High ammonia nitrogen utilization yeast strains and their related enzyme activities

Abstract:

[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.