Klaus Riedel

A fast estimation of biochemical oxygen demand using microbial sensors

SummaryMicrobial amperometric sensors for biochemical oxygen demand (BOD) determination using Bacillus subtilis or Trichosporon cutaneum cells immobilized in polyvinylalcohol have been developed. These sensors allow BOD measurements with very short response times (15–30s), a level of precision of ±5% and an operation stability of 30 days. A linear range was obtained for a B. subtilis-based sensor up to 20 mg/l BOD and for a T. cutaneum-based sensor up to 100 mg/l BOD using a glucose/glutamic acid standard.

Amperometric measurement of copper ions with a deputy substrate using a novel Saccharomyces cerevisiae sensor.

The first microbial biosensor to detect Cu2+ by an amperometric method has been developed. For this purpose, recombinant Saccharomyces cerevisiae strains are suitable as the microbial component. These strains contain plasmids with the Cu2+-inducible promoter of the CUP1-gene from Saccharomyces cerevisiae fused to the lacZ-gene from E. coli. On this sensor the CUP1 promoter is first induced by the Cu2+-containing probe and subsequently lactose is used as a deputy substrate to make the measurement. If Cu2+ is present in the sample, these recombinant strains are able to utilize lactose as a carbon source, which leads to alterations in the oxygen consumption of the cells. The sensor measured Cu2+ in a concentration range between 0.5 and 2 mM CuSO4. In addition, an indirect amperometric measurement principle was developed which allows the detection of samples containing Cu2+ and fast biodegradable substances.

Biosensors: Fundamentals, applications and trends☆

Abstract Enzyme electrodes and optical immunosensors are at the leading edge of the biosensor field. The sensitivity of multi-enzyme electrodes is shifted to the subnanomolar concentration range. With monoenzyme sensors, several thousand samples per hour are measurable. Direct as well as enzyme-labelled immunosensors nowadays reach the sensitivity of immunoassays. The effect of non-specific binding is the biggest challenge for further improvement. Using multi-enzyme systems or intact cells, biologically related parameters, e.g., taste, odour, fatigue substances, mutagenicity, allergenicity and biological oxygen demand are quantifiable. Further progress is expected by applying tailor-made enzymes, antibodies and neuronal networks.

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl) sulfonate (PCS) part I: construction and characterization of the microbial sensor

A microbial biosensor based on the yeast Arxula adeninivorans LS3 has been developed for measurement of biodegradable substances. Arxula is immobilized in the hydrogel poly(carbamoyl) sulfonate (PCS). The immobilized yeast membrane is placed in front of an oxygen electrode with -600 mV versus Ag/AgCl. Arxula is salt tolerant; it can give a stable signal up to 2.5 M NaCl in sample (120 mM in measuring cell). The sensors measurements are highly correlated to BOD5 measurements. It has a very high stability which can last for 40 day without any decrease in signal. The linear range of the sensor is up to a corresponding BOD value of 550 mg/l.

Arxula adeninivorans based sensor for the estimation of BOD

Abstract A microbial amperometric sensor for the determination of biochemical oxygen demand (BOD) using the yeast Arxula adeninivorans immobilized in polyvinylalcohol has been developed. The sensor with this microbial species has a wide substrate spectrum and allows BOD measurement with very short response times (70 sec), with an operation stability over 1 month, and a serial coefficient of ±5% when a standard solution containing 275 mg/L BOD was employed. A linear range was obtained up to 550 mg/L BOD using a glucose standard. The BOD-sensor was used to determine the BOD of various waste waters.

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl)sulfonate (PCS) Part II: Application of the novel biosensor to real samples from coastal and island regions

A microbial sensor for rapid measurement of the amount of biodegradable substances based on the salt-tolerant yeast Arxula adeninivorans LS3 has been developed especially for coastal and island regions. Our parameter, the so-called sensorBOD, that is available after only a few minutes, agrees with the 5-day value for the biochemical oxygen demand (BOD5) very well. We have employed the Arxula sensor in the short-time estimation and supervision of the BOD of both domestic and industrial wastewater with high salinity. The novel sensor makes it possible to monitor the different types of wastewater rapidly without pretreatment, and it can be used for an active process control of sewage treatment works. Compared to a commercially available sensor, the novel sensor achieves better agreement between sensorBOD and BOD5 measurements with salt containing samples.

Measurement of biodegradable substances with a mycelia-sensor based on the salt tolerant yeast Arxula adeninivorans LS3

Abstract The microbial sensor based on budding cells of the dimorphic yeast Arxula adeninivorans LS3 is one of the best suitable sensors for rapid measurement of biodegradable substances. However, Arxula is able to change its morphology (budding cells ⇔ mycelia) in response to the cultivation temperature. The suitability of such mycelia was tested as microbial sensor component. The mycelia-based sensor possess a similar linear response, stability, limit of determination and detection compared with the conventional budding cell-based sensor. However, differences exist in the storage capacity and substrate specificity: the mycelia-sensor has with six months a better storage stability as the conventional sensor, achieves a higher sensitivity for specific amino acids or sugars, shows a better correlation between sensorBOD and the BOD 5 -value with yeast extract as model wastewater and is more suitable for measurement of salt water.

Microbial sensors for determination of aromatics and their chloroderivatives. Part II: Determination of chlorinated phenols using a Rhodococcus-containing biosensor

An amperometric biosensor for determination of phenol and chlorophenols using Rhodococcus has been developed. This sensor is more sensitive to phenol and chlorophenols, especially to mono- and dichlorinated phenol, than to benzoate and monochlorobenzoates. The incubation of the sensor with phenol and its chlorinated derivatives enhanced the activity of the microbial sensor for these compounds. A linear relationship between the current range and the concentration of phenol, 2-, 3- and 4-chlorophenol was observed up to 20 μmol/l. The detection limit for all studied substrates was 4 μmol/l. The current difference was reproducible within 5.5% when the test solution contained 40 μmol phenol/l.

A microbial sensor for detecting inhibitors of nitrification in wastewater

A biosensor for rapid and reproducible measurements of inhibitors of nitrification in environmental samples has been developed. The biosensor is mainly designed to be used for wastewater control and consists of a Clark oxygen probe as a transducer and an immobilised mixed nitrifying culture as the microbial component. The measuring principle is based on the direct determination of bacterial metabolic activity by measuring the oxygen consumption rate of the microbial immobilisate. Both the prototype of a laboratory device and a field device have been realised. The laboratory device can be used to determine the nitrification inhibiting effect of individual chemical compounds as well as of environmental samples. The field device was constructed for on-line monitoring of inhibitors in sewage systems.

Microbial sensor for aspartame

SummaryA microbial amperometric sensor using immobilized Bacillus subtilis cells was developed for the determination of the dipeptide sweetener aspartame (l-aspartyl-l-phenylalaninemethylester). From 0.07 to 0.6 mmol/l aspartame, a linear dependence of the initial current change (i.e., change in respiration rate) was obtained. The sensitivity for aspartame was one order of magnitude higher than for its amino acid constituents. The microbial sensor was stable for 8 weeks.