Biosensors for process monitoring

Summary A short review about the biosensor research activities for bioprocess monitoring in the F.R.G. after its reunification is given. The principles of biosensor applications are presented. In situ sensors and sensors based on the principles of flow injection analysis are studied. Some applications of a four-channel enzyme thermistor, bio-field effect transistors, and immunoanalysis systems for real process monitoring are presented.     

Monitoring and control of biotechnological production processes by Bio-FET-FIA-sensors

Summary Single and multisensor field effect transistors (FET) with a pH-sensitive Si/SiO₂/Si₃N₄/Ta₂O₅-gate and reference electrode (for single sensor) were developed and used for manufacturing the following biological (Bio)-FETs: for glucose analysis, glucose oxidase-FET (GOD-FET); for urea analysis, urease-FET; and for cephalosporin C analysis, cephalosporinase-FET. The GOD-FETs were integrated into flow injection analysis (FIA) of the Eppendorf variables analyser (EVA) system and used for monitoring the glucose concentration in microbial cultivation and production processes with recombinant Escherichia coli K12 MF, recombinant E. coli JM103, Saccharomyces cerevisiae H620, and Candida boidinii. Urease-FET-FIA was used to monitor the urea concentration in a simulated cultivation of Cephalosporium acremonium and urease-FET-FIA and GOD-FET-FIA for the monitoring of urea and glucose concentrations in simulated S. cerevisiae cultivations.     

Xylem and Phloem Import of Na+, K+, Rb+, Cs+ and Sb(SO4)2- in Tomato Fruits: Differential Contributions from Stem and Leaf

Wolterbeek, H. Th. and De Bruin, M. 1986. Xylem and phloem importof Na⁺, K⁺ , Rb⁺, Cs⁺ and in tomato fruits: differential contributions from stem and leaf.—J.exp. Bot. 37: 928–939. The transport of Na⁺, K⁺, Rb⁺, Cs⁺ and into developing fruits of tomato (an inbred lineof Lycopersicon esculentum Mill. cv. Tiny Tim) was measured.Element solutions were introduced into the transpiration streamthrough the cut stem bases of plant parts consisting of a stempart with single green fruit, both with and without attachedfully expanded leaf. Measurements were carried out of the accumulationin the fruit of the gamma-ray emitting radiotracers ²⁴Na⁺, ⁴²K⁺,⁸⁶Rb⁺, ¹³⁴Cs⁺ and The transport into the fruit was expressed by a single parameter taking intoaccount volume flows varying with time and experiments. Xylemto phloem transfer in the stem as a source of fruit elementsupply was shown to be inversely related with the velocity offlow of the stem xylem. The results also indicated that thetransfer system in the stem was more rapidly equilibrated thanit was in the leaf. Stem loading of the phloem is suggested as a possible mechanismregulating the solute influx in fruits under varying flow velocitiesof the stem xylem, while fruit influx of phloem solutes, whichwere loaded in the leaf, may play a major role in influx regulationunder conditions of varying solute concentrations. Key words: Alkali ions, tomato fruits, stem and leaf phloem loading     

Changes in Abscisic Acid Content in Axis and Cotyledons of Developing Phaseolus vulgaris Embryos and their Physiological Consequences

Prevost, I. and Le Page–Degivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.—J.exp. Bot. 36: 1900–1905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radio–immunoassay.During embryogenesis, a similar pattern was observed in bothtissues: ABA increased to a maximum 29 d after an thesis, followedby a decrease as the seed matured. The level of ABA in the cotyledonswas always much higher than that in the axes. In in vitro cultures,the duration of the lag phase before germination of isolatedembryonic axes increased with ABA content. The presence of cotyledonsalways lengthened the lag phase; longer lag phases were associatedwith greater concentrations of ABA in the cotyledons. Moreoverthe presence of cotyledons stimulated the growth of seedlings. Key words: ABA distribution, embryo maturation, axis and embryo germinability     

Degradation of halogenated aliphatic compounds by Xanthobacter autotrophicus GJ10

