Analysis of various sugars by means of immobilized enzyme coupled flow injection analysis

Fluorescence spectroscopy and chemometric modeling for bioprocess monitoring

On-line sensors for the detection of crucial process parameters are desirable for the monitoring, control and automation of processes in the biotechnology, food and pharma industry. Fluorescence spectroscopy as a highly developed and non-invasive technique that enables the on-line measurements of substrate and product concentrations or the identification of characteristic process states. During a cultivation process significant changes occur in the fluorescence spectra. By means of chemometric modeling, prediction models can be calculated and applied for process supervision and control to provide increased quality and the productivity of bioprocesses. A range of applications for different microorganisms and analytes has been proposed during the last years. This contribution provides an overview of different analysis methods for the measured fluorescence spectra and the model-building chemometric methods used for various microbial cultivations. Most of these processes are observed using the BioView® Sensor, thanks to its robustness and insensitivity to adverse process conditions. Beyond that, the PLS-method is the most frequently used chemometric method for the calculation of process models and prediction of process variables.

Enzymeless determination of total sugar by luminol-tetrachloroaurate chemiluminescence on chip to analyze food samples

Chemiluminescence (CL) emission from luminol-tetrachloroaurate ([AuCl(4)](-)) system studied in presence of monosaccharide sugars such as glucose and fructose was investigated on a microfluidic chip fabricated by the soft lithography technique. CL emission from the luminol-[AuCl(4)](-) system at 430 nm was intensified remarkably by the catalytic activity of glucose and fructose at room temperature. Under optimized conditions, the CL emission intensity of the system was found to be linearly related to the concentration of the sugars. Based on this observation, nonenzymatic determination of total sugar (glucose, fructose, or hydrolyzable sucrose) was performed in a rapid and sensitive analytical method. The results revealed that the linearity ranged from 9 to 1,750 μM for glucose and 80 to 1,750 μM for fructose, with a limit of detection of 0.65 and 0.69 μM, respectively. The relative standard deviations determined at 250 μM based on six repetitive injections were 1.13 and 1.15% for glucose and fructose, respectively. The developed method was successfully applied for determination of the total sugar concentration in food and beverages.

Engineering of pyranose 2-oxidase from Peniophora gigantea towards improved thermostability and catalytic efficiency

To improve the stability and catalytic efficiency of pyranose 2-oxidase (P2Ox) by molecular enzyme evolution, we cloned P2Ox cDNA by RACE-PCR from a cDNA library derived from the basidiomycete Peniophora gigantea. The P2Ox gene was expressed in Escherichia coli BL21(DE3), yielding an intracellular and enzymatically active P2OxB with a volumetric yield of 500 units/l. Site-directed mutagenesis was employed to construct the P2Ox variant E540K (termed P2OxB1), which exhibited increased thermo- and pH-stability compared with the wild type, concomitantly with increased catalytic efficiencies (k(cat)/K(m)) for D-xylose and L-sorbose. P2OxB1 was provided with a C-terminal His(6)-tag (termed P2OxB1H) and subjected to directed evolution using error-prone PCR. Screening based on a chromogenic assay yielded the new P2Ox variant K312E (termed P2OxB2H) that showed significant improvements with respect to k(cat)/K(m) for D-glucose (5.3-fold), methyl-beta-D-glucoside (2.0-fold), D-galactose (4.8-fold), D-xylose (59.9-fold), and L-sorbose (69.0-fold), compared with wild-type P2Ox. The improved catalytic performance of P2OxB2H was demonstrated by bioconversions of L-sorbose that initially was a poor substrate for wild-type P2Ox. This is the first report on the improvement of a pyranose 2-oxidase by a dual approach of site-directed mutagenesis and directed evolution, and the application of the engineered P2Ox in bioconversions.

Progress in monitoring, modeling and control of bioprocesses during the last 20 years

The paper gives a review on the recent development of bioprocess engineering. It includes monitoring of product formation processes by flow injection analysis, various types of chromatographic and spectroscopic methods as well as by biosensors. The evaluation of mycelial morphology and physiology by digital image analysis is discussed also. It deals with advanced control of indirectly evaluated process variables by means of state estimation/observer, with the use of structured and hybrid models, expert systems and pattern recognition for process optimization and gives a short report on the state of the art of metabolic flux analysis and metabolic engineering.

Amperometric flow-injection determination of sucrose with a mediated tri-enzyme electrode based on sucrose phosphorylase and electrocatalytic oxidation of NADH

A new sucrose electrode is described for the determination of sucrose without interference from glucose or fructose. The sucrose electrode is based on the tri-enzymatic system of sucrose phosphorylase, phosphoglucomutase and glucose-6-phosphate 1-dehydrogenase, where NAD(P)H is produced from the last enzymatic reaction and recycled into NAD(P)+ through its electrocatalytic oxidation by Os(4,4'-dimethyl-2,2-bypyridine)2(1,10-phenanthroline-5,6-dione). The electrodes were optimised with respect to the various construction parameters and carrier composition in a FIA system and their response as a function of the pH and flow-rate was examined. The electrodes were suitable for operation in a FIA system and the analysis of real samples showed good agreement with the reference method. Typical optimised electrodes showed detection limits of 1 mM sucrose, response time of 5 min, sensitivity 1.010 nA mM(-1), and current density of 8.38 microA cm(-2), using 200 mM PIPES pH 7.25 with 10 mM phosphate and 5 mM MgCl2 as carrier.

