Masafumi Goto

Assessment of the factors contributing to the variations in microcystins biodegradability of the biofilms on a practical biological treatment facility

This study revealed the biotic and abiotic parameters driving the variations in microcystins (MCs) biodegradability of a practical biological treatment facility (BTF). Results showed that similar trends of seasonal variation were seen for microcystin-LR (MCLR) biodegradability of biofilms on the BTF and indigenous MCLR-degrader population, where both peaks co-occurred in October, following the peaks of natural MCLR concentration and water temperature observed in August. The lag period might be required for accumulation of MCLR-degraders and MCLR-degrading enzyme activity. The MCLR-degrader population was correlated to temperature, MCLR and chlorophyll-a concentration in water where the biofilms submerged, indicating that these abiotic and biotic parameters exerted direct and/or indirect influences on seasonal variation in MCLR-biodegradability. In comparison, no effect of other co-existing MCs on biodegradation of one MC was observed. However, proliferation of MC-degraders along biodegradation processes positively responded to total amount of MCs, suggesting that multiple MCs contributed additively to MC-degrader proliferation.

Recombinant protein expression of Moringa oleifera lectin in methylotrophic yeast as active coagulant for sustainable high turbid water treatment

The natural coagulant Moringa oleifera lectin (MoL) as cationic protein is a promising candidate in coagulation process of water treatment plant. Introducing the gene encoding MoL into a host, Pichia pastoris, to secrete soluble recombinant protein is assessed in this study. Initial screening using PCR confirmed the insertion of MoL gene, and SDS-PAGE analysis detected the MoL protein at 8 kDa. Cultured optimization showed the highest MoL protein at 520 mg/L was observed at 28 °C for 144 h of culturing by induction in 1% methanol. Approximately, 0.40 mg/mL of recombinant MoL protein showed 95 ± 2% turbidity removal of 1% kaolin suspension. In 0.1% kaolin suspension, the concentration of MoL at 10 μg/mL exhibits the highest turbidity reduction at 68 ± 1%. Thus, recombinant MoL protein from P. pastoris is an effective coagulant for water treatment.

Phenotypic and genetic characterization of multidrug-resistant Staphylococcus aureus in the tropics of Southeast Asia

Antibiotic resistance has become a major public health problem throughout the world. The presence of antibiotic-resistant bacteria such as Staphylococcus aureus and antibiotic resistance genes (ARGs) in hospital wastewater is a cause for great concern today. In this study, 276 Staph. aureus isolates were recovered from hospital wastewater samples in Malaysia. All of the isolates were screened for susceptibility to nine different classes of antibiotics: ampicillin, ciprofloxacin, gentamicin, kanamycin, erythromycin, vancomycin, trimethoprim and sulfamethoxazole, chloramphenicol, tetracycline and nalidixic acid. Screening tests showed that 100 % of Staph.aureus isolates exhibited resistance against kanamycin, vancomycin, trimethoprim and sulfamethoxazole and nalidixic acid. Additionally, 91, 87, 50, 43, 11 and 8.7 % of isolates showed resistance against erythromycin, gentamicin, ciprofloxacin, ampicillin, chloramphenicol and tetracycline, respectively. Based on these results, 100 % of isolates demonstrated multidrug-resistant (MDR) characteristics, displaying resistance against more than three classes of antibiotics. Of 276 isolates, nine exhibited resistance to more than nine classes of tested antibiotics; these were selected for antibiotic susceptibility testing and examined for the presence of conserved ARGs. Interestingly, a high percentage of the selected MDR Staph.aureus isolates did not contain conserved ARGs. These results indicate that non-conserved MDR gene elements may have already spread into the environment in the tropics of Southeast Asia, and unique resistance mechanisms against several antibiotics may have evolved due to stable, moderate temperatures that support growth of bacteria throughout the year.

Characterisation and Application of Diatomite in Water Treatment

Conventional drinking water treatments are often inapplicable in developing countries, due to its high cost, lack of unfitting infrastructures, and availability and side effects of chemicals. Diatomite is a sedimentary rock containing diatoms with fine frustules surrounding it. It is used in various industrial applications due to its unique physical and chemical properties. This study investigates the properties and effectiveness of refined diatomite obtained from China in water treatment. The refined diatomite has enhanced adsorption and purity. Diatomite was observed under the Field Emission Scanning Electron Microscope coupled with Energy-Dispersive X-ray (FESEM–EDX) to study on its characterization. It was then tested as a coagulant to treat a different range of artificial turbid water (kaolin suspension) from low to high turbidity. The jar test was conducted to determine the optimum dosage of diatomite for turbidity removal.

Molecular characterization of multi-drug resistant Escherichia coli isolates from tropical environments in Southeast Asia

The emergence of antibiotic resistance among multidrug-resistant (MDR) microbes is of growing concern, and threatens public health globally. A total of 129 Escherichia coli isolates were recovered from lowland aqueous environments near hospitals and medical service centers in the vicinity of Kuala Lumpur, Malaysia. Among the eleven antibacterial agents tested, the isolates were highly resistant to trimethoprim-sulfamethoxazole (83.7%) and nalidixic acid (71.3%) and moderately resistant to ampicillin and chloramphenicol (66.7%), tetracycline (65.1%), fosfomycin (57.4%), cefotaxime (57.4%), and ciprofloxacin (57.4%), while low resistance levels were found with aminoglycosides (kanamycin, 22.5%; gentamicin, 21.7%). The presence of relevant resistance determinants was evaluated, and the genotypic resistance determinants were as follows: sulfonamides (sulI, sulII, and sulIII), trimethoprim (dfrA1 and dfrA5), quinolones (qnrS), β-lactams (ampC and blaCTX-M), chloramphenicol (cmlA1 and cat2), tetracycline (tetA and tetM), fosfomycin (fosA and fosA3), and aminoglycosides (aphA1 and aacC2). Our data suggest that multidrug-resistant E. coli strains are ubiquitous in the aquatic systems of tropical countries and indicate that hospital wastewater may contribute to this phenomenon.

