Journal of Industrial Microbiology & Biotechnology, 2001
The effect of microbial enzymes in reducing the disposable solid content of sludge was investigat... more The effect of microbial enzymes in reducing the disposable solid content of sludge was investigated. A mixture of industrial cellulase, protease, and lipase, in equal proportion by weight, reduced total suspended solids (TSS) by 30–50% and improved settling of solids. An increase in solid reduction was observed with increasing enzyme concentration. The effect of combinations of enzyme treatments indicated that two-enzyme combinations of protease and cellulase produced better solid reduction than individual enzymes and that lipase further augmented this effect. Among the individual enzymes, protease produced a more settleable sludge as compared to cellulase and lipase. Adjustment of the pH of the enzymatically treated sludge to the acidic range (pH 2–4) further improved solid reduction, and adjustment to the alkaline range (pH 10–12) improved settleability. Journal of Industrial Microbiology & Biotechnology (2001) 26, 383–386.
... Chemical, Oxidation, Effective decolorization of various kinds of dyes; problems associated w... more ... Chemical, Oxidation, Effective decolorization of various kinds of dyes; problems associated with by ... Biological, Biosorption, Microbial biomass to sorb and remove dyes from wastewater is still in the ... with disposal of the dye-adsorbed biomass; may be regenerated using chemicals. ...
World Journal of Microbiology & Biotechnology, 2001
The combined effects of enzyme, pH and temperature treatments for removal of pathogens from sewag... more The combined effects of enzyme, pH and temperature treatments for removal of pathogens from sewage sludge were investigated. An adjustment to pH 10 for 24-h at 23 °C or a 3-h hold at 50 °C resulted in a 100% kill of coliforms but a significant count of Salmonella species still survived. However, pH adjustment to 12 with a hold of 48-h at 23 °C or pH adjustment to 10 or 12 and a 3-h hold at 60 °C was required to achieve a 100% kill of Salmonella species. Although protease enzyme treatment at 40 °C with or without alkali treatment eliminated coliforms completely, Salmonella counts were reduced by two to three orders of magnitude. However, complete elimination of pathogens was observed when enzymatic treatment was provided at 50 °C. Application of alkaline protease, through its combined beneficial effects in pathogen reduction, solids reduction and improved solids settling, has potential as an effective procedure for processing of sewage sludge.
World Journal of Microbiology & Biotechnology, 2004
Nitroaromatic compounds constitute a major class of widely distributed environmental contaminants... more Nitroaromatic compounds constitute a major class of widely distributed environmental contaminants. Compounds like nitrobenzene, nitrotoluenes, nitrophenols, nitrobenzoates and nitrate esters are of considerable industrial importance. They are frequently used as pesticides, explosives, dyes, and in the manufacture of polymers and pharmaceuticals. Many nitroaromatic compounds and their conversion products have been shown to have toxic or mutagenic properties. Most of them are biodegradable in nature by various microorganisms. However, most contaminated environments have combinations of nitroaromatic compounds present, which complicates the bioremediation efforts. During the last 10 years, research on the biodegradation of nitroaromatic compounds has yielded a wealth of information on the microbiological, biochemical and genetic aspects of the process. New metabolic pathways have been discovered and genes and enzymes responsible for key transformation reactions have been identified and characterized. Knowledge and advances in pathway engineering have helped further understanding of the nature of nitroaromatic biodegradation and the development of bioremediation solutions. In this paper, an overview of recent developments on the biodegradation of nitrogen-containing xenobiotics is presented.