On-line and off-line monitoring of the production of cephalosporin C by Acremonium chrysogenum

Process monitoring of cephalosporin C formation by Acremonium chrysogenum in laboratory investigations is considered. The goal of these investigations is the identification of bottlenecks in the biosynthesis and the improvement of the process performance. Based on reports of other research groups and own experience the key parameters were selected, which influence the process performance. They are: dissolved oxygen and pH values. In addition the concentrations of biomass, DNA, glucose and reducing sugars (glucose, maltose, maltotriose and oligosaccharides), methionine, other nitrogen sources (ammonium ion, other amino acids), organic acids, phosphate, sulfate, dissolved organic carbon, proteins, product and precursors in the cell free cultivation medium are monitored. In addition the intracellular concentrations of RNA, DNA, proteins, amino acids as well as the activities of the enzymes of the biosynthesis of cephalosporin C are determined. The influence of these parameters on the biosynthesis is discussed.

Flow injection analysis system for the supervision of industrial chromatographic downstream processing in biotechnology

Sugar beet molasses is a natural resource for various products used in daily life, ranging from sucrose to amino acids for pharmaceutical industry. The separation of molasses into these high value components is performed on a large scale by ion exchange/exclusion chromatography. A biosensor system was set up for the "in time" analysis of serine and sucrose during molasses desugarisation. D-Serine was analysed with the multi-enzyme system D-serine dehydratase/lactic dehydrogenase and photometric detection of the NADH consumed. Sucrose was determined with invertase/mutarotase/glucose oxidase and the oxygen consumed was monitored amperometrically. An analysis could be performed within 2-5 min by directly injecting samples from the chromatographic process into the flow injection analysis system. The determination range for the sucrose analysis was 0-2.5 gl-1 and for the analysis of D-serine 0-0.5 gl-1. The standard deviation for the measurement of D-serine was 1.7%.

Influence of the process parameters on the morphology and enzyme production of Aspergilli

Several papers have been published dealing with various fungi to determine their morphology, enzyme production or process performance. However, no publication considered all of these aspects simultaneously. In the case of the production of xylanase by Aspergillus awamori the interrelationship of various key parameters are investigated. The influence of the reactor type (shake flasks, stirred tank and airlift tower loop reactor), the medium composition (semisynthetic and complex medium with wheat bran of different sizes, respectively as well as different concentrations of phosphate), and the specific power input (stirrer speed) on the growth, morphology, physiology, and productivity of the fungus are investigated. The results reveal a complex interrelationship which explains why the published results are contradictory. Without considering all of the relevant parameters, it is not possible to make general conclusions.

Influence of the medium composition and plasmid combination on the growth of recombinant Escherichia coli JM109 and on the production of the fusion protein EcoRI::SPA

Plasmid-free and plasmid-harbouring E. coli JM109 strains were investigated in shaken flasks, stirred tanks in batch and continuous operation. The shaken flask cultivations were performed in M9 minimal medium and in media with various protein supplements. The host hardly grows on M9 minimal medium as opposed to the plasmid-harbouring cells, which grow well on this medium. All of the investigated cells propagate well on protein-containing media. The influence of the combinations of repressor plasmid pRK248cI, the protection plasmid EcoR4 and the production plasmid pMTC48 were determined on the initial specific growth rate of the E. coli JM109 without gene expression, on the yield coefficient of cell growth, acetate concentration and acetate yield coefficient in the yeast extract-containing (HM) medium. The influence of various media on the induction of the gene expression were evaluated. In cultivation media with protein supplement, the growth rate and yield coefficient increased. The variation of the volumetric and specific beta-lactamase activities with the cultivation time were determined in a stirred tank reactor in HM medium. With increasing dilution rate the process performance decreased. Simple relationships exist between the substrate uptake rate and the specific growth rate of the continuous cultivated cells in M9 and HM media. The influence of the dilution rate on the cell mass concentration, colony forming units, acetate formation, yield coefficients of growth and acetate formation, substrate uptake rate, CO2 production rate, ammonium formation rate and beta-lactamase activity in M9 and HM media were determined as well. Carbon balances of the batch and continuous cultivations indicated high carbon recoveries. On account of the higher growth rate of plasmid-harbouring cells than than of the plasmid-free cells, the behaviour of the investigated plasmid-free and plasmid-harbouring E. coli JM109 cells deviates from the published properties of other plasmid-free and plasmid-harbouring E. coli cells.

Fermentation monitoring and process control

The use of modern analytical online methods such as two-dimensional fluorescence measurements gives new insights into bioprocesses. With the resulting data, it is not only possible to better understand and document, for example, biotransformations, but also to develop efficient control strategies that lead to better productivity and lower costs.