Characterization of musty odor-producing actinomycetes from tropics and effects of temperature on the production of musty odor compounds

Geosmin and 2-methylisoborneol (MIB) outbreaks in tropical water bodies, such as Southeast Asia, by actinomycetes have not yet been elucidated in detail. Six Streptomyces isolates from lowland environments in Malaysia were selected and evaluated for their odor production under different temperatures. The gene responsible for the production of geosmin, geoA, was detected in all isolates, while only two isolates harbored tpc, which is responsible for 2-MIB production. This result suggested that geosmin and 2-MIB synthesis pathway genes already existed in the environment in the Tropics of Southeast Asia. Furthermore, our isolates produced musty odor compounds at 30°C, and differences were observed in musty odor production between various temperatures. This result indicated the potential for odor episodes in water bodies of the tropical countries of Southeast Asia throughout the year due to the mean annual ambient temperature of 27°C in the lowlands.

Immobilization of Heavy Metals in Tannery Sludge by Subcritical Water Treatment

Waste sludge discharged from tannery industry is a potential source of environmental pollution due to the hazardous heavy metals (HMs) such as chromium, copper and led. Surface water and soil pollutions by these HMs as a result of improper treatment and disposal of tannery sludge have become a great health-hazard concern to the society.There are various immobilization techniques for HMs that have been proposed and/or are being practiced. The hydro-thermal treatment utilizing subcritical water (SCW) is one of the new technologies, which is regarded as environmentally friendly and sustainable. The SCW technology can stabilize and reduce the volume of organic sludge as well as immobilize HMs to reduce direct toxicity and the risk. The study investigates immobilization of HMs, which are contained in tannery sludge in high concentrations, under the SCW conditions by forming a particular crystalline mineral that captures HMs. Based upon the preliminary SCW treatment experiments, which were conducted at moderate temperature of up 280 °C and under the saturated pressure with amended silica and calcium, and leaching tests, it was observed that heavy metal concentrations in the leachate from tannery sludge decreased after the SCW treatment. This implies that the SCW treatment has a potential as an immobilization technology for HMs contained in tannery sludge. Experiments are currently being undertaken in order to optimize the SCW conditions and silica/calcium amendment ratio, to identify the mechanism of immobilization and to evaluate stability of the immobilized HMs.

Recovery of Nitrogen and Phosphorus from Microalgae by Subcritical Water

Sustainable energy supply and its security are the prime concern for the establishment of the low carbon society. Microalgal biomass produced by mass cultivation has a high potential as a renewable and sustainable energy resource that is a tangible alternative to fossil energy resource. Since a microalga fixes atmospheric carbon dioxide as organic matters such as lipids and carbohydrates as a result of photosynthesis, microalgal lipids are considered to be a carbon-neutral feedstock for fuel production. Number of previous studies have shown that microalgae can be utilized as the source of energy as well as of biologically active substances, supplements, food and feed. However, only a limited number of studies have been conducted on utilization of microalgal biomass itself, after extraction of useful substances, as the nutrients source for its mass cultivation, although it is necessary to establish an economically feasible process to recycle nutrients to the mass cultivation system of the microalga. Cost of nitrogen and phosphorus would be a substantial part of the running cost of such mass cultivation systems without a nutrients recycling process. The results from this experiments of the sub-critical water (SCW) process, which has been carried out at relatively moderate temperature conditions of up to 250 °C and under the saturation steam pressure, is found as an unique process that can possibly recover both lipids as the feedstock and water soluble nutrients, N and P, necessary for the mass-cultivation of microalga simultaneously in a single process. Further, the experiments were carried out to optimize the SCW operational conditions to maximize lipids and nutrients recovery from microalgal biomass. The preliminary experimental data imply that effective and energy-saving extraction of the both classes of products is possible by applying the SCW technology to the microalgal biomass.

Mathematical simulation to up-scale electrolysis for effective suppression of freshwater cyanobacteria

Electrolysis, originally applied for removal of various pollutants from water and wastewater, has been recently found to be successful in the suppression and removal of cyanobacteria in freshwaters. Existing studies addressed crucial operational parameters based on batch laboratory studies; however, only very few studies have projected this information for continuous process to up-scale for industrial application. Oxygen Productive Electrode (OPE), a new type of electrolysis unit, is recommended as pre-treatment of freshwaters polluted by cyanobacterial blooms prior to conventional water treatment process. In this study, the data on suppression rate of Aphanizomenon sp., a filamentous cyanobacteria, from prior experimental work were used to mathematically evaluate the effects of configuration of OPEs as a pre-treatment stage of a water treatment plant. As it was found, the single-stage batch OPE was observed to be less effective on filamentous cyanobacteria than on coccus and unicellular cyanobacteria, thus an engineering consideration was made to improve system efficiency by estimating the overall system efficiency when multiple OPEs were implemented in series in continuous operation at steady state.