Is there a place for nutrition-sensitive agriculture?

The focus of the review paper is to discuss how biotechnological innovations are opening new frontiers to mitigate nutrition in key agricultural crops with potential for large-scale health impact to people in Africa. The general objective of the Africa Biofortified Sorghum (ABS) project is to develop and deploy sorghum with enhanced pro-vitamin A to farmers and end-users in Africa to alleviate vitamin A-related micronutrient deficiency diseases. To achieve this objective the project technology development team has developed several promising high pro-vitamin A sorghum events. ABS 203 events are so far the most advanced and well-characterised lead events with about 12 µg ß-carotene/g tissue which would supply about 40-50 % of the daily recommended vitamin A at harvest. Through gene expression optimisation other events with higher amounts of pro-vitamin A, including ABS 214, ABS 235, ABS 239 with 25, 30-40, 40-50 µg ß-carotene/g tissue, respectively, have been developed. ABS 239 would provide twice recommended pro-vitamin A at harvest, 50-90 % after 3 months storage and 13-45 % after 6 months storage for children. Preliminary results of introgression of ABS pro-vitamin A traits into local sorghum varieties in target countries Nigeria and Kenya show stable introgression of ABS vitamin A into local farmer-preferred sorghums varieties. ABS gene Intellectual Property Rights and Freedom to Operate have been donated for use royalty free for Africa. Prior to the focus on the current target countries, the project was implemented by fourteen institutions in Africa and the USA. For the next 5 years, the project will complete ABS product development, complete regulatory science data package and apply for product deregulation in target African countries.

Comparison of the energetic efficiencies of hydrogen and oxychemicals formation in Klebsiella pneumoniae and Clostridium butyricum during anaerobic growth on glycerol.

Data for the anaerobic growth of Klebsiella pneumoniae DSM 2026 and Clostridium butyricum DSM 5431 on glycerol have been analyzed using the concept of material and available electron balances with consideration for hydrogen production. Models for the kinetics of energetic efficiencies of product formation under low residual glycerol are presented. For Klebsiella pneumoniae, the specific rates of electron transfer to the products were mainly significantly dependent on specific growth rate with the exception of ethanol and hydrogen which were also significantly non-growth associated. In the case of Clostridium butyricum, the rates were only growth rate dependent, except for hydrogen formation. The analysis also indicated that the production of 1,3-propanediol by Klebsiella pneumoniae was favoured by limitations other than glycerol limitation, while hydrogen generation was best under low residual glycerol and particularly in the presence of external 1,3-propanediol. Klebsiella pneumoniae appeared to be able to incorporate more of the available electrons of glycerol into hydrogen as compared with the Clostridium butyricum. The study demonstrates the need for properly considering H2 in models describing anaerobic processes.

Utilization of statistics and experimental design in data collection and analysis.

Application of experimental design techniques to Pirt's yield model shows that it is important to collect data at the lowest and highest specific growth rates. In the fed-batch fermentation process, values of specific growth rate can be varied from the maximum value at the start of the process to very low values near the end of the experiment. Candida utilis was cultivated using batch followed by fed-batch culture with glucose as the main source of carbon and energy. Values of substrate concentration, oxygen consumption, carbon dioxide evolution, liquid volume, flow rate cell concentration, and nitrogen concentration, which was an indirect measure of biomass, were measured. Least-squares estimates of the true biomass energetic yield and maintenance coefficient were obtained using a multivariate statistical analysis procedure referred to as the covariate adjustment procedure. Methods of selecting the best estimates using covariate adjustment are illustrated. The results show that useful parameter estimates with relatively short confidence intervals can be obtained using these statistical methods.

Maximum likelihood estimation of growth yields.

This work is concerned with statistical methods to estimate yield and maintenance parameters associated with microbial growth. For a given dilution rate, an experimenter typically measures substrate concentration, oxygen utilization rate, the rate of carbon dioxide evolution, and biomass concentration. These correlated response variables each contain information about the maintenance and yield parameters of interest. A maximum likelihood estimator which combines this correlated information for the yield and maintenance parameters is proposed, evaluated, and tested on literature data. Both point and interval estimators are considered.