Abstract:A caffeine-degrading fungus was isolated from the soil in Jinsha County，Bijie City，Guizhou Province.An analysis of its phenotypic characteristics，internal transcriptional spacer sequences，and phylogenetic tree revealed that the fungus was a homologous strain of Saccharomyces cerevisiae（strain Y-1）.Single-factor and response surface tests yielded a prediction equation for a response surface regression model that useing caffeine degradation rate as an index.According to the prediction equation，the optimal culture conditions for strain Y-1 were as follows：temperature 31.00℃，fermentation time 46.60 h，caffeine addition 0.50 mg/mL，strain addition 6.90%.Under these conditions，the caffeine degradation rate was（59.39±0.28）%.