Microbial fuel cell-based sensor for Enterobacter sp. KBH6958 activity monitoring during hydrogen production: the effects of pH and glucose concentration

Journal of Applied Electrochemistry - A microbial fuel cell (MFC) is an electricity-generating device utilising electrochemically active microorganisms as biocatalysts. Using MFC as a biosensor to...     

Wettability Enhancement of SiCp in Cast A356/SiCp Composite Using Semisolid Process

The effects of SiCp treatment and magnesium addition on microstructural and mechanical properties of Al356/20 wt% SiCp semisolid composites were investigated. The results showed that cleaning and oxidizing of SiCp and addition of 1 wt% Mg resulted in improving wettability, incorporation, and uniform distribution of SiCp in A356 matrix. Consequently, the ultimate tensile strength (UTS) value increased by 19% and 32% when the SiC was treated and also when Mg was added, respectively, compared to as-received SiCp. In addition, hardness value increased from 69.7 HV in as-received SiCp to 94.8 HV after SiCp treatment and addition of Mg.     

Natural rubber/poly(ethylene‐co‐vinyl acetate)‐blend‐based nanocomposites

Natural rubber (NR)/poly(ethylene‐co‐vinyl acetate) (EVA) blend–clay nanocomposites were prepared and characterized. The blend nanocomposites were prepared through the melt mixing of NR/EVA in a ratio of 40/60 with various amounts of organoclay with an internal mixer followed by compression molding. X‐ray diffraction patterns revealed that the nanocomposites formed were intercalated. The formation of the intercalated nanocomposites was also indicated by transmission electron microscopy. Scanning electron microscopy, used to study the fractured surface morphology, showed that the distribution of the organoclay in the polymer matrix was homogeneous. The tensile modulus of the nanocomposites increased with an increase in the organoclay content. However, an increase in the organoclay content up to 5 phr did not affect the tensile strength, but the organoclay reduced this property when it was increased further. This study also indicated that a low silicate content dispersed in the blend matrix was capable of increasing the storage modulus of the material. The addition of the organoclay also increased the decomposition temperature of the NR/EVA blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 353–362, 2006     

A study of poly vinyl chloride / poly(butylene adipate-co-terephthalate) blends

Polymer blends were prepared by melt blending technique using poly vinyl chloride (PVC) and poly(butylene adipate-co-terephthalate) (PBAT). Different ratios of the blends were studied to investigate their mechanical, thermal and morphological properties. The FTIR spectrum indicated a slight increase of frequencies at C = O peak from 1714 to 1718 cm^-1 indicating a chemical interaction between C = O of PBAT and α-hydrogen of PVC. The tensile properties of PVC/PBAT blends highest at weight ratio of 50/50. The dynamic mechanical analysis (DMA) result proves that PVC and PBAT formed a miscible system with one glass transition temperature (T_g). The incorporation of PBAT results in a gradual decrease of the viscosity (loss modulus) and an increase of elasticity (storage modulus). The thermal properties of blend show the decomposition temperature of PVC in the blend decrease with the addition of PBAT. Scanning electron micrograph shows good interfacial adhesion on the tensile fractured surface of PVC/PBAT blend, which played important roles in enhancing the mechanical properties (strength and modulus).     

New polymeric membrane nanofiltration for succinate recovery: a comparative study

Bio-based succinic acid recovery from fermentation broth has remained a challenge in the separation industry due the presence of by-products with similar physicochemical properties. In this work, the selective separation of succinate from succinate model solutions and the actual fermentation broth were investigated using newly fabricated polyimide P84 (PI) nanofiltration (NF) membrane and compared with three types of commercial pressure filtration membranes namely NF1, NF2 and NF270. Results show that PI membrane demonstrated comparable inorganic salt rejections performance as the commercial NF membranes of 86% and 99% for NaCl and Na₂SO₄, respectively. However PI shows much lower surface roughness, beneficial in reducing the fouling effect. PI also demonstrated equivalent performance for succinate permeation flux and retention at high concentration as the commercial membranes. PI exhibited high succinate retention (95%) in actual fermentation broth, equivalent to the commercial membranes (92–99%) and also higher selectivity factor (SF) < 0.14 compared to the NF1 membrane, SF < 0.19. Thus the PI membrane could give better succinate recovery against other carboxylates in the fermentation broth than the commercial membranes.     

