scholarly journals Microbes in deionized water: Implications for maintenance of laboratory water production system

2013 ◽  
Author(s):  
Wenfa Ng
Keyword(s):  
Ion Exchange ◽  
Microbial Diversity ◽  
Production System ◽  
Cell Concentration ◽  
Tap Water ◽  
Viable Cell ◽  
Just In Time ◽  
Water Production ◽  
Viable Cell Concentration ◽  
Salt Solutions

Microbes, with their diverse metabolic capabilities and great adaptability, occupy almost every conceivable ecological niche on Earth – thus, could they survive in the oligotrophic (i.e., nutrient-poor) deionized (DI) water that we use for our experiments? Observations of white cauliflower-like lumps and black specks in salt solutions after months of storage in plastic bottles prompted the inquisition concerning the origin and nature of the “contaminants.” Hypothesising that the “contaminants” may be microbes from DI water, a series of growth experiments was conducted to detect and profile the microbial diversity in fresh DI water - produced on a just-in-time basis by a filter-cum-ion-exchange system with tap water as feed. While microbes could also be present on the surfaces and headspace of the unsterilized polyethylene bottles, investigating whether microbes are present in freshly produced DI water provides a more stringent performance test of the production system. Inoculation of DI water on R2A agar followed by multi-day aerobic cultivation revealed the presence of a wide variety of microbes (total viable cell concentration of ~103 colony forming units (CFU) per mL) with differing pigmentations, growth rates as well as colony sizes and morphologies. Additionally, greater abundance and diversity of microbes was recovered at 30 oC relative to 25 and 37 oC; most probably due to adaptation of microbes to tropical ambient water temperatures of 25 to 30 oC. Comparative experiments with tap water as inoculum recovered a significantly smaller number and diversity of microbes; thereby, suggesting that monochloramine residual disinfectant in tap water was effective in inhibiting cell viability. In contrast, possible removal of monochloramine by adsorption onto ion-exchange resins – and thus, alleviation of a source of environmental stress - might explain the observed greater diversity and abundance of viable microbes in DI water. Collectively, this study confirmed the presence of microbes in fresh DI water – and suggested a possible source for the “contaminants” in prepared salt solutions. Propensity of microbes for forming biofilm on various surfaces suggested that intermittent flow in just-in-time DI water production provided opportunities for cell attachment and biofilm formation in the system during water stagnation, and subsequent dislodgement and resuspension of cells upon water flow. Thus, regular maintenance and cleaning of the production system should help reduce DI water’s microbial load. Additionally, simple and low-cost culture experiments on agar medium can provide a qualitative and semi-quantitative estimate of microbial diversity and viable cell concentration in DI water, respectively; which, along with regular monitoring of water resistivity or conductivity, comprise a trio of tests useful for detecting possible contamination or, deterioration of DI water’s chemical and microbiological quality.

scholarly journals Microbes in deionized water: Implications for maintenance of laboratory water production system

2016 ◽  
Author(s):  
Wenfa Ng ◽  
Yen-Peng Ting
Keyword(s):  
Ion Exchange ◽  
Microbial Diversity ◽  
Production System ◽  
Cell Concentration ◽  
Tap Water ◽  
Viable Cell ◽  
Just In Time ◽  
Water Production ◽  
Viable Cell Concentration ◽  
Salt Solutions

