高氨氮利用酵母菌的筛选及相关酶活性

【背景】蛋白饲料的缺乏，促进了蛋白含量高、安全性能好的酵母类单细胞蛋白的研究与应用。【目的】筛选氨氮利用能力强的菌株，为单细胞蛋白的发酵提供优良菌株。【方法】从土壤、奶制品、水果采集样品分离酵母菌，根据形态学和分子生物学鉴定菌株，然后以硫酸铵为唯一氮源培养基，测定菌落大小、菌体干重、蛋白质含量，复筛氨氮利用率高的酵母菌，并对复筛菌株氨同化相关酶活性进行测定。【结果】经过形态学、分子生物学鉴定和氨氮利用能力评价，获得3株高氨氮利用的酵母菌，分别是胶红酵母(Rhodotorula mucilaginosa)、酿酒酵母(Saccharomyces cerevisiae)和戴尔有孢圆酵母(Torulaspora delbrueckii)。通过比较3株酵母菌的谷氨酸脱氢酶、谷氨酸合成酶、谷氨酰胺合成酶活性，酿酒酵母的3种酶活性最高，其次是胶红酵母。【结论】从奶酪和西瓜中分离的胶红酵母N5和酿酒酵母J1具有较强的氨氮利用能力以及酶活性，可为单细胞蛋白发酵提供优良菌株。

High ammonia nitrogen utilization yeast strains and their related enzyme activities

Background] The lack of protein feed has promoted the research and application of yeast single-cell protein with high protein content and good safety performance. Objective] In order to screen strains with strong ammonia nitrogen utilization ability, provide excellent strains for single-cell protein fermentation. Methods] Yeasts were isolated and identified from the soil, dairy products and fruits based on morphology and molecular biology. Then, with ammonium sulfate as the sole nitrogen source medium, the bacterial colony size, cell dry weight and protein content were determined, and the yeasts with high ammonia nitrogen utilization rate were rescreened. The enzyme activities related to ammonia assimilation of the rescreening strains were determined. Results] By morphological, molecular biological identification and ammonia nitrogen utilization ability evaluation, three strains of high ammonia nitrogen utilization were obtained, they were Rhodotorula mucilaginosa, Saccharomyces cerevisiae and Torulaspora delbrueckii. S. cerevisiae has the highest activities of glutamate dehydrogenase, glutamate synthetase, and glutamine synthetase, followed by R. mucilaginosa. Conclusion] R. mucilaginosa N5 and S. cerevisiae J1 isolated from cheese and watermelon have strong ammonia nitrogen utilization ability and enzyme activities, and can provide excellent strains for single cell protein fermentation.