Determination of effective diffusion coefficient of immobilized Baker's yeast invertase in various concentration of PVA-alginate matrix

Baker's yeast invertase is immobilized in PVA-alginate matrix using an improved method. PVA beads were prepared by adding calcium alginate to improve its stability, mechanical and chemical properties. Boric acid was used as the cross-linking agent and additional chemicals consisting of 10% boric acid and sodium sulphate solution was used as a treatment solution to harden the PVA-alginate beads. The determination of the effective diffusion of PVA-alginate matrix the vital step in optimizing the preparation of immobilized and water-soluble biocatalyst. In this study the two-level full factorial design was used to investigate the effect of PVA and boric acid concentrations and diffusions coefficient. Diffusion coefficient (De) is one of the factors that significantly affect the mass transport within the immobilization matrix. De value varies for each concentration of PVA and boric acid. The result concluded that both factors significantly affect the De. A maximum De value of 5.0141 x 10(-5) cm2s-1 was obtained at boric acid and PVA concentraion of 7w/v and 10.5 w/v respectively

Isolation and characterization of polyhydroxyalkanoates (PHAS) producing bacteria from brackish stream

Polyhydroxyalkanoates (PHAs) are biopolymers which have similar characteristics with petrochemical plastics but a step better due to its biodegradable property. A total of 23 strains were isolated from two different brackish sources. In order to detect the PHAs granules, the PHAs producing bacteria were first screened with Sudan Black B staining. Twenty strains were observed with lipid granules and were subjected to further confirmation with Nile blue staining. From the Nile blue staining, only 10 strains have the ability in producing PHAs and 2 were identified as strong PHAs producers. This study focuses on the 2 strains named S1 and L1. Further identification procedure was carried out and found that strain S1 and L1 belongs to Pseudomonas sp. L1 strain was found to be promising for PHAs production since it accumulated PHAs for about 88.3%. The PHAs produced by this strain was analyzed using Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR) analysis and was identified as poly-3-hydroxybutyrate (P-3HB)

A study of frequency and pulses for stepper motor controller system by using programmable logic controller

The stepper motor movement process produced different frequency and pulses. This research explained about the frequency and pulses for the stepper motor movement by using Programmable Logic Controller (PLC) as research method. The study was done to find the suitable frequency and pulses for stepper motor movement by developing a prototype stepper motor controller system. The pulse frequency used did not affected the distance of moving load in the stepper motor operations. The increasing number of pulse frequency only will affect the time taken for the stepper motor to complete its operations. The result showed that number of pulse frequency at high operation was 5000 Hz. Pulse number reacted as a manipulated variable that affected both factor which is time taken of stepper motor operation and the distance of moving load

Development of cooling necklace system using vortex tube

A vortex tube is an intriguing, simple system capable of producing cold and hot streams at room temperature from a single compressed fluid supply. It is commonly used as a cooling system in many industrial applications because of its remarkable cooling capability and simplicity with no moving parts. This vortex tube does not need any refrigerants or chemical fluids to function as intended as a cooling device. The usage of the vortex tube as a cooling device that has been implemented in a cooling necklace has less to no substantial research data. Therefore, it is hard to determine the best possible outcome that could be achieved by integrating the vortex tube with a cooling necklace. Thus, the main objectives for this research are to determine the performance of vortex tube as a cooling device on a cooling jacket at different cold mass fraction and also to determine the performance of vortex tube as a cooling device on a cooling jacket at different inlet pressure. In this particular research, an experimental study was conducted in two different situational environments, one in a controlled environment which is indoors while the other is outdoors with direct sunlight to simulate real-life situations where the cooling necklace might be used. It can be concluded that cold mass fraction of 0.4 and the highest inlet pressure of 0.4 MPa are the optimum values to obtain the lowest temperature inside of the cooling jacket

Bioprocess optimization for pectinase production using Aspergillus niger in a submerged cultivation system

Background: Pectinase enzymes present a high priced category of microbial enzymes with many potential applications in various food and oil industries and an estimated market share of $ 41.4 billion by 2020. Results: The production medium was first optimized using a statistical optimization approach to increase pectinase production. A maximal enzyme concentration of 76.35 U/mL (a 2.8-fold increase compared with the initial medium) was produced in a medium composed of (g/L): pectin, 32.22; (NH4)2SO4, 4.33; K2HPO4, 1.36; MgSO4.5H2O, 0.05; KCl, 0.05; and FeSO4.5H2O, 0.10. The cultivations were then carried out in a 16-L stirred tank bioreactor in both batch and fed-batch modes to improve enzyme production, which is an important step for bioprocess industrialization. Controlling the pH at 5.5 during cultivation yielded a pectinase production of 109.63 U/mL, which was about 10% higher than the uncontrolled pH culture. Furthermore, fed-batch cultivation using sucrose as a feeding substrate with a rate of 2 g/L/h increased the enzyme production up to 450 U/mL after 126 h. Conclusions: Statistical medium optimization improved volumetric pectinase productivity by about 2.8 folds. Scaling-up the production process in 16-L semi-industrial stirred tank bioreactor under controlled pH further enhanced pectinase production by about 4-folds. Finally, bioreactor fed-batch cultivation using constant carbon source feeding increased maximal volumetric enzyme production by about 16.5-folds from the initial starting conditions