Microbes, with their diverse metabolic capabilities and great adaptability, occupy almost every conceivable ecological niche on Earth – thus, could they survive in the oligotrophic (i.e., nutrient-poor) deionized (DI) water that we use for our experiments? Observations of white cauliflower-like lumps and black specks in salt solutions after months of storage in plastic bottles prompted the inquisition concerning the origin and nature of the “contaminants”. Hypothesizing that the “contaminants” may be microbes from DI water, a series of growth experiments was conducted to detect and profile the microbial diversity in fresh DI water - produced on a just-in-time basis by a filter-cum-ion-exchange system with tap water as feed. While microbes could also be present on the surfaces and headspace of the unsterilized polyethylene bottles, investigating whether microbes are present in freshly produced DI water provides a more stringent performance test of the production system. Inoculation of DI water on R2A agar followed by multi-day aerobic cultivation revealed the presence of a wide variety of microbes (total viable cell concentration of ~103 colony forming units (CFU) per mL) with differing pigmentations, growth rates as well as colony sizes and morphologies. Additionally, greater abundance and diversity of microbes was recovered at 30 oC relative to 25 and 37 oC; most probably due to adaptation of microbes to tropical ambient water temperatures of 25 to 30 oC. Comparative experiments with tap water as inoculum recovered a significantly smaller number and diversity of microbes; thereby, suggesting that monochloramine residual disinfectant in tap water was effective in inhibiting cell viability. In contrast, possible removal of monochloramine by adsorption onto ion-exchange resins – and thus, alleviation of a source of environmental stress - might explain the observed greater diversity and abundance of viable microbes in DI water. Collectively, this study confirmed the presence of microbes in fresh DI water – and suggested a possible source of the “contaminants” in prepared salt solutions. Propensity of microbes for forming biofilm on various surfaces suggested that intermittent flow in just-in-time DI water production provided opportunities for cell attachment and biofilm formation in the system during water stagnation, and subsequent dislodgement and resuspension of cells upon water flow. Thus, regular maintenance and cleaning of the production system should help reduce DI water’s microbial load. Additionally, simple and low-cost culture experiments on agar medium can provide a qualitative and semi-quantitative estimate of microbial diversity and viable cell concentration in DI water, respectively, and along with regular monitoring of water resistivity or conductivity, comprise a trio of tests useful for detecting possible contamination, or deterioration of DI water’s chemical and microbiological quality.

scholarly journals Microbes in deionized water: Implications for maintenance of laboratory water production system

2015 ◽  
Author(s):  
Wenfa Ng ◽  
Yen-Peng Ting
Keyword(s):  
Ion Exchange ◽  
Microbial Diversity ◽  
Production System ◽  
Cell Concentration ◽  
Tap Water ◽  
Viable Cell ◽  
Just In Time ◽  
Water Production ◽  
Viable Cell Concentration ◽  
Salt Solutions

Microbes, with their diverse metabolic capabilities and great adaptability, occupy almost every conceivable ecological niche on Earth – thus, could they survive in the oligotrophic (i.e., nutrient-poor) deionized (DI) water that we use for our experiments? Observations of white cauliflower-like lumps and black specks in salt solutions after months of storage in plastic bottles prompted the inquisition concerning the origin and nature of the “contaminants.” Hypothesising that the “contaminants” may be microbes from DI water, a series of growth experiments was conducted to detect and profile the microbial diversity in fresh DI water - produced on a just-in-time basis by a filter-cum-ion-exchange system with tap water as feed. While microbes could also be present on the surfaces and headspace of the unsterilized polyethylene bottles, investigating whether microbes are present in freshly produced DI water provides a more stringent performance test of the production system. Inoculation of DI water on R2A agar followed by multi-day aerobic cultivation revealed the presence of a wide variety of microbes (total viable cell concentration of ~103 colony forming units (CFU) per mL) with differing pigmentations, growth rates as well as colony sizes and morphologies. Additionally, greater abundance and diversity of microbes was recovered at 30 oC relative to 25 and 37 oC; most probably due to adaptation of microbes to tropical ambient water temperatures of 25 to 30 oC. Comparative experiments with tap water as inoculum recovered a significantly smaller number and diversity of microbes; thereby, suggesting that monochloramine residual disinfectant in tap water was effective in inhibiting cell viability. In contrast, possible removal of monochloramine by adsorption onto ion-exchange resins – and thus, alleviation of a source of environmental stress - might explain the observed greater diversity and abundance of viable microbes in DI water. Collectively, this study confirmed the presence of microbes in fresh DI water – and suggested a possible source for the “contaminants” in prepared salt solutions. Propensity of microbes for forming biofilm on various surfaces suggested that intermittent flow in just-in-time DI water production provided opportunities for cell attachment and biofilm formation in the system during water stagnation, and subsequent dislodgement and resuspension of cells upon water flow. Thus, regular maintenance and cleaning of the production system should help reduce DI water’s microbial load. Additionally, simple and low-cost culture experiments on agar medium can provide a qualitative and semi-quantitative estimate of microbial diversity and viable cell concentration in DI water, respectively; which, along with regular monitoring of water resistivity or conductivity, comprise a trio of tests useful for detecting possible contamination or, deterioration of DI water’s chemical and microbiological quality.

