A. Chemical Agents for weed control need to be replaced with biological control agents for better environmental effect. B. Bed temperature of solid phase fermentation needs to be controlled from over-heating that will kill the biological process. A. This project will help the produciton of spores useful as biological control agents for weeds, insects and other undesirable agents in agriucltural practice. B. The technique of pressure pulsation will be tested and developed for controlling the bed temperature of solid phase fermentation used in producing large amounts of spores as biological control agents in agriuclture. OBJECTIVES: Chemical agents have been widely used for control of insects, weeds, and so on in agricultural practice. However, chemical agents also leave undesirable environmental side-effects. Biological control agents have been closely examined in recent years as substitutes of chemical agents. Spores of Colletotrichum truncatum have been found useful in controlling a troublsome weed Sesbania exaltata that has caused substantial losses in the production of cotton, rice and soybeans. The main objective of this project is to develop an efficient method for production of large quantities of spores of C. trancatum as a biological control agent, employing solid phase fermentation. Solid phase fermentation has, however, a number of technical difficulties, particularly, the difficulty in heat dissipation from large fermentation solid beds. A novel technique called "pressure pulsation" has been found to be able to enhance heat removal from solid beds. The specific objective of this project is to test the method of pressure pulsation in controlling the bed temperature used in producing spores of C. truncatum. APPROACH: Temperature distribution in a solid fermenting bed is non-uniform. A highly automated instrument system will be designed and used in monitoring and controllong the temperature in a fermenting bed of C. truncatum. It is intended to keep the bed temprature at different parts of a bed within a pre-set, allowed temperature range to enhance cell growth and spores formation. If most parts of the bed can be kept within the temperature range, the project can be considered a success. Water will be added to help remove heat by evaporation. The rate and direction of air flow in the bed will also be used as a means to help control the temperature. PROGRESS: 2004/05 TO 2004/12 This project has the objective of examining the effect of pressure pulsation (PP) on solid phase fermentation (SPF) in porous substrate beds. In small scale operations, heat generated by biological activities usually can dissipate quickly and good growth of the microorganisms takes place. When SPF is scaled up, it faces difficulties in temperature build-up and inadequate oxygen supply. Biologically generated heat that is not dissipated quickly can increase temperature high enough to kill the cells. Mycelium growth of fungal cells tends to form aggregates that get larger and larger. Meanwhile, cells in the interior of the aggregates may die because of oxygen starvation. The PI has applied PP to overcome the difficulties. An enclosed solid phase fermentation chamber is equipped with one air inlet and one outlet. On the outlet tube, an on-off valve is installed. When the valve is closed, air continues to flow into the chamber and the pressure inside the chamber increases. When the valve opens, gas inside the chamber will exit to reduce the pressure. This cyclic pressure variation is called PP. Without PP, the porous bed will have slow heat dissipation by conduction. PP creates convective flow that is more effective in removing heat. The convective flow also helps oxygen supply and removal of water vapor and gaseous metabolic products. The work plan involves two tasks. One is to get familiarized with Colletotrichum truncatum that forms spores useful as a biological control agent. The second task is to build an instrument system that can create PP and to use PP to enhance spore formation by C. truncatum. Conclusions of this completed Phase I project are: 1. PP enhances the growth and spore formation for C. truncatum cultivated on solid substrates. Under conditions of no PP, growth can seldom go beyond a depth of 4 inches of solid bed. With PP, growth and spores are uniformly distributed throughout deep beds. In 1-liter vessels, the spore formation under PP is 30-60 folds of that without PP. 2. A highly versatile and yet inexpensive instrument system has been constructed that can be used for screening and testing fungal growth under various condition. The system makes solid phase fermentation easy to conduct and is the equivalent of culture shaker for liquid submerged fermentation. IMPACT: 2004/05 TO 2004/12 The results may help developing solid phase fermentation processes to become commonly used for enhanced production of value added products. It can compete or supplement processes currently done mostly by liquid submerged fermentation
