Cephalosporium acremonium is used as industrial strains for production of the p-lactam antibiotic cephalosporin C (CPC). For decades, CPC yields have been increasedthrough development of better production strains by traditional strain mutation andselection procedures, even recombinant DNA technology. Among these breeding methods,the screening was essential. Traditionally, the screening methods are performed in shakeflasks. However, there are some disadvantages of traditional flask screening method. Themain drawbacks were low screening throughput and poor parallelity. These limit the wideapplication of the strain improvement strategies. Therefore, it is very necessary to establisha high throughput screening method for CPC high-producing strains.　　 This thesis was designed to investigate a high throughput screening strategy forscreening high-producing CPC mutants of Cephalosporium acremonium. The strategy wasbased on microtiter plates culture microorganisms and measure products. The feasibility ofmicrotiter plates replacing shake flasks for cultivation and that of turbidimetric assay byELISA reader replacing HPLC assay was evaluated. These factors included: (1) the effectsof different microtiter plate formats on the ability of oxygen transfer, liquid evaporationbiomass; (2) the parallelity of among wells of microtiter plates for oxygen transfer, liquidevaporation, cell growth; (3) the correlation between microtiter plates and shaking flask.The high throughput screening systems were verified by screening high-producing CPCmutants. The general conclusions were as follows.　　 1. 48-well microtiter plate was more appropriate for cultivate aerobic microorganism than widely used 96-well microtiter plate. There were higher oxygen transfer coefficient larger working volume, and smaller water evaporation ratio in 48-well microtiter plates than in 96-well microtiter plates. So 48-well microtiter plates were suggested for an aerobic fermentation of Cephalosporium acremonium.　　 2. The optimized filling medium volume in each well of 48-well microtiter plates was 1200yl, which has the same evaporative rate and dry biomass weight as that in shaking flasks. The KLa value also close to the results from shake flasks.　　 3. The CPC productivity in 48-well microtiter plates was in good correlation with that in 500ml shake flasks (Pearson factor: r=0.9337, p<0.01, n=10), though the productivity in 48-well microtiter plates is relatively lower than that in shake flasks.　　 4. It was observed that there are good parallelism among the wells of 48-well microplate for the evaporation rate, oxygen transfer capacity, biomass, with low relative standarddeviation So shake flasks culture can be replaced by microtiter plates cultures for evaluating the ability of mutants producing CPC. The culture conditions were optimized for the production of CPC in 48-well microtiter plates. 68 hours of seed cujture time, 10％ inoculums level, 144 hours (six days) of culture times were used.　　 5. High throughput turbidimetric assay was developed to quantify the CPC concentration at 600nm absorbance. CPC productivity of diversified strains by turbidimetric assay　　 was good correlation with that by HPLC assay (Pearson factor: r=0.951, p<0.01, n=12). Compared with HPLC method, turbidimetric method was not to be limited by number of samples. The optimized analysis conditions were as follows: CPC concentration range was from 10 t0 80U/ml, the inoculation volumes of indicator bacterial Alcalignesfeacalis were from 4％ to 6％ and culture periods were about four hours.　　 6. Based on isolating single colony after mixed culture and evaluation of mutant population and mentioned-above high throughput screening strategy, two mutants of Cephalosporium acremonium (2-C2; 2-C5) were selected. The volumetric productivity of CPC of Cephalosporium acremonium were7914; 8639U/ml in shake flasks, respectively, about246％, 26g％improvement compared with that of original strain. Thus, the development of this strategy is expected to accelerate the selection of superior CPC producing strains.