scholarly journals Microbes in deionized water: Implications for maintenance of laboratory water production system

2017 ◽  
Author(s):  
Wenfa Ng
Keyword(s):  
Ion Exchange ◽  
Production System ◽  
Cell Concentration ◽  
Tap Water ◽  
Viable Cell ◽  
Intermittent Flow ◽  
Just In Time ◽  
Water Production ◽  
Viable Cell Concentration ◽  
Salt Solutions

Microbes, with their vast metabolic capabilities and great adaptability, occupy almost every conceivable ecological niche on Earth. Thus, could they survive in the oligotrophic (i.e., nutrient poor) deionized (DI) water that we use for experiments? Observations of white cauliflower-like lumps and black specks in salt solutions after months of storage in plastic bottles prompted the inquisition concerning the origin and nature of the “contaminants”. Hypothesizing that the “contaminants” may be microbes from DI water, a series of growth experiments was conducted to detect and profile the diversity of microbes in fresh DI water, produced on a just-in-time basis by a filter cum ion exchange system with tap water as feed. While microbes could also be present on the surfaces and headspace of the unsterilized polyethylene bottles, investigating whether microbes are present in freshly produced DI water provides a more stringent performance test of the production system. Inoculation of DI water on R2A agar followed by multi-day aerobic cultivation revealed the presence of a wide variety of microbes (total viable cell concentration of ~103 colony forming units (CFU) per mL) with differing pigmentations, growth rates, as well as colony sizes and morphologies. Additionally, greater abundance and diversity of microorganisms was recovered at 30 oC compared to 25 and 37 oC; most probably due to adaptation of microbes to tropical ambient water temperatures of 25 to 30 oC. Comparative experiments with tap water as inoculum recovered a significantly smaller number and diversity of microorganisms; thus, suggesting that monochloramine residual disinfectant in tap water was effective in inhibiting cell viability. In contrast, possible removal of monochloramine by adsorption onto ion exchange resins (and thus, alleviation of a source of environmental stress) might explain the observed greater diversity and abundance of viable microbes in DI water. Collectively, this study confirmed the presence of microbes in fresh DI water, and suggested a possible source of the “contaminants” in prepared salt solutions. Propensity of microbes in forming biofilm on various surfaces suggested that intermittent flow in just-in-time DI water production provided opportunities for cell attachment and biofilm formation during water stagnation, and subsequent dislodgement and resuspension of cells upon water flow. Thus, regular maintenance and cleaning of the production system should help reduce DI water’s microorganism load. In addition, simple and low cost culture experiments on solid medium can provide a qualitative and semi-quantitative estimate of microbial diversity and viable cell concentration in DI water, respectively. The above, together with regular monitoring of water resistivity or conductivity, comprise a trio of tests useful for detecting possible contamination, or deterioration of DI water’s chemical and microbiological quality.

scholarly journals Microbes in deionized water: Implications for maintenance of laboratory water production system

2016 ◽  
Author(s):  
Wenfa Ng ◽  
Yen-Peng Ting
Keyword(s):  
Ion Exchange ◽  
Production System ◽  
Cell Concentration ◽  
Tap Water ◽  
Viable Cell ◽  
Intermittent Flow ◽  
Just In Time ◽  
Water Production ◽  
Viable Cell Concentration ◽  
Salt Solutions

