Maize feedstocks with improved digestibility reduce the costs and environmental impacts of biomass pretreatment and saccharification.

Background: Despite the recognition that feedstock composition influences biomass conversion efficiency, limited information exists as to how bioenergy crops with reduced recalcitrance can improve the economics and sustainability of cellulosic fuel conversion platforms. We have compared the bioenergy potential-estimated as total glucose productivity per hectare (TGP)-of maize cultivars contrasting for cell wall digestibility across processing conditions of increasing thermochemical severity. In addition, exploratory environmental impact and economic modeling were used to assess whether the development of bioenergy feedstocks with improved cell wall digestibility can enhance the environmental performance and reduce the costs of biomass pretreatment and enzymatic conversion.

Quantitative modeling and analytic assessment of the transcription dynamics of the XlnR regulon in Aspergillus niger.

Background: Transcription of genes coding for xylanolytic and cellulolytic enzymes in Aspergillus niger is controlled by the transactivator XlnR. In this work we analyse and model the transcription dynamics in the XlnR regulon from time-course data of the messenger RNA levels for some XlnR target genes, obtained by reverse transcription quantitative PCR (RT-qPCR). Induction of transcription was achieved using low (1 mM) and high (50 mM) concentrations of D-xylose (Xyl).

Correct positioning of central venous catheters using a new electric method.

Purpose: In order to find the correct final position of the tip of a central venous catheter, we have developed a new electric method (the Proximity of Cardiac Motion (PCM) method), designed to work in tandem with the existing ECG-based method.

Methods: A small, patient-safe, high-frequency current is fed through the catheter (via the saline-filled lumen of the catheter, or a stylet). Simultaneously, the resulting voltage is measured by two electrodes on the frontal thoracic skin.

Evaluation of design strategies for time course experiments in genetic networks: case study of the XlnR regulon in Aspergillus niger.

One of the challenges in genetic network reconstruction is finding experimental designs that maximize the information content in a data set. In this paper, the information value of mRNA transcription time course experiments was used to compare experimental designs. The study concerns the dynamic response of genes in the XlnR regulon of Aspergillus niger, with the goal to find the best moment in time to administer an extra pulse of inducing D-xylose.

d-Xylose concentration-dependent hydrolase expression profiles and the function of CreA and XlnR in Aspergillus niger.

Aspergillus niger is an important organism for the production of industrial enzymes such as hemicellulases and pectinases. The xylan-backbone monomer, d-xylose, is an inducing substance for the coordinate expression of a large number of polysaccharide-degrading enzymes. In this study, the responses of 22 genes to low (1 mM) and high (50 mM) d-xylose concentrations were investigated.

Modeling and analysis of the dynamic behavior of the XlnR regulon in Aspergillus niger.

Background: In this paper the dynamics of the transcription-translation system for XlnR regulon in Aspergillus niger is modeled. The model is based on Hill regulation functions and uses ordinary differential equations. The network response to a trigger of D-xylose is considered and stability analysis is performed.

Scaling-up vaccine production: implementation aspects of a biomass growth observer and controller.

This study considers two aspects of the implementation of a biomass growth observer and specific growth rate controller in scale-up from small- to pilot-scale bioreactors towards a feasible bulk production process for whole-cell vaccine against whooping cough. The first is the calculation of the oxygen uptake rate, the starting point for online monitoring and control of biomass growth, taking into account the dynamics in the gas-phase. Mixing effects and delays are caused by amongst others the headspace and tubing to the analyzer.

Online automatic tuning and control for fed-batch cultivation.

Performance of controllers applied in biotechnological production is often below expectation. Online automatic tuning has the capability to improve control performance by adjusting control parameters. This work presents automatic tuning approaches for model reference specific growth rate control during fed-batch cultivation.