Production of conidia of Beauvaria bassiana for control of malaria mosquitos
06 / 2007 - 06 / 2011
Introduction: Malaria is one of the most serious vector-borne infectious diseases worldwide. About 300 to 500 million people are infected and cause one to three million deaths per year, mostly young children. Malaria is transmitted from one person to another by the bite of the female Anopheles mosquitoes and this transmission can be reduced by preventing mosquito bites with mosquito nets, using insect repellents, by spraying insecticides inside houses and draining standing water that provides habitat for the aquatic larvae. An awareness of recent problems of insecticide resistance and their adverse effects on man and his environment have resulted in more commercial attention being given to biological control alternatives such as the in-house application of spores of entomopathogenic fungi. Entomopathogenic fungi such as Beauveria bassiana have potential for use in Tanzania according to the field work carried out previously. Simple, cheap and large-scale production system is required for country-wide application. Therefore, Solid state fermentation, SSF, plays a crucial role since fungi can easily grow in this system and produce better quality spores (conidia) in large quantities. Aim: The main objective of this project is to develop a simple, cheap and large-scale cultivation system for production of spores of B. bassiana using SSF in Tanzania. Previous studies showed that it is feasible to use hemp impregnated with a rich nutrient solution as a substrate for SSF. Therefore, our first goal is to select a suitable support material that has the same characteristics as hemp and is readily available in sufficient quantities in Tanzania. The second goal is to choose the cultivation system which is simple, and cheap to operate in Tanzania. Thereafter, the focus will be based on optimization of mass production of spores through better understanding of such SSF system. Research: Based on the sufficient availability of these support materials in Tanzania, the current research focuses on the use of sisal hemp, sugar cane bagasse, and rice husks as candidates for the selection of the best support for conidia production. The best support material must have the same or better physical characteristics compared to the hemp, which was shown to be a feasible support for SSF. The growth of B. bassiana was found to be severely affected by mixing. Therefore, the use of static system such as packed bed with forced aeration and trays/bags are considered as good alternatives to investigate different aspects of SSF that influence the fungus performance and mass production. Future research: Future research will focus on optimizing the productivity and on the development of a model to predict the possible aspects of SSF that influence its performance. Knowledge of the stoichiometry of growth and sporulation in SSF will be very useful in aiming for higher productivity. For commercial production in Tanzania, systems such as bags/trays can be an alternative due to their simplicity and low-tech. However, the problem lies in process control due to the occurrence of high gradients in such systems. A model will be such a useful tool to allow transport phenomena studies in such systems.