Microbes, with their vast metabolic capabilities and great adaptability, occupy almost every conceivable ecological niche on Earth – thus, could they survive in the oligotrophic (i.e., nutrient poor) deionized (DI) water that we use for experiments? Observations of white cauliflower-like lumps and black specks in salt solutions after months of storage in plastic bottles prompted the inquisition concerning the origin and nature of the “contaminants”. Hypothesizing that the “contaminants” may be microbes from DI water, a series of growth experiments was conducted to detect and profile the diversity of microbes in fresh DI water - produced on a just-in-time basis by a filter cum ion exchange system with tap water as feed. While microbes could also be present on the surfaces and headspace of the unsterilized polyethylene bottles, investigating whether microbes are present in freshly produced DI water provides a more stringent performance test of the production system. Inoculation of DI water on R2A agar followed by multi-day aerobic cultivation revealed the presence of a wide variety of microbes (total viable cell concentration of ~103 colony forming units (CFU) per mL) with differing pigmentations, growth rates as well as colony sizes and morphologies. In addition, greater abundance and diversity of microorganisms was recovered at 30 oC compared to 25 and 37 oC; most probably due to adaptation of microbes to tropical ambient water temperatures of 25 to 30 oC. Comparative experiments with tap water as inoculum recovered a significantly smaller number and diversity of microorganisms; thus, suggesting that monochloramine residual disinfectant in tap water was effective in inhibiting cell viability. In contrast, possible removal of monochloramine by adsorption onto ion exchange resins – and thus, alleviation of a source of environment stress - might explain the observed greater diversity and abundance of viable microbes in DI water. Collectively, this study confirmed the presence of microbes in fresh DI water – and suggested a possible source of the “contaminants” in prepared salt solutions. Propensity of microbes in forming biofilm on various surfaces suggested that intermittent flow in just-in-time DI water production provided opportunities for cell attachment and biofilm formation during water stagnation, and subsequent dislodgement and resuspension of cells upon water flow. Thus, regular maintenance and cleaning of the production system should help reduce DI water’s microorganism load. In addition, simple and low cost culture experiments on solid medium can provide a qualitative and semi-quantitative estimate of microbe diversity and viable cell concentration in DI water, respectively. The above, together with regular monitoring of water resistivity or conductivity, comprise a trio of tests useful for detecting possible contamination, or deterioration of DI water’s chemical and microbiological quality.

scholarly journals Microbes in deionized and tap water: Implications for maintenance of laboratory water production system

2018 ◽  
Author(s):  
Wenfa Ng
Keyword(s):  
Ion Exchange ◽  
Production System ◽  
Cell Attachment ◽  
Tap Water ◽  
Keystone Species ◽  
Signaling Molecules ◽  
Intermittent Flow ◽  
Just In Time ◽  
Water Production ◽  
Chelating Compounds

Microbes, with their vast metabolic capabilities and great adaptability, occupy almost every conceivable ecological niche on Earth. Thus, could they survive in oligotrophic deionized (DI) water? Observations of white cauliflower-like lumps and black specks in salt solutions after months of storage in plastic bottles suggested a microbial origin for the “contaminants”. Growth experiments was conducted to profile the microbial diversity of fresh DI water, produced on a just-in-time basis by a filter cum ion exchange system with tap water as feed. Inoculation of DI water on R2A agar and a formulated colourless agar followed by multi-day aerobic incubation revealed the presence of a large variety of microbes with differing pigmentations, growth rates, colony sizes and morphologies. Additionally, greater abundance and diversity of microorganisms was recovered at 30 oC compared to 25 and 37 oC; most probably due to adaptation of microbes to tropical ambient water temperatures of 25 to 30 oC. Comparative experiments with tap water as inoculum recovered a significantly smaller number and diversity of microorganisms; thus, suggesting that monochloramine residual disinfectant in tap water was effective in inhibiting cell viability. In contrast, possible removal of monochloramine by adsorption onto ion exchange resins of the DI water production system might explain the observed greater diversity and abundance of viable microbes in DI water. More importantly, greater diversity and abundance of microbes from tap water were recovered on R2A agar compared to formulated colourless agar, which suggested that chelating compounds in R2A agar could have complexed monochloramine and reduced its toxicity towards microbes. Similar chelating compounds were unlikely to be present in the formulated colourless agar. Finally, keystone species secreting signaling molecules and metabolites could induce the growth of neighbouring cells embedded in the agar matrix. This explained the presence of large clear zones devoid of colonies where there was no keystone species. Additionally, close proximity of colonies on agar suggested that cooperative and neutral relationships guided by exchange of metabolite and signaling molecules might be more prevalent compared to antagonistic relationships in which inhibitory compounds were used. Collectively, this study confirmed the presence of microbes in fresh DI water and tap water. Propensity of microbes in forming biofilm on various surfaces suggested that intermittent flow in just-in-time DI water production provided opportunities for cell attachment and biofilm formation during water stagnation, and subsequent dislodgement and resuspension of cells upon water flow. Thus, regular maintenance and cleaning of the production system should help reduce DI water’s microorganism load.

scholarly journals Microbes in deionized and tap water: Implications for maintenance of laboratory water production system