Microbial community analysis of mixed anaerobic microflora in suspended sludge of ASBR producing hydrogen from palm oil mill effluent

This study investigated the microbial community of an anaerobic sequencing batch reactor (ASBR) operating at mesophilic temperature under varying hydraulic retention times (HRTs) for evaluating optimal hydrogen production conditions, using palm oil mill effluent (POME) as substrate. POME sludge enriched by heat treatment with hydrogen-producing bacteria was used as inoculum and acclimated with the POME. The microbial community was determined by first isolating cultivable bacteria at each operating HRT and then using polymerase chain reaction (PCR). The PCR products were sequenced and sequence identification was performed using the BLAST algorithm and Genbank database. The findings revealed that about 50% of the isolates present were members of the genus Streptococcus, about 30% were Lactobacillus species and around 20% were identified as species of genus Clostridium. Scanning electron microscopy (SEM) analysis also confirmed the presence of spherical and rod-shaped microbial morphologies in the sludge samples of bioreactor during prolonged cultivation.     

Recent advances in reuse of waste material as substrate to produce biohydrogen by purple non-sulfur (PNS) bacteria

Hydrogen is the fuel of the future mainly due to its high conversion efficiency, recyclability and non-polluting nature. Biological hydrogen production processes, mostly mediated photosynthetic bacteria, are more favorable candidates for biological hydrogen production due to their high conversion efficiency and versatility in the substrates (including wastewater) they can utilize. The potential utilization of waste material is being investigated extensively with suitable bioprocess technologies for providing cheaper raw materials with simultaneous waste treatment and bioremediation. Thus, this review article summarizes the biohydrogen production metabolism of purple non-sulfur (PNS) bacteria and research works involving biohydrogen production using various wastes such as tofu wastewater, palm oil mill effluent, olive mill wastewater, brewery wastewater, etc. by photosynthetic PNS bacteria. Waste materials used, yields and rates are reviewed, together with a discussion of the economics and perspectives of biohydrogen production from waste materials.     

Hydrogen production using Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564)

Fermentative hydrogen production was carried out using Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564). This work investigates the effects of initial substrate concentration, initial medium pH, and temperature. The hydrogen yield was about 3.1 mol (mol glucose)⁻¹ when starting with an initial glucose concentration of 10 gl⁻¹ and initial a pH of 6.0 ± 0.2 at a temperature of 37 °C. The volume of hydrogen produced decreased when higher initial glucose concentrations were applied. The most suitable conditions for hydrogen production in a batch reactor were observed at initial pH 6.0 ± 0.2 and 37 °C.     

Investigation of Microstructure and Mechanical Properties of A335 P11 Main Steam Pipe in Stesen Janaelektrik Jambatan Connaught Power Plant,Malaysia

This study aimed at examining the mechanical property, hardness and microstructure of the main steam pipe in the waste heat boiler electric power plant to prevent any possible failure and determine its lifetime, reliability and efficiency. A used alloy steel main steam pipe with ASTM standard grade (ASTM A335 P11) and standard chemical composition (1.25Cr–0.5Mo) was taken from the waste heat boiler electric power plant, Tenaga Nasional Berhad, Connaught Bridge Power Station, Klang Selangor, Malaysia. Specimen from each critical point P1 (incoming from WHB1B) at 485 °C and 39 bar, P2 (incoming from WHB1A) at 485 °C and 39 bar, P3 (joint of WHB1A & WHB1B) at 110 °C and 65 bar and P4 (outgoing to ST1C) at 212 °C and 4 bar were cut for sample preparations. Microstrural spectra of all the samples revealed that all the points were being transformed from pearlite to spheroidite and critical point P3 (at 110 °C and 65 bar) contained cavities in its grain boundaries. Also, the results showed that the P3 (at 110 °C and 65 bar) had the highest ductility (34.17), Poisson’s ratio (0.2683), lowest yield strength (286.83 MPa) and lowest ultimate tensile strength (423.26 MPa) against other locations. Other critical points; P1 (at 485 °C and 39 bar), P2 (at 485 °C and 39 bar) and P4 (at 212 °C and 4 bar) showed the average of tensile properties which is slightly low compared to new pipe material due to stress and high temperature exposed in main steam pipe for a long period time with little increase in ductility. Hardness test showed that the critical point P3 (at 110 °C and 65 bar) possessed the lowest hardness strength value (140.7 HV) due to complex state of stress which assisted in modification of microstructure prematurely in comparison with other locations.