of such behavioural models and traffic conflict techniques in microscopic simulation tools, traffic safety indicators, such as collision likelihood and time-to-collision can be estimated. From these, relative safety comparisons for the different traffic devices are derived.     

Fluorescent quantitation method for differentiating the nativity of green fluorescent protein

A gel imaging method was employed to quantitate the GFP that had been subjected to denaturation and degradation treatments. This method is able to differentiate the nativity of GFP by relating the observed changes in the position of fluorescent bands which is unable to be detected using the spectrofluorometric method.     

Display of the antigenic region of Nipah virus nucleocapsid protein on hepatitis B virus capsid

The C-terminal domain of Nipah virus (NiV) nucleocapsid protein (NP_401–532) was inserted at the N-terminus and the immunodominant loop of hepatitis B core antigen (HBc). The stability of NP_401–532 increased tremendously when displayed on the HBc particles. These particles reacted specifically with the swine anti-NiV and the human anti-HBc antisera.