2018 ◽  
Author(s):  
Wenfa Ng
Keyword(s):  
Ion Exchange ◽  
Production System ◽  
Cell Attachment ◽  
Tap Water ◽  
Keystone Species ◽  
Signaling Molecules ◽  
Intermittent Flow ◽  
Just In Time ◽  
Water Production ◽  
Chelating Compounds

Microbes, with their vast metabolic capabilities and great adaptability, occupy almost every conceivable ecological niche on Earth. Thus, could they survive in oligotrophic deionized (DI) water? Observations of white cauliflower-like lumps and black specks in salt solutions after months of storage in plastic bottles suggested a microbial origin for the “contaminants”. Growth experiments was conducted to profile the microbial diversity of fresh DI water, produced on a just-in-time basis by a filter cum ion exchange system with tap water as feed. Inoculation of DI water on R2A agar and a formulated colourless agar followed by multi-day aerobic incubation revealed the presence of a large variety of microbes with differing pigmentations, growth rates, colony sizes and morphologies. Additionally, greater abundance and diversity of microorganisms was recovered at 30 oC compared to 25 and 37 oC; most probably due to adaptation of microbes to tropical ambient water temperatures of 25 to 30 oC. Comparative experiments with tap water as inoculum recovered a significantly smaller number and diversity of microorganisms; thus, suggesting that monochloramine residual disinfectant in tap water was effective in inhibiting cell viability. In contrast, possible removal of monochloramine by adsorption onto ion exchange resins of the DI water production system might explain the observed greater diversity and abundance of viable microbes in DI water. More importantly, greater diversity and abundance of microbes from tap water were recovered on R2A agar compared to formulated colourless agar, which suggested that chelating compounds in R2A agar could have complexed monochloramine and reduced its toxicity towards microbes. Similar chelating compounds were unlikely to be present in the formulated colourless agar. Finally, keystone species secreting signaling molecules and metabolites could induce the growth of neighbouring cells embedded in the agar matrix. This explained the presence of large clear zones devoid of colonies where there was no keystone species. Additionally, close proximity of colonies on agar suggested that cooperative and neutral relationships guided by exchange of metabolite and signaling molecules might be more prevalent compared to antagonistic relationships in which inhibitory compounds were used. Collectively, this study confirmed the presence of microbes in fresh DI water and tap water. Propensity of microbes in forming biofilm on various surfaces suggested that intermittent flow in just-in-time DI water production provided opportunities for cell attachment and biofilm formation during water stagnation, and subsequent dislodgement and resuspension of cells upon water flow. Thus, regular maintenance and cleaning of the production system should help reduce DI water’s microorganism load.

Response to phage infection of immobilized lactococci during continuous acidification and inoculation of skim milk

1994 ◽  
Vol 61 (4) ◽  
pp. 537-544 ◽  
Author(s):  
Flavia M. L. Passos ◽  
Todd R. Klaenhammer ◽  
Harold E. Swaisgood
Keyword(s):  
Steady State ◽  
Cell Concentration ◽  
Skim Milk ◽  
Viable Cell ◽  
Free Cell ◽  
Viable Cell Concentration ◽  
Immobilized Cell ◽  
Stainless Steel Mesh ◽  
Immobilized Cell Bioreactor ◽  
Column Bioreactor

SummaryA laboratory scale bioreactor was used for continuous acidification and inoculation of milk with a proteinase-negative, lactose-fermenting strain,Lactococcus lactissubsp.lactisC2S. Calcium alginate-entrapped cells were immobilized on a spiral stainless steel mesh incorporated into a column bioreactor and used to acidify and inoculate reconstituted skim milk. Characteristics of the immobilized cell bioreactor (ICB) were compared with those of a free cell bioreactor (FCB) during challenge with a virulent phage. Steady state biomass and lactate productivities were respectively 25-fold and 12-fold larger with the ICB than with the FCB. The ICB and the FCB were inoculated with the prolate phage c2 at multiplicities of infection of 0·25 and 0·02 respectively. Within 90 min of the infection, the FCB viable cell concentration dropped by five orders of magnitude and never recovered, while the plaque forming units/ml increased dramatically. In the ICB, released cells decreased immediately after infection, but subsequently increased, while the plaque forming units/ml steadily declined, indicating that phage were being washed out of the bioreactor. Productivity of FCB decreased to zero, whereas productivity of the ICB only decreased ∼ 60% and subsequently recovered to its initial steady state value.

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