Journal of Industrial Microbiology & Biotechnology, 1998
The physiological roles of omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid ha... more The physiological roles of omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid have been investigated in detail and microbial strains producing these polyunsaturated fatty acids have been characterised. It has recently been suggested that docosapentaenoic acid may have an important role, especially in infant nutrition, and that its positive health effects have been overlooked. Docosapentaenoic acid (C22:5, ω-3) production by a strain of Pythium acanthicum ATCC 18660 was thus investigated. Optimum conditions for growth of P. acanthicum ATCC 18660 and docosapentaenoic acid production were: pH 6.0, temperature 20°C and incubation time, 10 days. Among different saccharides and complex nitrogen sources tested, glucose and sodium glutamate were preferred carbon and nitrogen sources, respectively. Maximum biomass content (10.4 g L−1) and docosapentaenoic acid yield (49.9 mg L−1) were obtained in 10 days. An increase in docosapentaenoic acid volumetric yields to 108–110 mg L−1 was obtained when linseed oil was used to supplement glucose or soy flour-containing medium. Batch feeding of additional glucose or linseed oil further enhanced the docosapentaenoic acid volumetric yield to 132 mg L−1 and 125 mg L−1, respectively, in 14 days. The specific production of docosapentaenoic acid in preliminary experiments ranged from 1.0–5.0 mg g−1 biomass. As conditions were optimised, docosapentaenoic acid specific production titers were generally in the range of 4.0–5.5 mg g−1 and increases in docosapentaenoic acid volumetric production could be attributed to increased biomass production. The limited improvement obtained by modifying culture conditions indicates that increasing volumetric yields of docosapentaenoic acid by modifying culture conditions appears to represent a significant barrier to commercialisation of such a process and suggests a more fundamental manipulation of metabolism and physiology is required.
World Journal of Microbiology & Biotechnology, 2002
Biological treatment of a dimethyl phthalate (DMP)-containing waste stream was evaluated in packe... more Biological treatment of a dimethyl phthalate (DMP)-containing waste stream was evaluated in packed-bed bioreactors using an acclimated mixed bacterial culture. The passive immobilization start-up strategy was successful in the development of a stable biofilm on the packing material in the reactor. Nutrient supplementation significantly improved the removal efficiency. High removal rates with 100% efficiencies of DMP removal were achieved up to the phthalate-loading rate of 560 g/m3 h.
Journal of Industrial Microbiology & Biotechnology, 2001
The effect of microbial enzymes in reducing the disposable solid content of sludge was investigat... more The effect of microbial enzymes in reducing the disposable solid content of sludge was investigated. A mixture of industrial cellulase, protease, and lipase, in equal proportion by weight, reduced total suspended solids (TSS) by 30–50% and improved settling of solids. An increase in solid reduction was observed with increasing enzyme concentration. The effect of combinations of enzyme treatments indicated that two-enzyme combinations of protease and cellulase produced better solid reduction than individual enzymes and that lipase further augmented this effect. Among the individual enzymes, protease produced a more settleable sludge as compared to cellulase and lipase. Adjustment of the pH of the enzymatically treated sludge to the acidic range (pH 2–4) further improved solid reduction, and adjustment to the alkaline range (pH 10–12) improved settleability. Journal of Industrial Microbiology & Biotechnology (2001) 26, 383–386.
... Chemical, Oxidation, Effective decolorization of various kinds of dyes; problems associated w... more ... Chemical, Oxidation, Effective decolorization of various kinds of dyes; problems associated with by ... Biological, Biosorption, Microbial biomass to sorb and remove dyes from wastewater is still in the ... with disposal of the dye-adsorbed biomass; may be regenerated using chemicals. ...
World Journal of Microbiology & Biotechnology, 2001
The combined effects of enzyme, pH and temperature treatments for removal of pathogens from sewag... more The combined effects of enzyme, pH and temperature treatments for removal of pathogens from sewage sludge were investigated. An adjustment to pH 10 for 24-h at 23 °C or a 3-h hold at 50 °C resulted in a 100% kill of coliforms but a significant count of Salmonella species still survived. However, pH adjustment to 12 with a hold of 48-h at 23 °C or pH adjustment to 10 or 12 and a 3-h hold at 60 °C was required to achieve a 100% kill of Salmonella species. Although protease enzyme treatment at 40 °C with or without alkali treatment eliminated coliforms completely, Salmonella counts were reduced by two to three orders of magnitude. However, complete elimination of pathogens was observed when enzymatic treatment was provided at 50 °C. Application of alkaline protease, through its combined beneficial effects in pathogen reduction, solids reduction and improved solids settling, has potential as an effective procedure for processing of sewage sludge.
