Publications by authors named "Obulisamy P Karthikeyan"

Water crisis around the world leads to a growing interest in emerging contaminants (ECs) that can affect human health and the environment. Research showed that thousands of compounds from domestic consumers, such as endocrine disrupting chemicals (EDCs), personal care products (PCPs), and pharmaceuticals active compounds (PhAcs), could be found in wastewater in concentration mostly from ng L to μg L. However, generally, wastewater treatment plants (WWTPs) are not designed to remove these ECs from wastewater to their discharge levels.

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Plastic disposal and their degraded products in the environment are global concern due to its adverse effects and persistence in nature. To overcome plastic pollution and its impacts on environment, a sustainable bioplastic production using renewable feedstock's, such as algae, are envisioned. In this review, the production of polymer precursors such as polylactic acid, polyhydroxybutyrates, polyhydroxyalkanoates, agar, carrageenan and alginate from microalgae and macroalgae through direct conversion and fermentation routes are summarized and discussed.

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Article Synopsis
  • * Optimized conditions included a 12-hour day-night cycle, pH around 7.0 with aeration, which maximized biomass production and nutrient removal efficiency from the wastewater.
  • * Results suggested that this method could effectively use municipal wastewater to produce biofuels and other valuable products while improving environmental sustainability.
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Dehydrogenation of methanol (CHOH) into direct current (DC) in fuel cells can be a potential energy conversion technology. However, their development is currently hampered by the high cost of electrocatalysts based on platinum and palladium, slow kinetics, the formation of carbon monoxide intermediates, and the requirement for high temperatures. Here, we report the use of graphene layers (GL) for generating DC electricity from microbially driven methanol dehydrogenation on underlying copper (Cu) surfaces.

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Fibers come from natural and fossil resources and are an essential commodity widely used by textile industries. Considering current supply and future demands, the repurposing of agricultural residues into fibers is an eco-friendly, attractive option that might mitigate environmental pollution. In this review, we have summarized multiple alternate secondary sources for fiber production, with a case study using banana plant residual biomass, a common agricultural waste in many developing countries.

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  • The study focuses on improving biomass productivity in the microalgal strain sp. BDUG 100241 by testing different growth conditions: photoautotrophic, mixotrophic, and heterotrophic.
  • The best growth was observed in mixotrophic conditions with glucose, where the use of sodium acetate as a carbon source resulted in the highest biomass production and biomolecule accumulation.
  • Specifically, a sodium acetate concentration of 7.5 g/L yielded the highest biomass (2.40 g/L) and lipid content (53.50%), indicating it as the most effective organic carbon source for this strain.
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In present investigation, effect of diverting acidogenic off-gas from leached bed reactor (LBR) to up-flow anaerobic sludge blanket (UASB) reactor during semi-continuous food waste (FW) anaerobic digestion was evaluated. In test LBR headspace pressure (3.3 psi) was maintained with intermittent headspace gas transfer into UASB.

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Tolypothrix, a self-flocculating, fast growing, CO and nitrogen-fixing cyanobacterium, can be cultivated in nutrient-poor ash dam waters of coal-fired power stations, converting CO emissions into organic biomass. Therefore, the biomass of Tolypothrix sp. is a promising source for bio-fertiliser production, providing micro- and macronutrients.

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Manufacturing and resource industries are the key drivers for economic growth with a huge environmental cost (e.g. discharge of industrial effluents and post-mining substrates).

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Polyhydroxyalkanoates (PHAs) are group monomers/heteropolymers that are biodegradable and widely used in biomedical applications. They are considered as alternatives to fossil derived polymers and accumulated by microbes including extremophilic archaea as energy storage inclusions under nutrient limitations. The use of extremophilic archaea for PHA production is an economically viable option for conventional aerobic processes, but less is known about their pathways and PHA accumulation capacities.

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The reliance of fossil fuel for industrial and energy sectors has resulted in its depletion. Therefore, enormous efforts have been considered to move-out from fossil fuels to renewable energy sources based industrial process developments. Recently, biohydrogen (bio-H) has been recognised as a clean source of fuel with high-energy efficiency, which can be produced via different routes.

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This study aimed to characterize the biofilm microbial community that causes corrosion of API 5LX carbon steel. API 5LX carbon steel coupons were incubated with raw produced water collected from two oil reservoir stations or filter-sterilized produced water. Biofilm 16S rRNA amplicon sequencing revealed that the bacterial community present in the biofilm was dominated by Proteobacteria, including Marinobacter hydrocarbonoclaustics and Marinobacter alkaliphilus.