CO2 reforming of CH4 over Ni/SBA-15: Influence of Ni-loading methods

A series of Ni/SBA-15 catalysts were prepared with three different methods which are impregnation (IM), ion exchange (IE) and physical mixing (PM) for CO2 reforming of CH4. The XRD, BET, FTIR and TGA analyses showed that the quantity of Ni-support interaction (Ni-O-Si) by substitution of the OH with Ni species followed the order of Ni/SBA-15(IE) > Ni/SBA-15(IM) > Ni/SBA-15(PM), while the size of Ni particles and blockage of the pores increased with the order of Ni/SBA-15(IE) Ni/SBA-15(PM), while the stability of catalysts followed the order of Ni/SBA-15(IE) > Ni/SBA-15(IM) > Ni/SBA-15(PM). The excellent performance of Ni/SBA-15(IE) was related with the higher formation of Ni-support interaction, which altered the properties of catalyst towards an excellent catalytic performance. Meanwhile, the lowest activity of Ni/SBA-15(PM) was related with the higher agglomeration of Ni particles that were decorating on the surface part of SBA-15 arose from the weaker Ni-support interaction. This study provides new perspectives on the Ni-based catalyst, particularly on the influence of Ni-loading methods on the properties and catalytic performance of Ni/SBA-15 towards CO2 reforming of CH4

Malaysian politicians’ connection pattern on twitter using sna: a case of Najib Razak

Najib Razak is one of the most prominent politicians in Malaysia whose popularity has risen worldwide over the years due to his political sharp-witted strategy and various political scandals. He is also identified as one of the most followed Malaysian politicians on social media, especially Twitter. Hence, this study aims to apply Social Network Analysis (SNA) to further examine the interactions between Twitter users and the relationship formed with Najib Razak. A complete network of Najib Razak's Twitter account is used to study the connection pattern, influence, and groups developed between account users in the network. Netlytic is used to extract the data on Twitter, and based on the extracted dataset, it is discovered that 1004 nodes that represent Twitter users, follows and mentions the @najibrazak Twitter account. The dataset was further analyzed using R to explore the interaction and the connection patterns were visualized using Gephi. Based on the findings, the connectivity, centrality and clustering of the top 10 most influential Twitter users that contribute to the discussion and mention of Najib Razak on Twitter were determined. The previous work using Najib Razak's twitter account focused on finding the relations between public and politicians by analyzing the issues discussed through language processing at topical and lexical level. Unlike the previous achievement, the results from this proposed SNA technique can be further analyzed to gather greater insights on the hidden relationship built between politicians to strengthen their position and distinguish their possible future followers for further investigations

The impact of transglutaminase on soy protein and tofu texture

The enzyme transglutaminase was investigated for its cross-linking effect on the soy proteins of tofu. In vitro incubations confirmed that soy proteins are excellent substrates for transglutaminase, especially when denatured. The macroscopic effects resulting from the addition of transglutaminase were compared to changes at the microstructural and molecular level. Treatment produced a firmer tofu, with a significantly increased fracture force. Examination by SEM showed a change in the matrix structure, with transglutaminase resulting in a finer-stranded, uniform network that accounted for the increase in fracture force. At the molecular level, little, if any, cross-linking occurred within the tofu matrix in situ. This suggests that the change in functional properties afforded by addition of transglutaminase to tofu is due to a side reaction of the enzyme, for example hydrolysis of glutamine residues, rather than its cross-linking activity. These ideas are further explored in the accompanying paper

Heat transfer and electrical discharge of hybrid nanofluid coolants in a fuel cell cooling channel application

Hybrid nanofluid coolants is a new approach for advanced thermal management of Polymer Electrolyte Membrane fuel cells. Due to the high electrical conductivity of nanofluids, electrical discharge when a nanofluid coolant is used in a fuel cell is a concern and needs to be fundamentally studied. The objective is to obtain experimental correlations between heat transfer and electrical discharge rates of a nanofluid coolant in the form of a novel electro-thermal transfer ratio as a reference for future progress. A hybrid of 1%v TiO2 and SiO2 nanoparticles dispersed in a water and ethylene glycol (40:60) base fluid mixture was tested. The heated surface temperatures of the cooling channel were at 60 °C and 70 °C while the electrical power was nominally discharged through the test section at 0.7 V and 3 A. Under laminar flow, the concurrent changes to the temperature profile and active current were observed. The cooling was improved for the 40:60 hybrid TiO2:SiO2 nanofluid coolant with an enhancement factor of up to 2 times while the measured electrical current was visibly lower than the nominal current. The electro-thermal transfer ratio reduced exponentially with Reynolds number, indicating that electrical discharge strength into the coolant reduced at higher flow rates compared to the rate of heat transfer. These preliminary findings provide a new improved perspective in the assessment of nanofluid coolants for fuel cell systems and electrically-active systems in general