World Journal of Microbiology & Biotechnology, 2004
Nitroaromatic compounds constitute a major class of widely distributed environmental contaminants... more Nitroaromatic compounds constitute a major class of widely distributed environmental contaminants. Compounds like nitrobenzene, nitrotoluenes, nitrophenols, nitrobenzoates and nitrate esters are of considerable industrial importance. They are frequently used as pesticides, explosives, dyes, and in the manufacture of polymers and pharmaceuticals. Many nitroaromatic compounds and their conversion products have been shown to have toxic or mutagenic properties. Most of them are biodegradable in nature by various microorganisms. However, most contaminated environments have combinations of nitroaromatic compounds present, which complicates the bioremediation efforts. During the last 10 years, research on the biodegradation of nitroaromatic compounds has yielded a wealth of information on the microbiological, biochemical and genetic aspects of the process. New metabolic pathways have been discovered and genes and enzymes responsible for key transformation reactions have been identified and characterized. Knowledge and advances in pathway engineering have helped further understanding of the nature of nitroaromatic biodegradation and the development of bioremediation solutions. In this paper, an overview of recent developments on the biodegradation of nitrogen-containing xenobiotics is presented.
Journal of Industrial Microbiology & Biotechnology, 1998
The physiological roles of omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid ha... more The physiological roles of omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid have been investigated in detail and microbial strains producing these polyunsaturated fatty acids have been characterised. It has recently been suggested that docosapentaenoic acid may have an important role, especially in infant nutrition, and that its positive health effects have been overlooked. Docosapentaenoic acid (C22:5, ω-3) production by a strain of Pythium acanthicum ATCC 18660 was thus investigated. Optimum conditions for growth of P. acanthicum ATCC 18660 and docosapentaenoic acid production were: pH 6.0, temperature 20°C and incubation time, 10 days. Among different saccharides and complex nitrogen sources tested, glucose and sodium glutamate were preferred carbon and nitrogen sources, respectively. Maximum biomass content (10.4 g L−1) and docosapentaenoic acid yield (49.9 mg L−1) were obtained in 10 days. An increase in docosapentaenoic acid volumetric yields to 108–110 mg L−1 was obtained when linseed oil was used to supplement glucose or soy flour-containing medium. Batch feeding of additional glucose or linseed oil further enhanced the docosapentaenoic acid volumetric yield to 132 mg L−1 and 125 mg L−1, respectively, in 14 days. The specific production of docosapentaenoic acid in preliminary experiments ranged from 1.0–5.0 mg g−1 biomass. As conditions were optimised, docosapentaenoic acid specific production titers were generally in the range of 4.0–5.5 mg g−1 and increases in docosapentaenoic acid volumetric production could be attributed to increased biomass production. The limited improvement obtained by modifying culture conditions indicates that increasing volumetric yields of docosapentaenoic acid by modifying culture conditions appears to represent a significant barrier to commercialisation of such a process and suggests a more fundamental manipulation of metabolism and physiology is required.
World Journal of Microbiology & Biotechnology, 2002
Biological treatment of a dimethyl phthalate (DMP)-containing waste stream was evaluated in packe... more Biological treatment of a dimethyl phthalate (DMP)-containing waste stream was evaluated in packed-bed bioreactors using an acclimated mixed bacterial culture. The passive immobilization start-up strategy was successful in the development of a stable biofilm on the packing material in the reactor. Nutrient supplementation significantly improved the removal efficiency. High removal rates with 100% efficiencies of DMP removal were achieved up to the phthalate-loading rate of 560 g/m3 h.
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Papers by Ajay Owen