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Aerobic methane-oxidizing bacteria of the Alphaproteobacteria have been found to express a novel ribosomally synthesized post-translationally modified polypeptide (RiPP) termed methanobactin (MB). The primary function of MB in these microbes appears to be for copper uptake, but MB has been shown to have multiple capabilities, including oxidase, superoxide dismutase and hydrogen peroxide reductase activities, the ability to detoxify mercury species, as well as acting as an antimicrobial agent. Herein, we describe the diversity of known MBs as well as the genetics underlying MB biosynthesis.

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Potential of methane production by co-digestion of food waste with saline sludge produced from sewage receiving seawater toilet flushing was investigated to determine its suitability for food waste management in Hong Kong by making use of excess design capacity of sludge digesters. High salinity of saline sludge (12.8 mS/cm) affected degradation of organic compounds resulting in an increase in sCOD by 135% as compared to an increase by 283% in treatments with non-saline sludge (4.

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Article Synopsis
  • Food waste (FW) is a significant environmental issue that can be turned into a valuable resource through sustainable management and technologies like anaerobic digestion (AD).
  • Conventional AD is not very effective for managing FW alone due to its high levels of organic content and volatile fatty acids, requiring improved methods and inputs for better performance.
  • The article focuses on the benefits of co-digestion of FW with sewage sludge (SS), aiming to enhance biogas production and reviews current strategies and practices in both Hong Kong and globally.
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In present study, the efficiency of three oleaginous yeasts i.e., Yarrowia lipolytica, Rhodotorula glutinis and Cryptococcus curvatus were compared for their lipid assimilation capacities using three different FW-leachates as a medium.

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  • The study focuses on the removal of long-chain hydrocarbons and n-alkanes from oil-contaminated environments using bio-augmentation with efficient microbes.
  • It compares the biodegradation efficiency of pure bacterial isolates and a mixed consortium, finding that the mixed consortium outperforms pure strains in degrading C18 but pure strains excel in degrading C20.
  • Moreover, enzyme activities such as alkane hydroxylase, alcohol dehydrogenase, and lipase were highest in the mixed consortium, highlighting the importance of bacterial hydrophobicity in optimizing hydrocarbon degradation.
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Biotechnological production of vanillin is gaining momentum as the natural synthesis of vanillin that is very expensive. Ferulic acid (FA), a costly compound, is used as the substrate to produce vanillin biotechnologically and the making process is still expensive. Therefore, this study investigated the practical use of an agrobiomass waste, rice bran, and provides the first evidence of a cost-effective production of vanillin within 24 h of incubation using recombinant Pediococcus acidilactici BD16 (fcs /ech ).

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Methane mitigation in landfill top cover soils is mediated by methanotrophs whose optimal methane (CH) oxidation capacity is governed by environmental and complex microbial community interactions. Optimization of CH remediating bio-filters need to take microbial responses into account. Divalent copper (Cu) and iron (Fe) are present in landfills at variable ratios and play a vital role in methane oxidation capacity and growth of methanotrophs.

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Composting of pig manure is a challenging task that requires appropriate co-substrate and bulking agent to provide optimum composting conditions and reduce nitrogen loss. In this study, paper waste is co-composted with pig manure as well as wood chips as the bulking agents. These raw materials were mixed at three different ratios of paper: pig manure: wood chips = 1:1:0 (pile 1), 3:2:1 (pile 2) and 3:1:1(pile 3), respectively.

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Anaerobic co-digestion of food waste with primary sewage sludge is beneficial for urban centers, while the optimized conditions reported in the literature are not locally suitable for Hong Kong. Therefore, the present study was aimed to develop an optimized mixing ratio of food waste to chemically enhanced primary-treated sewer sludge (CEPT) for co-digestion using batch tests under mesophilic (37°C) and thermophilic (55°C) conditions. The mixing ratios of 1:1, 1:2, 1:3, 2:1 and 3:1 (v v(-1)) of food waste to CEPT sludge was tested under the following conditions: temperature - 35°C and 55°C; pH - not regulated; agitation - 150 rpm and time - 20 days.

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Robust methanotrophic consortia for methane (CH) remediation and by-product development are presently not readily available for industrial use. In this study, a mixed methanotrophic consortium (MMC), sequentially enriched from a marine sediment, was assessed for CH removal efficiency and potential biomass-generated by-product development. Suitable packing material for bio-filters to support MMC biofilm establishment and growth was also evaluated.

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