A bacterium that is able to utilize a number of halogenated short-chain hydrocarbons and halogenated carboxylic acids as sole carbon source for growth was identified as a strain of Xanthobacter autotrophicus. The organism constitutively produces two different dehalogenases. One enzyme is specific for halogenated alkanes, whereas the other, which is more heat stable and has a higher pH optimum, is specific for halogenated carboxylic acids. Haloalkanes were hydrolyzed in cell extracts to produce alcohols and halide ions, and a route for the metabolism of 1,2-dichlorethane is proposed. Both dehalogenases show a broad substrate specificity, allowing the degradation of bromine- and chlorine-substituted organic compounds. The results show that X. autotrophicus may play a role in the degradation of organochlorine compounds and that hydrolytic dehalogenases may be involved in the microbial metabolism of short-chain halogenated hydrocarbons in microorganisms.     

Penicillin acylase production by E. coli

Enzyme production with E. coli ATCC 11105, in a complex medium using phenylacetic acid as inducer is carried out in a stirred-tank reactor of 10 dm³ and an airlift tower-loop reactor of 60 dm³ with outer loop at a temperature of 27 °C. The optimum inducer concentration was 0.8 kg/m³, which was kept constant by fed-batch operation. The optimum of the relative dissolved O₂-concentration with regard to saturation is below 10% in a stirred-tank reactor and at 35% in a tower-loop reactor. It was kept constant by parameter-adaptive control of the aeration rate. In a stirred-tank enzyme productivity is slightly higher than in a tower-loop reactor, and much higher than in a bubble column reactor.List of Symbols CPR kg/(m³ h) CO₂-production rate - OTR kg/(m³ h) O₂-transfer rate - OUR kg/(m³ h) O₂-utilization rate - PAA phenylacetic acid (inducer) - RQ = CPR/OUR respiratory quotient - X kg/m³ cell mass concentration - _m h^–1 maximum specific growth rate     

Growth of E. coli in a stirred tank and in an air lift tower reactor with an outer loop

E. coli ATCC 11105 was cultivated in a 10-1 stirred tank reactor and in a 60-1 tower loop reactor in batch and continuous operation. By on-line measurements of O₂ and CO₂ concentrations in the outlet gas, pH, temperature, cell mass concentration X as well as dissolved O₂ concentration along the tower in the broth, gas holdup, broth recirculation rate through the loop and by offline measurements of substrate concentration DOC and cell mass concentration along the tower, the maximum specific growth rate _m , yield coefficients Y _X/S. Y _X/DOC and were evaluated in stirred tank and tower loop in batch and continuous cultures with and without motionless mixers in the tower and at different broth circulation rates through the loop. To control the accuracy of the measurements the C balance was calculated and 95% of the C content was covered.The biological parameters determined depend on the mode of operation as well as on the reactor used. Furthermore, they depend on the recirculation rate of the broth and built-ins in the tower. The unstructured cell and reactor models are unable to explain these differences. Obviously, structured cell and reactor models are needed. The cell mass concentration can be determined on line by NADH fluorescence in balanced growth, if the model parameters are determined under the same operational conditions in the same reactor.List of Symbols a, b empirical parameters in Eq. (1) - CPR kg/(m³ h) CO₂ production rate - C kg/m³ concentration - D l/h dilution rate - DOC kg/m³ dissolved organic carbon - I net. fluorescence intensity - K _S kg/m³ Monod constant - k _L a l/h volumetric mass transfer coefficient - OTR kg/(m³ h) oxygen transfer rate - OUR kg/(m³ h) oxygen utilization rate - RQ = CPR/OUR respiratory quotient - S kg/m³ substrate concentration - t h,min, s time - t _u min recirculation time - t _M min mixing time - v m³/h volumetric flow rate through the loop - X kg/m³ (dry) cell mass concentration - Y _X/S yield coefficient of cell mass with regard to the consumed substrate - Y _X/DOC yield coefficient of the cell mass with regard to the consumed DOC - Y _X/O yield coefficient of the cell mass with regard to the consumed oxygen - Z relative distance in the tower from the aerator with regard to the height of the aerated broth - l/h specific growth rate - _m l/h maximum specific growth rate Indices f feed - e outlet